- Email: [email protected]
Locomotor stimulation by acute propofol administration in rats: Role of the nitrergic system
Pharmacological Reports 67 (2015) 980–985
Contents lists available at ScienceDirect
Pharmacological Reports journal homepage: www.elsevier.com/locate/pharep
Original research article
Locomotor stimulation by acute propofol administration in rats: Role of the nitrergic system ¨ zc¸etin b, Onur O ¨ zlu¨ c, Burcu C¸evreli b, Tayfun Uzbay b,* Aysu H. Tezcan a, Ays¸e O a
Department of Anaesthesiology and Reanimation, Ankara Numune Training and Research Hospital, Ankara, Turkey Neuropsychopharmacology Application and Research Center (NPARC), U¨sku¨dar University, Istanbul, Turkey c Department of Anaesthesiology and Reanimation, Faculty of Medicine, Du¨zce University, Du¨zce, Turkey b
A R T I C L E I N F O
Article history: Received 26 October 2014 Received in revised form 21 February 2015 Accepted 5 March 2015 Available online 20 March 2015 Keywords: Propofol Locomotor activity Abuse and dependence Nitric oxide Rat(s)
A B S T R A C T
Background: The addictive potential of propofol has been scientifically discussed. Drugs’ psychostimulant properties that can be assessed via measurements of locomotor activity are linked to their addictive properties. No studies that have investigated the effects of propofol on locomotor activity have been reported to date. The present study sought to investigate the effects and possible mechanisms of action of propofol on locomotor activity in rats. Methods: Adult male albino Wistar rats (250–330 g) were used as subjects. The locomotor activities of the rats were recorded for 30 min immediately following intraperitoneal administration of propofol (20 and 40 mg/kg), saline or vehicle (n = 8 for each group). NG-nitro arginine methyl ester (L-NAME, 15– 60 mg/kg), a nitric oxide (NO) synthase inhibitor, and haloperidol (0.125–5 mg/kg), a non-specific dopamine receptor antagonist, were also administered to other groups of rats 30 min prior to the propofol (40 mg/kg) injections, and locomotor activity was recorded for 30 min immediately after propofol administration (n = 8 for each group). Results: Propofol produced significant increases in the locomotor activities of the rats in the first 5 min of the observation period [F(2,21) = 9.052; p < 0.001]. L-NAME [F(4,35) = 3.112; p = 0.02] but not haloperidol [F(4,35) = 2.440; p = 0.067] pretreatment blocked the propofol-induced locomotor hyperactivity. L-NAME did not cause any significant change in locomotor activity in naı¨ve rats [F(2,21) = 0.569; p = 0.57]. Conclusions: Our results suggest that propofol might cause a short-term induction of locomotor activity in rats and that this effect might be related to nitrergic but not dopaminergic mechanisms. ß 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.
Introduction Propofol (2,6-diisopropylphenol) is a short-acting intravenous anaesthetic drug that is widely used for anaesthesia induction and intensive care procedures, such as endoscopy, colonoscopy and short-term invasive surgical attempts, to provide dose-dependent sedation and hypnosis. Propofol also provides control of stress responses and has anticonvulsant and amnesic activities [1,2]. The addictive potential of propofol has been debated in scientific area since the early 90s. In 1992, Follett and Farley from Albany Medical Center in New York published a case-report describing an anaesthesiologist who initially self-administered propofol to relieve stress but later began to crave the drug
* Corresponding author. E-mail address: [email protected] (T. Uzbay).
[3]. Previously some reports have also been published that have indicated some pleasant effects upon wakening from propofol, including euphoria [4,5]. It has also been found that propofol induces pleasant mood changes in humans at subanaesthetic doses [6]. The addictive and abuse potential of propofol received increased attention following the death of Michael Jackson, who was a popular singer [7]. Indeed, several articles and case reports have highlighted the abuse and dependence potential of propofol, particularly among health professionals [8–13]. Some findings that have been obtained from experimental animals have also supported the idea that propofol might have addictive and abuse potential. For example, conditioned-place preference is induced by propofol administration in rats [14,15]. The anxiolytic effects of propofol have been demonstrated in rodents [16,17], and some anxiolytics, such as benzodiazepines and barbiturates, have abuse potential and cause physical dependence in experimental animals and
http://dx.doi.org/10.1016/j.pharep.2015.03.003 1734-1140/ß 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
humans [18]. The reinforcing effects of propofol have been tested in rats, mice and baboons using drug self-administration procedures. These studies have revealed that propofol has prominent reinforcing effects in baboons [19] and rats [20] but not in mice [21]. Furthermore, in a recent study, Lian et al. [22] suggested that the self-administration of propofol is mediated by dopamine D1 receptors in the nucleus accumbens (NAc) in rats. It has also been proposed that propofol might increase the excitation of the dopaminergic neurons of the ventral tegmental area (VTA), which is an important brain region for reward and addiction, by increasing afferent glutamatergic transmission, which is an important dynamic of physical dependence [22,23]. The psychostimulant properties of a drug can be assessed by measuring locomotor activity, and these psychostimulant effects have been linked to the addictive properties of the drug [24]. The acute administration of psychostimulant agents, such as cocaine [25], amphetamine [26] and caffeine [27,28], induces locomotor stimulation and produces significant increases in open-field locomotor activity in rodents. Low and stimulant doses of ethanol also produce locomotor stimulant effects in rodents [29,30]. All of these agents cause dependence in abusers. Although propofol is an anaesthetic agent that is generally classified as a depressant, examinations of the effects of propofol on locomotor activity might yield interesting results. No studies that have investigated the effects of propofol on locomotor activity have yet been published. The major objective of the present study was to investigate the effects of propofol on locomotor activity in rats. We also aimed to explain possible mechanisms of action of the effects of propofol on locomotor activity. To these ends, we recorded the locomotor activities of rats after the administration of propofol, propofol plus NG-nitro arginine methyl ester (L-NAME, nitric oxide (NO) synthase inhibitor), and haloperidol (a non-specific dopamine receptor antagonist).
Materials and methods Animals and the laboratory All procedures in the present study were performed in accordance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health (USA) and the Declaration of Helsinki. Local ethical committee approval was also obtained. Adult male (250–330 g) albino Wistar rats were ¨ sku¨dar used as subjects. The animals were obtained from U University Experimental Research Unit (USKUDAB) and housed eight per cage in Plexiglas cages. The rats were placed in a quiet and temperature- and humidity-controlled room (22 2 8C and 60 5%, respectively) in which a 12/12-hour light-dark cycle was maintained (light from 7.00 a.m. to 7.00 p.m.). Food and water were available ad libitum. All experiments were performed at the same time of day during the light period (9.00 a.m.–11.00 a.m.). Drugs Propofol was purchased from Fresenius Kabi Austria GmbH (Graz, Austria). The doses of propofol were administered intraperitoneally (ip) to the animals from direct pharmaceutical preparations in the same volume of 0.5 ml/250 g. L-NAME was purchased from Sigma Chemical (St. Louis, MO, USA) and dissolved in 0.9% saline. Haloperidol was also purchased from Sigma Chemical (St. Louis, MO, USA) and dissolved in 0.1% dimethyl sulfoxide (DMSO). DMSO was purchased from the Biomatic Corporation (Wilmington, DE, USA). L-NAME, haloperidol, saline and vehicle were injected ip in volumes of 1 ml/kg. Drug stocks were prepared fresh every morning.
