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Evidence for the involvement of ionotropic glutamatergic receptors on the antinociceptive effect of (−)-linalool in mice
Neuroscience Letters 440 (2008) 299–303
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Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet
Evidence for the involvement of ionotropic glutamatergic receptors on the antinociceptive effect of (−)-linalool in mice Patr´ıcia Aparecida Batista a , Maria Fernanda de Paula Werner a , Erica Carvalho Oliveira b , Leonel Burgos c , Patricia Pereira c , Lucimar Filot da Silva Brum c , Adair Roberto Soares dos Santos b,∗ a b c
Department of Pharmacology, Center of Biological Science, Federal University of Santa Catarina, Florianopolis, SC, Brazil Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianopolis, SC, Brazil Postgraduate Programme in Genetics and Applied Toxicology, Lutheran University of Brazil, Porto Alegre, RS, Brazil
a r t i c l e
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Article history: Received 9 April 2008 Received in revised form 14 May 2008 Accepted 26 May 2008 Keywords: (−)-Linalool Glutamate Nociception Substance P NMDA receptor
a b s t r a c t (−)-Linalool is a monoterpene alcohol which is present in the essential oils of several aromatic plants. Recent studies suggest that (−)-linalool has anti-inflammatory, antihyperalgesic and antinociceptive properties in different animal models. The present study investigated the contribution of glutamatergic system in the antinociception elicited by (−)-linalool in mice. Nociceptive response was characterized by the time that the animal spent licking the injected hind paw or biting the target organ following glutamate receptor agonist injections. (−)-Linalool administered by intraperitoneal (i.p., 10–200 mg/kg), oral (p.o., 5–100 mg/kg) or intrathecal (i.t., 0.1–3 g/site) routes dose-dependently inhibited glutamate-induced nociception (20 mol/paw, pH 7.4) with ID50 values of 139.1 mg/kg; 34.6 mg/kg; and 0.9 g/site, with inhibitions of 70 ± 4; 72 ± 7 and 74 ± 8%, respectively. However, the intraplantar injection of (−)-linalool partially (49 ± 9%) inhibited glutamate-induced nociception. Furthermore, (−)-linalool (200 mg/kg) given i.p. also reduced significantly the biting response caused by intrathecal injection of glutamate (30 g/site), AMPA (25 ng/site), SP (135 ng/site), NMDA (25 ng/site) and kainate (23.5 ng/site), with inhibitions of 89 ± 6%, 73 ± 11%, 85 ± 4%, 98 ± 2% and 52 ± 15%, respectively. However, (−)-linalool did not inhibit nociception induced by intrathecal injection of trans-ACPD (8.6 g/site). Taken together, these results provide experimental evidences indicating that (−)-linalool produce marked antinociception against glutamate induced pain in mice, possible due mechanisms operated by ionotropic glutamate receptors, namely AMPA, NMDA and kainate. © 2008 Elsevier Ireland Ltd. All rights reserved.
Many plant-derived substances are attractive sources for developing new analgesic agents. Among these natural products, (−)-linalool (Fig. 1) is one natural occurring enantiomer monoterpene compound prevalent in essential oils of various aromatic plant species. Interestingly, experimental studies reported that (−)-linalool exhibit a variety of pharmacological effects, including anticonvulsant, anxiolytic, anti-inflammatory and antinociceptive effects [9,10,23]. In rats, some studies have shown that (−)-linalool reduced thermal hyperalgesia evoked by carrageenan, glutamate and PGE2 , as well as carrageenan-induced paw oedema and formalin-induced nociception, suggesting an important anti-inflammatory action for these essential oil [22]. Moreover, (−)-linalool displayed antinociceptive activity in acetic acid-induced visceral pain in mice, effect that involves activation of both opioidergic and cholinergic neu-
∗ Corresponding author. Tel.: +55 48 3721 9352; fax: +55 48 37219672. E-mail addresses: [email protected], [email protected] (A.R.S.d. Santos). 0304-3940/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2008.05.092
rotransmission [21]. More recently, it has been suggested that the antinociceptive effects of (−)-linalool could be related to the inhibition of nitric oxide (NO) synthesis and to adenosine A1 and A2A receptor-operated mechanisms [23,24]. Psychopharmacological studies have also shown that (−)linalool modulates glutamatergic neurotransmission both in vitro and in vivo conditions, possibly through N-methyl-d-aspartate (NMDA) receptor interactions [30,31]. Glutamate and glutamatergic receptors can be located in both central and peripheral nervous systems and are responsible for mediating most of the excitatory neurotransmission. Although there is some evidence demonstrating the antinociceptive action of (−)-linalool, we have not found any study investigating the effect of (−)-linalool on glutamate-induced pain. Glutamate receptors (GluRs) are divided in two major classes, designated ionotropic and metabotropic receptors, and both play an important role in modulating nociceptive processing at both peripheral and spinal levels [12,20]. The ionotropic receptors (iGluRs) are cation-specific ion channels, and are further
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Fig. 1. Molecular structure of monoterpene (−)-linalool.
subdivided into three groups: N-methyl-d-aspartate (NMDA), ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and kainate receptors. On the other hand, metabotropic receptors (mGluRs) are coupled to GTP-binding proteins (G-proteins), which modulate the production of second messengers [20]. There is a large evidence accumulated that substances capable of blocking both iGluR and mGluR exhibit pronounced antinociceptive and analgesic effects in several mammalian species including humans [6,15,19,27,32]. Therefore, it is supposed that substances capable of blocking GluRs may have clinical potential in the management of some painful states. However, the use of those substances as analgesics is hampered due to the unaccepted side effects observed by these drugs [17]. For this reason, it is believed that new drugs that block GluR with reduced side-effects may have potential clinical indications for some painful states. In light of these considerations, the current study aimed to investigate the ability of (−)-linalool to reduce glutamate-induced nociception in mice hind paw. Further, it was characterized the contribution of the spinal iGluRs- and mGluRs-operated mechanisms in the antinociception caused by (−)-linalool on the biting response caused by intrathecal (i.t.) injection of selective glutamate receptor agonists in mice. All experiments were performed on male Swiss mice (25–35 g), housed 20 to a cage under a 12-h light/12-h dark cycle (lights on at 6:00) in a controlled temperature room (22 ± 2 ◦ C) with free access to laboratory chow and tap water. Mice were acclimatized to the laboratory conditions for at least 1 h before testing that was carried on between 9:00 and 17:00 h. All experiments were conducted under the ethical guidelines of the International Association for the Study of Pain [33] and the experimental procedures were previously approved by the Committee on the Ethical Use of Animals of the UFSC, where the study was conducted. Animals were used only once throughout the experiments. The number of animals and intensities of noxious stimuli used were the minimum necessary to demonstrate the consistent effects of drug treatments. The substances used were l-glutamic acid hydrochloride (glutamate), substance P and (−)-linalool (Sigma Chemical Co., St Louis, USA); kainic acid (kainate), (±)-l-aminocylopentanetrans-1,3-dicarboxylic acid (tACPD), ␣-amino-3-hydoxy-5-methyl4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) (Tocris, Cookson Inc., Ellisville, USA). All drugs were dissolved immediately before administration in saline solution (0.9% NaCl). Glutamate was dissolved in isotonic saline solution, which had its pH adjusted to 7.4 by the addition of NaOH and (−)-linalool was dissolved in saline plus Tween 80. The final concentration of Tween 80 did not exceed 10% and did not cause any effects per se. The choice of the doses of each drug was based on literature data [11,26,29] or on preliminary experiments carried out in our laboratory (results not shown). In an attempt to provide more direct evidence concerning the possible interaction of (−)-linalool with the glutamatergic system, we investigated whether (−)-linalool would be able to antagonize glutamate-induced licking in the mouse paw. The procedure used was similar to describe previously [2]. Animals used were individ-
ually adapted into glass funnel. A volume of 20 l of glutamate (20 mol/paw) was injected intraplantarly (i.pl.) in the ventral surface to the right hind paw. The mice were observed individually for 15 min following glutamate injection. The amount of time the animals spent licking or biting the injected paw was measured with a chronometer and was considered as indicative of nociception. Mice were pre-treated with (−)-linalool by intraperitoneal (i.p. 10–200 mg/kg, 30 min beforehand), oral (p.o., 5–100 mg/kg, 60 min beforehand), intrathecal (i.t., 0.1–3 g/site, 15 min beforehand) or intraplantar (10–300 ng/paw, co-administered