981
Apparatus Locomotor activity was measured with an open-field activity monitoring system (MAY 9908 model-Activity Monitoring SystemCommat Ltd., Ankara, Turkey). This system had eight Plexiglas cages (42 cm 42 cm 30 cm) equipped with infrared photocells. Fifteen photocell emitter and detector pairs were located 2 cm above the floor at intervals of 2.5 cm on opposite sides of each activity cage, and another 15 photocell pairs were located 8 cm above the floor. Interruptions of the photocell beams were detected by a computer system, and the location of the animal was calculated by the software at a temporal resolution of 0.1 s. If the calculated locations completely changed, these changes were interpreted as ambulatory activity. Other behavioural responses that caused interruptions of beams but not changes in location were recorded as horizontal activity. Vertical activity, such as rearing, was detected by the photocells located 8 cm above the cage floor. Procedure Animals were randomly assigned to the drug regimens (n = 8 for each group) and tested in a random order. Propofol (20 and 40 mg/ kg) and saline were injected ip to the first three groups of the rats. Because our preliminary experiments revealed that doses of propofol greater than 40 mg/kg did not produce any locomotor stimulation and elicited hypnotic activity immediately after the injections, the propofol dose of 40 mg/kg was selected for further experiments. For the combination treatments, L-NAME (15, 30 and 60 mg/kg) and haloperidol (0.125, 0.25 and 0.5 mg/kg) were injected into rats 30 min before propofol (40 mg/kg) administration. Immediately following the propofol injections and the final saline or vehicle injections (for the control groups), the rats were placed into the activity cages, and locomotor activity was measured for 30 min. Locomotor activity was recorded as the total of the horizontal, vertical and ambulatory activities of the rats. In a preliminary work, we observed that increases in the locomotor activities of the rats peaked within 5 min of the propofol injections. Therefore, we used a 5-min observation period to evaluate the effects of the drugs. To evaluate the effects of L-NAME (15–60 mg/kg) and haloperidol (0.125–0.5 mg/kg) in naive rats, the drugs and saline or vehicle were also administered to eight independent groups of subjects (n = 8 for each group), and the locomotor activities were recorded according to the same protocol. Statistics The data are expressed as the means SEMs. The data, including the effects of the propofol and combinations doses on the total locomotor activity over 5 min, were evaluated with one-way ANOVA tests. The effects of L-NAME and haloperidol on locomotor activity in the naı¨ve rats were also analysed with one-way ANOVAs. Tukey’s tests were used for all post hoc analyses. The level of statistical significance was set at p < 0.05. Results Effects of propofol on the locomotor activities of the rats The 30 min effects of propofol as divided in every 5 min on locomotor activity are shown in Fig. 1. The changes in the locomotor activities of the rats over the 5 min following propofol treatment are shown in Fig. 2. A one-way ANOVA test indicated a significant effect [F(2,21) = 9.052;
982
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
Fig. 1. Effects of propofol on locomotor activity for a 30 min period (*p < 0.05 significantly different from control).
Fig. 3. Effects of L-NAME on propofol (40 mg/kg)-induced locomotor hyperactivity in rats over 5 min (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control; #p < 0.05 significantly different from propofol treatment, Tukey’s test).
p < 0.001] on locomotor activity. Post hoc analyses revealed that the locomotor activity of the 40 mg/kg propofol-treated group was significantly greater than that of the saline-treated control rats between 0 and 5 min of the observation period (Tukey’s test, p = 0.005; Fig. 2). The propofol dose of 40 mg/kg was selected for the combination treatments.
Tukey’s test). The other doses of L-NAME did not produce any significant changes in the locomotor stimulation (p = 0.51 and 0.96, Tukey’s’ test; Fig. 3). Haloperidol pre-treatment did not produce any significant change in the propofol (40 mg/kg)-induced locomotor hyperactivity of the rats [F(4,35) = 2.440; p = 0.067, one-way ANOVA test] (Fig. 4).
Effects of L-NAME and haloperidol on propofol-induced locomotor stimulation in rats
Effects of L-NAME and haloperidol on the locomotor activity of naı¨ve rats
The effects of L-NAME and haloperidol treatment on the propofol (40 mg/kg)-induced locomotor stimulation in the rats have been shown in Figs. 3 and 4, respectively. L-NAME pretreatment produced some significant changes in the propofol-induced locomotor hyperactivity of the rats [F(4,35) = 3.112; p = 0.02, one-way ANOVA test]. L-NAME significantly blocked the locomotor stimulation of the rats at the 60-mg/kg dose (p = 0.04,
Finally, neither L-NAME (30 and 60 mg/kg) nor haloperidol (0.125–0.5 mg/kg) caused any significant changes in the locomotor activity of the naı¨ve (i.e., never administered propofol) rats [F(2,21) = 0.569; p = 0.57 and F(3,28) = 1.873; p = 0.157, respectively, one-way ANOVA test] (Figs. 5 and 6). Because a post hoc Tukey’s test revealed a significant inhibition of the locomotor
Fig. 2. Effects of propofol and saline on the locomotor activity of rats (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control).
Fig. 4. Effects of haloperidol on propofol (40 mg/kg)-induced locomotor hyperactivity in the rats over 5 min (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control).
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
Fig. 5. Effects of haloperidol on locomotor activity in drug naı¨ve rats (n = 8 for each group; *p < 0.05 significantly different from control vehicle).
activity at the 0.5-mg/kg dose of haloperidol (p = 0.038), we did not use higher doses of haloperidol in the combination treatments. Discussion This study is the first to investigate the effects of propofol on locomotor activity. The results of the present study clearly showed the anaesthetic agent propofol produced short-term (5-min) locomotor stimulation in rats immediately following treatment at the dose of 40 mg/kg. This propofol-induced locomotor hyperactivity was blocked by L-NAME, which is a -inhibiting agent, but not by haloperidol, which is a non-selective dopamine receptor antagonist. The inhibitory effect of L-NAME was not due to other non-specific effects related to its psychotropic properties, such as sedation or muscle relaxation, because it did not cause any
Fig. 6. Effects of L-NAME on locomotor activity in drug naı¨ve rats (n = 8 for each group).
983
significant impairments of locomotor activity in the naı¨ve rats in the present study. Thus, the inhibitory effects of L-NAME on the locomotor hyperactivity induced by L-NAME were specific. Overall, our results imply that NO might provide a significant contribution to propofol-induced short-term locomotor stimulation in rats. The propofol-induced locomotor hyperactivity could not have been related to any artefact of animal handling or the injection procedures because we used parallel control animals that were treated with the same protocol. The propofol-induced hyperactivity also did not appear to be due to the awkwardness, confusion or disorientation of the animals as they began to enter a state of anaesthesia. We carefully observed that all of the animals were awake and active during this time. Propofol-induced locomotor hyperactivity slowly decreased within this time and returned the normal levels. Thus, this dose of propofol did not cause any anaesthetic effects in the rats, and our observations of locomotor hyperactivity cannot be related to the initiation of a state of anaesthesia or anaesthesia induction. The combination doses of L-NAME and haloperidol used in our study and their administration times were selected based on the results of our preliminary experiments and previous studies [31,32]. In our study, we observed that the locomotor stimulating effect of propofol was prominent for the first 5 min following the injections and gradually decreased thereafter; thus, we selected a 5-min observation period to evaluate the effects of propofol on locomotor hyperactivity. Because our findings revealed significant increases in locomotor activity due to 40 mg/kg doses of propofol within the first 5 min of the observation period, this dose was used in further experiments. Haloperidol produced significant sedative effects beginning at the dose of 0.5 mg/kg. Thus, doses of haloperidol above 0.5 mg/kg were not tested in the combination experiments. Even the sedative dose of haloperidol failed to block the propofol-induced locomotor stimulation. The abuse and dependence potentials of propofol have been widely discussed in the scientific literature. In a comparatively recent review from the Utah Poison Control Center in the USA, Wilson et al. recommended that the U.S. Drug Enforcement Administration and other international agencies consider propofol a controlled substance [13]. Despite substantial evidence, this agent has not yet been listed as a controlled substance in many countries. In contrast, although findings from several experimental and clinical studies have implied that propofol has abuse