with glutamate) routes. Control animals received a similar volume of vehicle systemically (i.p. or p.o., 10 ml/kg), centrally (i.t., 5 l/site) or peripherally (20 l/paw, co-administered with glutamate) routes, before glutamate injection. In another set of experiments, the interaction of (−)-linalool with the glutamatergic system was investigated by using both ionotropic and metabotropic agonists of excitatory aminoacids (EAAs) receptors, which were administered by intrathecal (i.t.) route, causing biting behavior in mice [29]. Animals received (−)linalool (200 mg/kg, i.p.) 30 min before i.t. injection of 5 l of drugs. Injections were given to fully conscious mice using the method described by Hylden and Wilcox [13]. Briefly, the animals were restrained manually and a 30-gauge needle, attached to a 50-l microsyringe, was inserted through the skin and between the vertebrae into the subdural space of the L5–L6 spinal segments. The biting behavior was defined as a single head movement directed toward the lumbar and caudal region of spinal cord or hind limbs, resulting in contact of the animal’s snout with the target organ. Intrathecal injections were given over a period of 5 s. The nociceptive response was elicited by glutamate (30 g/site), AMPA (a selective agonist of AMPA-subtype of glutamatergic ionotropic receptors, 25 ng/site), NMDA (a selective agonist of NMDA-subtype of glutamatergic ionotropic receptors, 25 ng/site), kainate (a selective agonist of kainate-subtype of glutamatergic ionotropic receptors, 23.5 ng/site), trans-ACPD (an agonist of metabotropic glutamate receptors, 8.6 g/site) [29] or substance P (a selective NK1 agonists, 135 ng/site) [13]. As control, a group of mice received vehicle (saline) by i.t. route. The amount of time the mice spent biting the target organ was evaluated following local post-injections of one of the following agonists: glutamate 3 min; AMPA 1 min; NMDA 5 min; kainate 4 min; trans-ACPD 15 min [29] or substance P 6 min [13]. To evaluate some non-specific muscle-relaxant or sedative effects of (−)-linalool, mice were submitted to the rota-rod task [28]. The rota-rod apparatus consisted of a bar with a diameter of 2.5 cm, subdivided into four compartments by disks 25 cm in diameter. The bar rotated at a constant speed of 17 revolutions/min. The animals were selected 24 h previously by eliminating those mice which did not remain on the bar for three consecutive periods of 60 s. Animals were treated with (−)-linalool (10–200 mg/kg, i.p. or 0.1–3 g/site, i.t.) or vehicle (10 ml/kg, i.p. or 5 l/i.t.), 30 min (i.p.) and 10 min (i.t.) before the test. The results are expressed as the time in sets for which animals remained on the rota-rod. The cut-off time used was 60 s. The results are presented as mean ± S.E.M., except the ID50 values (i.e., the dose of (−)-linalool necessary to reduce the nociceptive response by 50% relative to the control value), which are reported as geometric means accompanied by their respective 95% confidence limits. The ID50 value was determined by linear regression from individual experiments using linear regression GraphPad software (GraphPad software, San Diego, CA, USA). Comparisons between experimental and control groups were performed by ANOVA followed by Newman–Keuls test when appropriated. P values less than 0.05 (P < 0.05) were considered as indicative of significance.
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Fig. 2. Effect of (−)-linalool administered intraperitoneally (A), orally (B), intraplantarly (C) or intrathecally (D) against licking induced by intraplantar injection of glutamate (20 mol/paw) in mice. Each column represents the mean of six to eight animals and the error bars indicate the S.E.M. Control values (C) indicate the animals injected with saline and the asterisks denote the significance levels *P < 0.05, ***P < 0.001 when compared with control groups values (one-way ANOVA followed by Newmann–Keuls test).
The results in Fig. 2 (A, B and D) show that (−)-linalool given either systemic (i.p. or p.o.) (5–200 mg/kg) or centrally (i.t.) (0.1–3 g/site), caused significant and dose-dependent inhibition of glutamate-induced nociception. The calculated mean ID50 values obtained by i.p., p.o. and i.t. routes were 139.1 mg/kg (107.3–180.4); 34.6 mg/kg (23.3–51.9) and 0.9 g/site (0.2–2.4), with inhibitions of 70 ± 4, 72 ± 7 and 74 ± 8%, respectively. While intraplantar treatment with (−)-linalool (10–300 ng/paw) partially (49 ± 9%) inhibited glutamate-induced nociception (Fig. 1C). Fig. 3 shows that (−)-linalool (200 mg/kg, i.p., 30 min before) also elicited a pronounced inhibition of the biting response induced by glutamate, AMPA, NMDA, kainate and substance P with inhibitions of 89 ± 6%, 73 ± 11%, 98 ± 2%, 52 ± 15% and 85 ± 4%, respectively. However, the same treatment did not prevent the bit-
Fig. 3. Effect of (−)-linalool (200 mg/kg) administered intraperitoneally on the biting response caused by intrathecal injection of glutamate (30 g/site), NMDA (25 ng/site), AMPA (25 ng/site), kainate (23.5 ng/site), trans-ACPD (8.6 g/site) and substance P (SP) (135 ng/site) in mice. Each column represents the means of six to eight animals and the error bars indicate the S.E.M. Asterisks denote the significance levels*P < 0.05; **P < 0.01 and ***P < 0.001 when compared with control group values (one-way ANOVA followed by Newmann–Keuls test).
ing response induced by the metabotropic glutamatergic receptor agonist trans-ACPD (Fig. 3). (−)-Linalool administered by i.p. (10, 50, 100 and 200 mg/kg) or i.t. (0.1, 0.3, 1.0 and 3.0 g/site) routes did not affect the motor performance on the rota-rod task when compared with animals that received vehicle (control group). The means values ± S.E.M. on the rota-rod task were 176.0 ± 4.0, 176.0 ± 2.5, 178.0 ± 2.0, 176.0 ± 2.5 and 180.0 ± 0.0 s for the i.p. treatment groups and control respectively, and 179.3 ± 0.3; 180.0 ± 0.0; 155.3 ± 24.7, 117.0 ± 30.5 and 179.7 ± 0.3 for the i.t. treatment groups and control, respectively. The results presented in the current study clearly demonstrate that (−)-linalool, the natural occurring enantiomer in essential oils, administered by systemic (oral and intraperitoneal), peripheral (intraplantar) or central (intrathecal) routes, produced significant inhibition of the behavioral nociceptive response caused by intraplantar injection of glutamate into the mouse hind paw. Moreover, the antinociceptive effect of (−)-linalool seems to be related with its ability to modulate ionotropic glutamate receptors (iGluR). It is well established that glutamate is involved in transmission of nociceptive signals from peripheral nervous system to the dorsal horn of the spinal cord. Moreover, it has been reported that the glutamate injection elicited marked nociceptive responses, that is mediated by neuropeptides (like SP) releasing from sensory fibers and due to activation of glutamate receptors (i.e. NMDA), that can stimulate the production of a variety of intracellular second messengers, such as NO [4]. In addition, Beirith et al. [2] have found that the nociceptive response induced by glutamate appears to involve peripheral, spinal and supraspinal sites of action and is greatly mediated by both NMDA and non-NMDA receptors. The results of this study extend previous data from other groups regarding (−)-linalool antinociceptive effect [21–23,14]. They clearly show, for the first time, that (−)-linalool, administered by i.p., p.o. and i.t. routes dose-dependently protects the mice from
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glutamate-induced nociception. On the other hand, the intraplantar injection of (−)-linalool also inhibited the nociception caused by glutamate, though not significantly. From these results, we can infer that the antinociception caused by (−)-linalool on the pro-algesic effect of glutamate involves peripheral and spinal sites of action. Interestingly, the oral administration of (−)-linalool was fourfold more potent in preventing the glutamate-induced nociception than the i.p. administration. We do not have an explanation for this; however, probably pharmacokinetics factors can be contributing to these effects. It is generally recognized that oral administration of (−)-linalool produces metabolites such as 8-hydroxy-linalool and 8-carboxy-linalool [5] but it remains to be seen if these metabolites have antinociceptive effect and additive effect towards (−)-linalool activity. On the other hand, intraplantar injection of (−)-linalool caused only partial inhibition on glutamate-induced nociception in mice hind paw. This result may be due the administration of both substances at the same time, which were different to the schedule used by