and dependence potentials, some experimental behavioural laboratory investigations of the addictive potential of this agent remain unperformed. For example, whether propofol has locomotor stimulant effects similar to those of other addictive agents has not yet been evaluated. Obviously, many addictive agents, such as amphetamine [26], cocaine [25], nicotine [31], caffeine [27] and ethanol [33], produce locomotor stimulation in rodents, and these effects are directly related to their addictive properties [24]. Thus, measurements of the locomotor activity of rodents are worthwhile tools for evaluating the addictive potentials of suspect agents; in the present study, the effects of propofol on locomotor activity were investigated and evaluated with a detailed experimental protocol. Several lines of experimental evidence indicated that propofol interacts with the brain’s dopaminergic system, which is a key constituent of the rewarding effects of addictive agents. The associations of reinforcement and drug reward with the mesolimbic dopamine system are well established. The mesolimbic dopamine system is a crucially important part of the neuronal pathways that modulate addictive behaviour. The dopaminergic system originates in the VTA and terminates in NAc. All agents of abuse enhance the activity of this dopamine pathway of reward [34]. In previous experimental studies, propofol have been found to increase dopamine levels in the NAc [35], and self-administration
984
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
of the agent augments reinforcement via dopamine D1 receptors [22], which suggests that the propofol might modify the activity of dopamine neurons in the mesolimbic system. Because dopaminergic agonists and dopamine-activating agents produce locomotor stimulation and sensitisation in rodents [30,36,37], one could expect propofol to induce locomotor stimulation in rats. Although we observed a significant increase in locomotor activity following 40 mg/kg doses of propofol, the effect was not dose-dependent or sustained for a long period. We observed short-term (5-min) locomotor stimulation following single doses of propofol. However, if propofol prominently interacts with the mesolimbic dopamine system, similar to other reinforcing stimulants, a more consistent, dose-dependent and long-term effect on locomotor activity would be expected. Additionally, the non-selective dopamine receptor antagonist haloperidol did not block the short-term locomotor stimulation induced by propofol even at a high dose that induced sedation. This finding does not support the hypothesis that propofol causes locomotor stimulation via dopaminergic receptors. Grasshoff et al. [38] also reported that propofol administration by reverse microdialysis into the ventral pallidum (VP), which is the output structure of the NAc in the ventral cortico-striato-thalamo-cortical loop, decreases dopamine levels in this brain area of rats. Additionally, propofol has also been found to be ineffective in self-administration tests in mice [21]. The effects of propofol on the dopaminergic system might exhibit different properties depending on the administration route, the animal and the dose. Interestingly, we observed a dramatic increase in locomotor activity of DMSO (vehicle) plus propofol group as compared to saline plus propofol. Because DMSO itself also caused the similar effects on locomotor activity, this effect seems to be involved in vehicle-induced locomotor stimulation rather than an interaction between DMSO and propofol. Evidence suggests that NO might play an important role in substance abuse and dependence [39]. It has previously been suggested that the NO system is involved in mediating the anaesthetic effect of propofol [40]. Inhibition of the enzyme NOS has been reported to inhibit ethanol-induced locomotor sensitisation [41]. It has also been demonstrated that neuronal NOS knockout mice are resistant to the rewarding effects of ethanol [42,43]. Moreover, several studies have shown that NOS inhibitors attenuate the locomotor hyperactivity or locomotor sensitisation that is induced by amphetamine [26], nicotine [31], caffeine [27] and ethanol [30]. We observed that L-NAME, a NOS-inhibiting agent, significantly and dose-dependently blocked the propofolinduced locomotor hyperactivity but did not affect locomotor activity in naı¨ve rats. These findings clearly support the idea that propofol produces locomotor stimulation in rats via NO-related mechanisms. Our observations are also in line with results that have indicated the role of NO in the locomotor stimulation that is elicited by some addictive drugs. We do not know how the NOS inhibitor ameliorated the locomotor-stimulating effect of propofol. One interesting possible explanation of the inhibitory effects of L-NAME on propofolinduced locomotor stimulation is related to interactions with glutamatergic mechanisms that are mediated via NO. The activation of glutamate receptors, primarily of the NMDA subtype, causes an influx of calcium into neurons that leads to calmodulindependent activation of NOS [44]. Thus, the activation of NMDA receptors might be accompanied by the formation of NO [45]. It has previously been shown that propofol enhances NMDA-induced neuronal damage in rat hippocampal slices [46] and increases glutamatergic excitatory synaptic transmission in rat coronal midbrain slices [23]. NMDA antagonists are also known to block the locomotor hyperactivity induced by psychostimulants such as cocaine [25] and nicotine [47] in rodents. Overall, the locomotor
stimulant effects of propofol might also be explained via its effects on the NO-NMDA cascade. However, in contrast to this hypothesis, Kozinn et al. [48] suggested that propofol possesses the ability to inhibit NMDA receptor activation. Moreover, propofol also interacts with GABA receptors [49,50] that are important targets of addictive agents and addiction [51]. However, an association with the nitrergic mechanisms of this interaction is indefinite. Further studies are needed to clarify the exact mechanism of the locomotor stimulant effect of propofol. Presently, we can suggest that there is a significant relationship between the locomotor stimulant effect of propofol and the central nitrergic system. In conclusion, the present study revealed the relationship between the acute locomotor-stimulating effects of propofol and nitrergic but not dopaminergic mechanisms. Because locomotor stimulation and central NO are associated with addiction [24,39], our data might also provide evidence supporting the significance of propofol in mechanisms of dependence. Conflicts of interest The authors declare that there are no conflicts of interest. Funding This study was partially funded and supported by the Scientific and Technological Research Council of Turkey Turkish Scientific and Technological Research Council (TUBITAK, Turkey; Project No: 105S387, SBAG-3194). Acknowledgments The authors wish to thank Dr. Hakan Kayir, Dr. Sema Sanal Bas and Dr. Serhat Ozekes for their valuable comments and Mr. Emre Karaca for his technical assistance. The language of the manuscript has been revised and corrected by Elsevier Language Editing Service (UK). References [1] Baker MT. The anticonvulsant effects of propofol and a propofol analog, 2,6diisopropyl-4-(1-hydroxy-2,2,2-trifluoroethyl)phenol, in a 6 Hz partial seizure model. Anesth Analg 2011;112(2):340–4. [2] Fulton B, Propofol Sorkin EM. An overview of its pharmacology and a review of its clinical efficacy in intensive care sedation. Drugs 1995;50(4):636–57. [3] Follette JW, Farley WJ. Anesthesiologist addicted to propofol. Anesthesiology 1992;77(4):817–8. [4] Gepts E, Claeys MA, Camu F, Smekens L. Infusion of propofol (Diprivan) as sedative technique for colonoscopies. Postgrad Med J 1985;61(Suppl. 3): 120–6. [5] Grant IS, Mackenzie N. Recovery following propofol (Diprivan) anaesthesia – a review of three different anaesthetic techniques. Postgrad Med J 1985;61 (Suppl. 3):133–7. [6] Borgeat A, Wilder-Smith OH, Suter PM. The nonhypnotic therapeutic applications of propofol. Anesthesiology 1994;80(3):642–56. [7] Monroe T, Hamza H, Stocks G, Scimeca PD, Cowan R. The misuse and abuse of propofol. Subst Use Missue 2011;46(9):1199–205. [8] Bonnet U, Harkener J, Scherbaum N. A case report of propofol dependence in a physician. J Psychoactive Drugs 2008;40(2):215–7. [9] Bonnet U, Scherbaum N. Craving dominates propofol addiction of an affected physician. J Psychoactive Drugs 2012;44(2):186–90. [10] Earley PH, Finver T. Addiction to propofol: a study of 22 treatment cases. J Addict Med 2013;7(3):169–76. [11] Fritz GA, Niemczyk WE. Propofol dependency in a lay person. Anesthesiology 2002;96(2):505–6. [12] Roh S, Park JM, Kim DJ. A case of propofol dependence after repeated use for endoscopy. Endoscopy 2011;43(Suppl. 2). UCTN:E362. [13] Wilson C, Canning P, Caravati EM. The abuse potential of propofol. Clin Toxicol 2010;48(3):165–70. [14] Pain L, Oberling P, Sandner G, Di Scala G. Effect of propofol on affective state as assessed by place conditioning paradigm in rats. Anesthesiology 1996;85(1): 121–8. [15] Pain L, Oberling P, Sandner G, Di Scala G. Effect of midazolam on propofolinduced positive affective state assessed by place conditioning in rats. Anesthesiology 1997;87(4):935–43.
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985 [16] Barros-Pereira M, Pego JM, Sousa N. Anxiolytic effects of propofol with nonsedative doses. Eur J Anaestiol 2005;22:138. [17] Kurt M, Bilge SS, Kukula O, Celik S, Kesim Y. Anxiolytic-like profile of propofol, a general anesthetic, in the plus-maze test in mice. Pol J Pharmacol 2003;55(6):973–7. [18] Schuckit MA. Drug and alcohol abuse: a clinical guide to diagnosis and treatment. 5th ed. New York: Kluwer Academic/Plenum Publishers; 2000. p. 28–53. [19] Weerts EM, Ator NA, Griffiths RR. Comparison of the intravenous reinforcing effects of propofol and metohexital in baboons. Drug Alcohol Depend 1999; 57(1):51–60. [20] Le Sage MG, Stafford D, Glowa JR. Abuse liability of the anaesthetic propofol: self-administration of propofol in rats under fixed-ratio schedules of drug delivery. Psychopharmacology 2000;153(1):148–54. [21] Blokhina EA, Dravolina OA, Bespalov AY, Balster RL, Zvartu EE. Intravenous self-administration of abused solvents and anesthetics in mice. Eur J Pharmacol 2004;485(1-3):211–8. [22] Lian Q, Wang B, Zhou W, Jin S, Xu L, Huang Q, et al. Self-administration of propofol is mediated by dopamine D1 receptors in nucleus accumbens in rats. Neuroscience 2013;231(February):373–83. [23] Li K-Y, Xiao C, Xiong M, Delphin E, Ye J-H. Nanomolar propofol stimulates glutamate transmission to dopamine neurons: a possible mechanism of abuse potential. J Pharmacol Exp Ther 2008;325(1):165–74. [24] Wise RA, Bozarth MA. A psychomotor stimulant theory of addiction. Psychol Rev 1987;94(4):469–92. [25] Uzbay IT, Wallis CJ, Lal H, Forster MJ. Effects of NMDA receptor blockers on cocaine-stimulated locomotor activity in mice. Behav Brain Res 2000;108(1): 57–61. [26] Celik T, Zagli U, Kayir H, Uzbay IT. Nitric oxide synthase inhibition blocks amphetamine-induced locomotor activity in mice. Drug Alcohol Depend 1999;56(2):109–13. [27] Kayir H, Uzbay IT. Evidence for the role of nitric oxide in caffeine-induced locomotor activity in mice. Psychopharmacology 2004;172(1):11–5. [28] Uzbay T, Kose A, Kayir H, Ulusoy G, Celik T. Sex-related effects of agmatine on caffeine-induced locomotor activity in Swiss Webster mice. Eur J Pharmacol 2010;630(1–3):69–73. [29] Frye GD, Breese GR. An evaluation of the locomotor stimulating action of ethanol in rats and mice. Psychopharmacology 1981;75(4):372–9. [30] Uzbay IT, Kayir H. Bromocriptine and quinpirole but not 7-OH-DPAT and SKF 38393 potentiate the inhibitory effect of L-NAME on ethanol-induced locomotor activity in mice. Naunyn-Schmi Arch Pharmacol 2003;367(4):414–21. [31] Ulusu U, Uzbay IT, Kayir H, Alici T, Karakas S. Evidence for the role of nitric oxide in nicotine-induced locomotor sensitization in mice. Psychopharmacology 2005;178(4):500–4. [32] Wright JM, Dobosiewicz MR, Clarke PB. The role of dopaminergic transmission through D1-like and D2-like receptors in amphetamine-induced rat ultrasonic vocalizations. Psychopharmacology 2013;225(4):853–68. [33] Ozden O, Kayir H, Ozturk Y, Uzbay T. Agmatine blocks ethanol-induced locomotor hyperactivity in male mice. Eur J Pharmacol 2011;659(1):26–9. [34] Nestler EJ. Is there a common molecular pathway for addiction? Nat Neurosci 2005;8(11):1445–9.
985
[35] Pain L, Gobaille S, Schleef C, Aunis D, Oberling P. In vivo dopamine measurements in the nucleus accumbens after nonanesthetic and anesthetic doses of propofol in rats. Anest Analg 2002;95(4):915–9. [36] Amos S, Chindo BA, Abbah J, Vongtau HO, Edmond I, Binda L, et al. Postsynaptic dopamine D2-mediated behavioural effects of high acute doses of artemisinin in rodents. Brain Res Bull 2003;62(3):255–60. [37] Kayir H, Ceyhan M, Yavuz O, Uzbay IT. Lack of effect of Nomega-nitro-Larginine methyl ester on bromocriptine-induced locomotor sensitization in mice. Synapse 2007;61(10):869–75. [38] Grasshoff C, Herrera-Marschitz M, Goiny M, Kretschmer BD. Modulation of ventral pallidal dopamine and glutamate release by the intravenous anesthetic propofol studied by in vivo microdialysis. Amino Acids 2005; 28(2):145–8. [39] Uzbay IT, Oglesby MW. Nitric oxide and substance dependence. Neurosci Biobehav Rev 2001;25(1):43–52. [40] Tonner PH, Scholz J, Lamberz L, Schlamp N, Schulte am Esch J. Inhibition of nitric oxide synthase decreases anesthetic requirements of intravenous anesthetics in Xenopus laevis. Anesthesiology 1997;87(6):1479–85. [41] Itzhak Y, Martin JL. Blockade of alcohol-induced locomotor sensitization and conditioned place preference in DBA mice by 7-nitroindazole. Brain Res 2000;858(2):402–7. [42] Itzhak Y, Anderson KL. Ethanol-induced behavioral sensitization in adolescent and adult mice: role of the nNOS gene. Alcohol Clin Exp Res 2008;32(10): 1839–49. [43] Itzhak Y, Roger-Sa´nchez C, Anderson KL. Role of the nNOS gene in ethanolinduced conditioned place preference in mice. Alcohol 2009;43(4):285–91. [44] Garthwaite J, Garthwaite G, Palmer RM, Moncada S. NMDA receptor activation induces nitric oxide synthesis from arginine in rat brain slices. Eur J Pharmacol 1989;172(4–5):413–6. [45] Garthwaite J. Glutamate, nitric oxide and cell-cell signaling in the nervous system. Trends Neurosci 1991;14(2):60–7. [46] Zhu H, Cottrell JE, Kass IS. The effect of thiopental and propofol on NMDAand AMPA-mediated glutamate excitotoxicity. Anesthesiology 1997;87(4): 944–51. [47] Kosowski AR, Cebers G, Cebere A, Swanhagen AC, Liljequist S. Nicotineinduced dopamine release in the nucleus accumbens is inhibited by the novel AMPA antagonist ZK200775 and the NMDA antagonist CGP39551. Psychopharmacology 2004;175(1):114–23. [48] Kozinn J, Mao L, Yang L, Fibuch EE, Wang JQ. Inhibition of glutamatergic activation of extracellular signal-regulated protein kinases in hippocampal neurons by the intravenous anesthetic propofol. Anesthesiology 2006;105(6): 1182–91. [49] Ito H, Watanabe Y, Isshiki A, Uchino H. Neuroprotective properties of propofol and midazolam, but not pentobarbital, on neuronal damage induced by forebrain ischemia, based on the GABAA receptors. Acta Anaesthesiol Scand 1999;43(2):153–62. [50] Schwieler L, Delbro D, Engberg G, Erhardt S. The anaesthetic agent propofol interacts with GABA(B)-receptors: an electrophysiological study in rat. Life Sci 2003;72(24):2793–801. [51] Nutt D, Lingford-Hughes A. Addiction: the clinical interface. Br J Pharmacol 2008;154(2):397–405.
Contents lists available at ScienceDirect
Pharmacological Reports journal homepage: www.elsevier.com/locate/pharep
Original research article
Locomotor stimulation by acute propofol administration in rats: Role of the nitrergic system ¨ zc¸etin b, Onur O ¨ zlu¨ c, Burcu C¸evreli b, Tayfun Uzbay b,* Aysu H. Tezcan a, Ays¸e O a
Department of Anaesthesiology and Reanimation, Ankara Numune Training and Research Hospital, Ankara, Turkey Neuropsychopharmacology Application and Research Center (NPARC), U¨sku¨dar University, Istanbul, Turkey c Department of Anaesthesiology and Reanimation, Faculty of Medicine, Du¨zce University, Du¨zce, Turkey b
A R T I C L E I N F O
Article history: Received 26 October 2014 Received in revised form 21 February 2015 Accepted 5 March 2015 Available online 20 March 2015 Keywords: Propofol Locomotor activity Abuse and dependence Nitric oxide Rat(s)
A B S T R A C T
Background: The addictive potential of propofol has been scientifically discussed. Drugs’ psychostimulant properties that can be assessed via measurements of locomotor activity are linked to their addictive properties. No studies that have investigated the effects of propofol on locomotor activity have been reported to date. The present study sought to investigate the effects and possible mechanisms of action of propofol on locomotor activity in rats. Methods: Adult male albino Wistar rats (250–330 g) were used as subjects. The locomotor activities of the rats were recorded for 30 min immediately following intraperitoneal administration of propofol (20 and 40 mg/kg), saline or vehicle (n = 8 for each group). NG-nitro arginine methyl ester (L-NAME, 15– 60 mg/kg), a nitric oxide (NO) synthase inhibitor, and haloperidol (0.125–5 mg/kg), a non-specific dopamine receptor antagonist, were also administered to other groups of rats 30 min prior to the propofol (40 mg/kg) injections, and locomotor activity was recorded for 30 min immediately after propofol administration (n = 8 for each group). Results: Propofol produced significant increases in the locomotor activities of the rats in the first 5 min of the observation period [F(2,21) = 9.052; p < 0.001]. L-NAME [F(4,35) = 3.112; p = 0.02] but not haloperidol [F(4,35) = 2.440; p = 0.067] pretreatment blocked the propofol-induced locomotor hyperactivity. L-NAME did not cause any significant change in locomotor activity in naı¨ve rats [F(2,21) = 0.569; p = 0.57]. Conclusions: Our results suggest that propofol might cause a short-term induction of locomotor activity in rats and that this effect might be related to nitrergic but not dopaminergic mechanisms. ß 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.
Introduction Propofol (2,6-diisopropylphenol) is a short-acting intravenous anaesthetic drug that is widely used for anaesthesia induction and intensive care procedures, such as endoscopy, colonoscopy and short-term invasive surgical attempts, to provide dose-dependent sedation and hypnosis. Propofol also provides control of stress responses and has anticonvulsant and amnesic activities [1,2]. The addictive potential of propofol has been debated in scientific area since the early 90s. In 1992, Follett and Farley from Albany Medical Center in New York published a case-report describing an anaesthesiologist who initially self-administered propofol to relieve stress but later began to crave the drug
* Corresponding author. E-mail address: [email protected] (T. Uzbay).
[3]. Previously some reports have also been published that have indicated some pleasant effects upon wakening from propofol, including euphoria [4,5]. It has also been found that propofol induces pleasant mood changes in humans at subanaesthetic doses [6]. The addictive and abuse potential of propofol received increased attention following the death of Michael Jackson, who was a popular singer [7]. Indeed, several articles and case reports have highlighted the abuse and dependence potential of propofol, particularly among health professionals [8–13]. Some findings that have been obtained from experimental animals have also supported the idea that propofol might have addictive and abuse potential. For example, conditioned-place preference is induced by propofol administration in rats [14,15]. The anxiolytic effects of propofol have been demonstrated in rodents [16,17], and some anxiolytics, such as benzodiazepines and barbiturates, have abuse potential and cause physical dependence in experimental animals and
http://dx.doi.org/10.1016/j.pharep.2015.03.003 1734-1140/ß 2015 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier Sp. z o.o. All rights reserved.
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
humans [18]. The reinforcing effects of propofol have been tested in rats, mice and baboons using drug self-administration procedures. These studies have revealed that propofol has prominent reinforcing effects in baboons [19] and rats [20] but not in mice [21]. Furthermore, in a recent study, Lian et al. [22] suggested that the self-administration of propofol is mediated by dopamine D1 receptors in the nucleus accumbens (NAc) in rats. It has also been proposed that propofol might increase the excitation of the dopaminergic neurons of the ventral tegmental area (VTA), which is an important brain region for reward and addiction, by increasing afferent glutamatergic transmission, which is an important dynamic of physical dependence [22,23]. The psychostimulant properties of a drug can be assessed by measuring locomotor activity, and these psychostimulant effects have been linked to the addictive properties of the drug [24]. The acute administration of psychostimulant agents, such as cocaine [25], amphetamine [26] and caffeine [27,28], induces locomotor stimulation and produces significant increases in open-field locomotor activity in rodents. Low and stimulant doses of ethanol also produce locomotor stimulant effects in rodents [29,30]. All of these agents cause dependence in abusers. Although propofol is an anaesthetic agent that is generally classified as a depressant, examinations of the effects of propofol on locomotor activity might yield interesting results. No studies that have investigated the effects of propofol on locomotor activity have yet been published. The major objective of the present study was to investigate the effects of propofol on locomotor activity in rats. We also aimed to explain possible mechanisms of action of the effects of propofol on locomotor activity. To these ends, we recorded the locomotor activities of rats after the administration of propofol, propofol plus NG-nitro arginine methyl ester (L-NAME, nitric oxide (NO) synthase inhibitor), and haloperidol (a non-specific dopamine receptor antagonist).
Materials and methods Animals and the laboratory All procedures in the present study were performed in accordance with the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health (USA) and the Declaration of Helsinki. Local ethical committee approval was also obtained. Adult male (250–330 g) albino Wistar rats were ¨ sku¨dar used as subjects. The animals were obtained from U University Experimental Research Unit (USKUDAB) and housed eight per cage in Plexiglas cages. The rats were placed in a quiet and temperature- and humidity-controlled room (22 2 8C and 60 5%, respectively) in which a 12/12-hour light-dark cycle was maintained (light from 7.00 a.m. to 7.00 p.m.). Food and water were available ad libitum. All experiments were performed at the same time of day during the light period (9.00 a.m.–11.00 a.m.). Drugs Propofol was purchased from Fresenius Kabi Austria GmbH (Graz, Austria). The doses of propofol were administered intraperitoneally (ip) to the animals from direct pharmaceutical preparations in the same volume of 0.5 ml/250 g. L-NAME was purchased from Sigma Chemical (St. Louis, MO, USA) and dissolved in 0.9% saline. Haloperidol was also purchased from Sigma Chemical (St. Louis, MO, USA) and dissolved in 0.1% dimethyl sulfoxide (DMSO). DMSO was purchased from the Biomatic Corporation (Wilmington, DE, USA). L-NAME, haloperidol, saline and vehicle were injected ip in volumes of 1 ml/kg. Drug stocks were prepared fresh every morning.
981
Apparatus Locomotor activity was measured with an open-field activity monitoring system (MAY 9908 model-Activity Monitoring SystemCommat Ltd., Ankara, Turkey). This system had eight Plexiglas cages (42 cm 42 cm 30 cm) equipped with infrared photocells. Fifteen photocell emitter and detector pairs were located 2 cm above the floor at intervals of 2.5 cm on opposite sides of each activity cage, and another 15 photocell pairs were located 8 cm above the floor. Interruptions of the photocell beams were detected by a computer system, and the location of the animal was calculated by the software at a temporal resolution of 0.1 s. If the calculated locations completely changed, these changes were interpreted as ambulatory activity. Other behavioural responses that caused interruptions of beams but not changes in location were recorded as horizontal activity. Vertical activity, such as rearing, was detected by the photocells located 8 cm above the cage floor. Procedure Animals were randomly assigned to the drug regimens (n = 8 for each group) and tested in a random order. Propofol (20 and 40 mg/ kg) and saline were injected ip to the first three groups of the rats. Because our preliminary experiments revealed that doses of propofol greater than 40 mg/kg did not produce any locomotor stimulation and elicited hypnotic activity immediately after the injections, the propofol dose of 40 mg/kg was selected for further experiments. For the combination treatments, L-NAME (15, 30 and 60 mg/kg) and haloperidol (0.125, 0.25 and 0.5 mg/kg) were injected into rats 30 min before propofol (40 mg/kg) administration. Immediately following the propofol injections and the final saline or vehicle injections (for the control groups), the rats were placed into the activity cages, and locomotor activity was measured for 30 min. Locomotor activity was recorded as the total of the horizontal, vertical and ambulatory activities of the rats. In a preliminary work, we observed that increases in the locomotor activities of the rats peaked within 5 min of the propofol injections. Therefore, we used a 5-min observation period to evaluate the effects of the drugs. To evaluate the effects of L-NAME (15–60 mg/kg) and haloperidol (0.125–0.5 mg/kg) in naive rats, the drugs and saline or vehicle were also administered to eight independent groups of subjects (n = 8 for each group), and the locomotor activities were recorded according to the same protocol. Statistics The data are expressed as the means SEMs. The data, including the effects of the propofol and combinations doses on the total locomotor activity over 5 min, were evaluated with one-way ANOVA tests. The effects of L-NAME and haloperidol on locomotor activity in the naı¨ve rats were also analysed with one-way ANOVAs. Tukey’s tests were used for all post hoc analyses. The level of statistical significance was set at p < 0.05. Results Effects of propofol on the locomotor activities of the rats The 30 min effects of propofol as divided in every 5 min on locomotor activity are shown in Fig. 1. The changes in the locomotor activities of the rats over the 5 min following propofol treatment are shown in Fig. 2. A one-way ANOVA test indicated a significant effect [F(2,21) = 9.052;
982
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
Fig. 1. Effects of propofol on locomotor activity for a 30 min period (*p < 0.05 significantly different from control).
Fig. 3. Effects of L-NAME on propofol (40 mg/kg)-induced locomotor hyperactivity in rats over 5 min (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control; #p < 0.05 significantly different from propofol treatment, Tukey’s test).
p < 0.001] on locomotor activity. Post hoc analyses revealed that the locomotor activity of the 40 mg/kg propofol-treated group was significantly greater than that of the saline-treated control rats between 0 and 5 min of the observation period (Tukey’s test, p = 0.005; Fig. 2). The propofol dose of 40 mg/kg was selected for the combination treatments.
Tukey’s test). The other doses of L-NAME did not produce any significant changes in the locomotor stimulation (p = 0.51 and 0.96, Tukey’s’ test; Fig. 3). Haloperidol pre-treatment did not produce any significant change in the propofol (40 mg/kg)-induced locomotor hyperactivity of the rats [F(4,35) = 2.440; p = 0.067, one-way ANOVA test] (Fig. 4).
Effects of L-NAME and haloperidol on propofol-induced locomotor stimulation in rats
Effects of L-NAME and haloperidol on the locomotor activity of naı¨ve rats
The effects of L-NAME and haloperidol treatment on the propofol (40 mg/kg)-induced locomotor stimulation in the rats have been shown in Figs. 3 and 4, respectively. L-NAME pretreatment produced some significant changes in the propofol-induced locomotor hyperactivity of the rats [F(4,35) = 3.112; p = 0.02, one-way ANOVA test]. L-NAME significantly blocked the locomotor stimulation of the rats at the 60-mg/kg dose (p = 0.04,
Finally, neither L-NAME (30 and 60 mg/kg) nor haloperidol (0.125–0.5 mg/kg) caused any significant changes in the locomotor activity of the naı¨ve (i.e., never administered propofol) rats [F(2,21) = 0.569; p = 0.57 and F(3,28) = 1.873; p = 0.157, respectively, one-way ANOVA test] (Figs. 5 and 6). Because a post hoc Tukey’s test revealed a significant inhibition of the locomotor
Fig. 2. Effects of propofol and saline on the locomotor activity of rats (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control).
Fig. 4. Effects of haloperidol on propofol (40 mg/kg)-induced locomotor hyperactivity in the rats over 5 min (n = 8 for each group; control: vehicle treatment; *p < 0.05 significantly different from control).
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
Fig. 5. Effects of haloperidol on locomotor activity in drug naı¨ve rats (n = 8 for each group; *p < 0.05 significantly different from control vehicle).
activity at the 0.5-mg/kg dose of haloperidol (p = 0.038), we did not use higher doses of haloperidol in the combination treatments. Discussion This study is the first to investigate the effects of propofol on locomotor activity. The results of the present study clearly showed the anaesthetic agent propofol produced short-term (5-min) locomotor stimulation in rats immediately following treatment at the dose of 40 mg/kg. This propofol-induced locomotor hyperactivity was blocked by L-NAME, which is a -inhibiting agent, but not by haloperidol, which is a non-selective dopamine receptor antagonist. The inhibitory effect of L-NAME was not due to other non-specific effects related to its psychotropic properties, such as sedation or muscle relaxation, because it did not cause any
Fig. 6. Effects of L-NAME on locomotor activity in drug naı¨ve rats (n = 8 for each group).
983
significant impairments of locomotor activity in the naı¨ve rats in the present study. Thus, the inhibitory effects of L-NAME on the locomotor hyperactivity induced by L-NAME were specific. Overall, our results imply that NO might provide a significant contribution to propofol-induced short-term locomotor stimulation in rats. The propofol-induced locomotor hyperactivity could not have been related to any artefact of animal handling or the injection procedures because we used parallel control animals that were treated with the same protocol. The propofol-induced hyperactivity also did not appear to be due to the awkwardness, confusion or disorientation of the animals as they began to enter a state of anaesthesia. We carefully observed that all of the animals were awake and active during this time. Propofol-induced locomotor hyperactivity slowly decreased within this time and returned the normal levels. Thus, this dose of propofol did not cause any anaesthetic effects in the rats, and our observations of locomotor hyperactivity cannot be related to the initiation of a state of anaesthesia or anaesthesia induction. The combination doses of L-NAME and haloperidol used in our study and their administration times were selected based on the results of our preliminary experiments and previous studies [31,32]. In our study, we observed that the locomotor stimulating effect of propofol was prominent for the first 5 min following the injections and gradually decreased thereafter; thus, we selected a 5-min observation period to evaluate the effects of propofol on locomotor hyperactivity. Because our findings revealed significant increases in locomotor activity due to 40 mg/kg doses of propofol within the first 5 min of the observation period, this dose was used in further experiments. Haloperidol produced significant sedative effects beginning at the dose of 0.5 mg/kg. Thus, doses of haloperidol above 0.5 mg/kg were not tested in the combination experiments. Even the sedative dose of haloperidol failed to block the propofol-induced locomotor stimulation. The abuse and dependence potentials of propofol have been widely discussed in the scientific literature. In a comparatively recent review from the Utah Poison Control Center in the USA, Wilson et al. recommended that the U.S. Drug Enforcement Administration and other international agencies consider propofol a controlled substance [13]. Despite substantial evidence, this agent has not yet been listed as a controlled substance in many countries. In contrast, although findings from several experimental and clinical studies have implied that propofol has abuse and dependence potentials, some experimental behavioural laboratory investigations of the addictive potential of this agent remain unperformed. For example, whether propofol has locomotor stimulant effects similar to those of other addictive agents has not yet been evaluated. Obviously, many addictive agents, such as amphetamine [26], cocaine [25], nicotine [31], caffeine [27] and ethanol [33], produce locomotor stimulation in rodents, and these effects are directly related to their addictive properties [24]. Thus, measurements of the locomotor activity of rodents are worthwhile tools for evaluating the addictive potentials of suspect agents; in the present study, the effects of propofol on locomotor activity were investigated and evaluated with a detailed experimental protocol. Several lines of experimental evidence indicated that propofol interacts with the brain’s dopaminergic system, which is a key constituent of the rewarding effects of addictive agents. The associations of reinforcement and drug reward with the mesolimbic dopamine system are well established. The mesolimbic dopamine system is a crucially important part of the neuronal pathways that modulate addictive behaviour. The dopaminergic system originates in the VTA and terminates in NAc. All agents of abuse enhance the activity of this dopamine pathway of reward [34]. In previous experimental studies, propofol have been found to increase dopamine levels in the NAc [35], and self-administration
984
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985
of the agent augments reinforcement via dopamine D1 receptors [22], which suggests that the propofol might modify the activity of dopamine neurons in the mesolimbic system. Because dopaminergic agonists and dopamine-activating agents produce locomotor stimulation and sensitisation in rodents [30,36,37], one could expect propofol to induce locomotor stimulation in rats. Although we observed a significant increase in locomotor activity following 40 mg/kg doses of propofol, the effect was not dose-dependent or sustained for a long period. We observed short-term (5-min) locomotor stimulation following single doses of propofol. However, if propofol prominently interacts with the mesolimbic dopamine system, similar to other reinforcing stimulants, a more consistent, dose-dependent and long-term effect on locomotor activity would be expected. Additionally, the non-selective dopamine receptor antagonist haloperidol did not block the short-term locomotor stimulation induced by propofol even at a high dose that induced sedation. This finding does not support the hypothesis that propofol causes locomotor stimulation via dopaminergic receptors. Grasshoff et al. [38] also reported that propofol administration by reverse microdialysis into the ventral pallidum (VP), which is the output structure of the NAc in the ventral cortico-striato-thalamo-cortical loop, decreases dopamine levels in this brain area of rats. Additionally, propofol has also been found to be ineffective in self-administration tests in mice [21]. The effects of propofol on the dopaminergic system might exhibit different properties depending on the administration route, the animal and the dose. Interestingly, we observed a dramatic increase in locomotor activity of DMSO (vehicle) plus propofol group as compared to saline plus propofol. Because DMSO itself also caused the similar effects on locomotor activity, this effect seems to be involved in vehicle-induced locomotor stimulation rather than an interaction between DMSO and propofol. Evidence suggests that NO might play an important role in substance abuse and dependence [39]. It has previously been suggested that the NO system is involved in mediating the anaesthetic effect of propofol [40]. Inhibition of the enzyme NOS has been reported to inhibit ethanol-induced locomotor sensitisation [41]. It has also been demonstrated that neuronal NOS knockout mice are resistant to the rewarding effects of ethanol [42,43]. Moreover, several studies have shown that NOS inhibitors attenuate the locomotor hyperactivity or locomotor sensitisation that is induced by amphetamine [26], nicotine [31], caffeine [27] and ethanol [30]. We observed that L-NAME, a NOS-inhibiting agent, significantly and dose-dependently blocked the propofolinduced locomotor hyperactivity but did not affect locomotor activity in naı¨ve rats. These findings clearly support the idea that propofol produces locomotor stimulation in rats via NO-related mechanisms. Our observations are also in line with results that have indicated the role of NO in the locomotor stimulation that is elicited by some addictive drugs. We do not know how the NOS inhibitor ameliorated the locomotor-stimulating effect of propofol. One interesting possible explanation of the inhibitory effects of L-NAME on propofolinduced locomotor stimulation is related to interactions with glutamatergic mechanisms that are mediated via NO. The activation of glutamate receptors, primarily of the NMDA subtype, causes an influx of calcium into neurons that leads to calmodulindependent activation of NOS [44]. Thus, the activation of NMDA receptors might be accompanied by the formation of NO [45]. It has previously been shown that propofol enhances NMDA-induced neuronal damage in rat hippocampal slices [46] and increases glutamatergic excitatory synaptic transmission in rat coronal midbrain slices [23]. NMDA antagonists are also known to block the locomotor hyperactivity induced by psychostimulants such as cocaine [25] and nicotine [47] in rodents. Overall, the locomotor
stimulant effects of propofol might also be explained via its effects on the NO-NMDA cascade. However, in contrast to this hypothesis, Kozinn et al. [48] suggested that propofol possesses the ability to inhibit NMDA receptor activation. Moreover, propofol also interacts with GABA receptors [49,50] that are important targets of addictive agents and addiction [51]. However, an association with the nitrergic mechanisms of this interaction is indefinite. Further studies are needed to clarify the exact mechanism of the locomotor stimulant effect of propofol. Presently, we can suggest that there is a significant relationship between the locomotor stimulant effect of propofol and the central nitrergic system. In conclusion, the present study revealed the relationship between the acute locomotor-stimulating effects of propofol and nitrergic but not dopaminergic mechanisms. Because locomotor stimulation and central NO are associated with addiction [24,39], our data might also provide evidence supporting the significance of propofol in mechanisms of dependence. Conflicts of interest The authors declare that there are no conflicts of interest. Funding This study was partially funded and supported by the Scientific and Technological Research Council of Turkey Turkish Scientific and Technological Research Council (TUBITAK, Turkey; Project No: 105S387, SBAG-3194). Acknowledgments The authors wish to thank Dr. Hakan Kayir, Dr. Sema Sanal Bas and Dr. Serhat Ozekes for their valuable comments and Mr. Emre Karaca for his technical assistance. The language of the manuscript has been revised and corrected by Elsevier Language Editing Service (UK). References [1] Baker MT. The anticonvulsant effects of propofol and a propofol analog, 2,6diisopropyl-4-(1-hydroxy-2,2,2-trifluoroethyl)phenol, in a 6 Hz partial seizure model. Anesth Analg 2011;112(2):340–4. [2] Fulton B, Propofol Sorkin EM. An overview of its pharmacology and a review of its clinical efficacy in intensive care sedation. Drugs 1995;50(4):636–57. [3] Follette JW, Farley WJ. Anesthesiologist addicted to propofol. Anesthesiology 1992;77(4):817–8. [4] Gepts E, Claeys MA, Camu F, Smekens L. Infusion of propofol (Diprivan) as sedative technique for colonoscopies. Postgrad Med J 1985;61(Suppl. 3): 120–6. [5] Grant IS, Mackenzie N. Recovery following propofol (Diprivan) anaesthesia – a review of three different anaesthetic techniques. Postgrad Med J 1985;61 (Suppl. 3):133–7. [6] Borgeat A, Wilder-Smith OH, Suter PM. The nonhypnotic therapeutic applications of propofol. Anesthesiology 1994;80(3):642–56. [7] Monroe T, Hamza H, Stocks G, Scimeca PD, Cowan R. The misuse and abuse of propofol. Subst Use Missue 2011;46(9):1199–205. [8] Bonnet U, Harkener J, Scherbaum N. A case report of propofol dependence in a physician. J Psychoactive Drugs 2008;40(2):215–7. [9] Bonnet U, Scherbaum N. Craving dominates propofol addiction of an affected physician. J Psychoactive Drugs 2012;44(2):186–90. [10] Earley PH, Finver T. Addiction to propofol: a study of 22 treatment cases. J Addict Med 2013;7(3):169–76. [11] Fritz GA, Niemczyk WE. Propofol dependency in a lay person. Anesthesiology 2002;96(2):505–6. [12] Roh S, Park JM, Kim DJ. A case of propofol dependence after repeated use for endoscopy. Endoscopy 2011;43(Suppl. 2). UCTN:E362. [13] Wilson C, Canning P, Caravati EM. The abuse potential of propofol. Clin Toxicol 2010;48(3):165–70. [14] Pain L, Oberling P, Sandner G, Di Scala G. Effect of propofol on affective state as assessed by place conditioning paradigm in rats. Anesthesiology 1996;85(1): 121–8. [15] Pain L, Oberling P, Sandner G, Di Scala G. Effect of midazolam on propofolinduced positive affective state assessed by place conditioning in rats. Anesthesiology 1997;87(4):935–43.
A.H. Tezcan et al. / Pharmacological Reports 67 (2015) 980–985 [16] Barros-Pereira M, Pego JM, Sousa N. Anxiolytic effects of propofol with nonsedative doses. Eur J Anaestiol 2005;22:138. [17] Kurt M, Bilge SS, Kukula O, Celik S, Kesim Y. Anxiolytic-like profile of propofol, a general anesthetic, in the plus-maze test in mice. Pol J Pharmacol 2003;55(6):973–7. [18] Schuckit MA. Drug and alcohol abuse: a clinical guide to diagnosis and treatment. 5th ed. New York: Kluwer Academic/Plenum Publishers; 2000. p. 28–53. [19] Weerts EM, Ator NA, Griffiths RR. Comparison of the intravenous reinforcing effects of propofol and metohexital in baboons. Drug Alcohol Depend 1999; 57(1):51–60. [20] Le Sage MG, Stafford D, Glowa JR. Abuse liability of the anaesthetic propofol: self-administration of propofol in rats under fixed-ratio schedules of drug delivery. Psychopharmacology 2000;153(1):148–54. [21] Blokhina EA, Dravolina OA, Bespalov AY, Balster RL, Zvartu EE. Intravenous self-administration of abused solvents and anesthetics in mice. Eur J Pharmacol 2004;485(1-3):211–8. [22] Lian Q, Wang B, Zhou W, Jin S, Xu L, Huang Q, et al. Self-administration of propofol is mediated by dopamine D1 receptors in nucleus accumbens in rats. Neuroscience 2013;231(February):373–83. [23] Li K-Y, Xiao C, Xiong M, Delphin E, Ye J-H. Nanomolar propofol stimulates glutamate transmission to dopamine neurons: a possible mechanism of abuse potential. J Pharmacol Exp Ther 2008;325(1):165–74. [24] Wise RA, Bozarth MA. A psychomotor stimulant theory of addiction. Psychol Rev 1987;94(4):469–92. [25] Uzbay IT, Wallis CJ, Lal H, Forster MJ. Effects of NMDA receptor blockers on cocaine-stimulated locomotor activity in mice. Behav Brain Res 2000;108(1): 57–61. [26] Celik T, Zagli U, Kayir H, Uzbay IT. Nitric oxide synthase inhibition blocks amphetamine-induced locomotor activity in mice. Drug Alcohol Depend 1999;56(2):109–13. [27] Kayir H, Uzbay IT. Evidence for the role of nitric oxide in caffeine-induced locomotor activity in mice. Psychopharmacology 2004;172(1):11–5. [28] Uzbay T, Kose A, Kayir H, Ulusoy G, Celik T. Sex-related effects of agmatine on caffeine-induced locomotor activity in Swiss Webster mice. Eur J Pharmacol 2010;630(1–3):69–73. [29] Frye GD, Breese GR. An evaluation of the locomotor stimulating action of ethanol in rats and mice. Psychopharmacology 1981;75(4):372–9. [30] Uzbay IT, Kayir H. Bromocriptine and quinpirole but not 7-OH-DPAT and SKF 38393 potentiate the inhibitory effect of L-NAME on ethanol-induced locomotor activity in mice. Naunyn-Schmi Arch Pharmacol 2003;367(4):414–21. [31] Ulusu U, Uzbay IT, Kayir H, Alici T, Karakas S. Evidence for the role of nitric oxide in nicotine-induced locomotor sensitization in mice. Psychopharmacology 2005;178(4):500–4. [32] Wright JM, Dobosiewicz MR, Clarke PB. The role of dopaminergic transmission through D1-like and D2-like receptors in amphetamine-induced rat ultrasonic vocalizations. Psychopharmacology 2013;225(4):853–68. [33] Ozden O, Kayir H, Ozturk Y, Uzbay T. Agmatine blocks ethanol-induced locomotor hyperactivity in male mice. Eur J Pharmacol 2011;659(1):26–9. [34] Nestler EJ. Is there a common molecular pathway for addiction? Nat Neurosci 2005;8(11):1445–9.
985
[35] Pain L, Gobaille S, Schleef C, Aunis D, Oberling P. In vivo dopamine measurements in the nucleus accumbens after nonanesthetic and anesthetic doses of propofol in rats. Anest Analg 2002;95(4):915–9. [36] Amos S, Chindo BA, Abbah J, Vongtau HO, Edmond I, Binda L, et al. Postsynaptic dopamine D2-mediated behavioural effects of high acute doses of artemisinin in rodents. Brain Res Bull 2003;62(3):255–60. [37] Kayir H, Ceyhan M, Yavuz O, Uzbay IT. Lack of effect of Nomega-nitro-Larginine methyl ester on bromocriptine-induced locomotor sensitization in mice. Synapse 2007;61(10):869–75. [38] Grasshoff C, Herrera-Marschitz M, Goiny M, Kretschmer BD. Modulation of ventral pallidal dopamine and glutamate release by the intravenous anesthetic propofol studied by in vivo microdialysis. Amino Acids 2005; 28(2):145–8. [39] Uzbay IT, Oglesby MW. Nitric oxide and substance dependence. Neurosci Biobehav Rev 2001;25(1):43–52. [40] Tonner PH, Scholz J, Lamberz L, Schlamp N, Schulte am Esch J. Inhibition of nitric oxide synthase decreases anesthetic requirements of intravenous anesthetics in Xenopus laevis. Anesthesiology 1997;87(6):1479–85. [41] Itzhak Y, Martin JL. Blockade of alcohol-induced locomotor sensitization and conditioned place preference in DBA mice by 7-nitroindazole. Brain Res 2000;858(2):402–7. [42] Itzhak Y, Anderson KL. Ethanol-induced behavioral sensitization in adolescent and adult mice: role of the nNOS gene. Alcohol Clin Exp Res 2008;32(10): 1839–49. [43] Itzhak Y, Roger-Sa´nchez C, Anderson KL. Role of the nNOS gene in ethanolinduced conditioned place preference in mice. Alcohol 2009;43(4):285–91. [44] Garthwaite J, Garthwaite G, Palmer RM, Moncada S. NMDA receptor activation induces nitric oxide synthesis from arginine in rat brain slices. Eur J Pharmacol 1989;172(4–5):413–6. [45] Garthwaite J. Glutamate, nitric oxide and cell-cell signaling in the nervous system. Trends Neurosci 1991;14(2):60–7. [46] Zhu H, Cottrell JE, Kass IS. The effect of thiopental and propofol on NMDAand AMPA-mediated glutamate excitotoxicity. Anesthesiology 1997;87(4): 944–51. [47] Kosowski AR, Cebers G, Cebere A, Swanhagen AC, Liljequist S. Nicotineinduced dopamine release in the nucleus accumbens is inhibited by the novel AMPA antagonist ZK200775 and the NMDA antagonist CGP39551. Psychopharmacology 2004;175(1):114–23. [48] Kozinn J, Mao L, Yang L, Fibuch EE, Wang JQ. Inhibition of glutamatergic activation of extracellular signal-regulated protein kinases in hippocampal neurons by the intravenous anesthetic propofol. Anesthesiology 2006;105(6): 1182–91. [49] Ito H, Watanabe Y, Isshiki A, Uchino H. Neuroprotective properties of propofol and midazolam, but not pentobarbital, on neuronal damage induced by forebrain ischemia, based on the GABAA receptors. Acta Anaesthesiol Scand 1999;43(2):153–62. [50] Schwieler L, Delbro D, Engberg G, Erhardt S. The anaesthetic agent propofol interacts with GABA(B)-receptors: an electrophysiological study in rat. Life Sci 2003;72(24):2793–801. [51] Nutt D, Lingford-Hughes A. Addiction: the clinical interface. Br J Pharmacol 2008;154(2):397–405.