others, administration routes. However, we cannot rule out the participation of peripheral glutamatergic receptors. The highest dose of (−)-linalool (200 mg/kg) administered by subcutaneous route also reduced thermal hyperalgesia induced by intraplantar injection of glutamate in rats [22]. However, there are marked differences in the methods used among this study and ours, mainly related to route of administration, those difficult comparisons. The treatment of mice with glutamate and selective ionotropic and metabotropic agonists of this excitatory aminoacid (EAA) receptors, we have confirmed previous data from the literature showing that intrathecal injection of glutamate, NMDA, AMPA, kainate and trans-ACPD results in pronounced biting responses ([29], for review see [3]). These results, together with studies using selective antagonists for all the subtypes of glutamate receptors, give further support for the view that NMDA, AMPA, kainate and metabotropic glutamatergic receptors play relevant roles in the establishment or maintenance of painful states (for review see [3,7]). The present results may indicate that, at least in part, the antinociceptive action caused by (−)-linalool in glutamate test could be due to an interaction with the glutamatergic system, more specifically via interaction with iGluR. This assertion is supported by the demonstration that (−)-linalool (200 mg/kg) administered i.p., a dose that produced significant effect on glutamate-induced paw licking, significantly attenuated the biting response induced by intrathecal injection of glutamate and NMDA and, to a lesser extent, that induced by AMPA and kainate. In this regard, it is noteworthy that (−)-linalool have an inhibitory effect on glutamate-binding sites in a competitive manner as well as an inhibitory effect on MK801-binding sites in a non-competitive manner to mouse cortex membranes [8]. In addition, it was also reported that (−)-linalool modulates glutamate activation expression in vitro (comparative antagonism of l-[3 H]glutamate binding) and in vivo (delayed subcutaneous N-methyl-d-aspartate (NMDA)-induced convulsions and blockade of intracerebroventricular quinolinic acid-induced convulsions) [30,31]. On the other hand, the lack of effect of (−)-linalool against intrathecal injection of the glutamatergic metabotropic agonist trans-ACPD, at doses which reduce substantially biting caused by iGluRs agonists, seems to exclude the possible contribution of mGluRs-operated mechanisms to this antinociceptive response. The findings showing that (−)-linalool do not possess any marked irritant effect at the doses and administration routes tested are also relevant. In addition, (−)-linalool given by intraperitoneal and intrathecal routes did not modify locomotor activity evaluated by rota-rod test, thus ruling out the influence of a possible sedative effect in the antinociceptive action.
A large body of evidence indicates an interaction of substance P and glutamate at the spinal level. The behaviour indicative of pain, which can be observed after spinal administration of substance P, is potentiated by co-administration of NMDA [18]. In addition, there are reports showing that pre-synaptic NMDA receptors located on the terminals of small-diameter pain fibers facilitate and prolong the transmission of nociceptive messages through the release of substance P and glutamate [14]. Therefore, an important crosstalk between glutamate and SP in pain transmission has been well documented in the literature [1,6,14,16,25]. Here we also demonstrate that (−)-linalool markedly attenuated the biting response induced by intrathecal injection of substance P. Corroborating with such observations we may speculate that (−)-linalool acting at NMDA receptors may reduce the pain behavior produced by substance P. In summary, these findings not only confirm but also greatly extend previous evidence from the literature which demonstrates that (−)-linalool, administered by peripheric, systemic and spinal routes, possess antinociceptive properties in mice. The antinociceptive effect of (−)-linalool involves peripheral and spinal sites of action and seems to be mediated by interaction with ionotropic glutamatergic-dependent mechanisms, via NMDA receptors. Finally, these results strength the notion that (−)-linalool might be used in the future for the management of pain. Acknowledgements This work was supported by grants from Conselho Nacional ´ de Desenvolvimento Cient´ıfico e Tecnologico (CNPq), Programa de ´ Apoio aos Nucleos de Excelˆencia (PRONEX), Fundac¸a˜ o de Apoio ´ a` Pesquisa Cient´ıfica Tecnologica do Estado de Santa Catarina (FAPESC) and Financiadora de Estudos e Projetos [FINEP, Rede Instituto Brasileiro de Neurociˆencia (IBN-Net)], Brazil. M.F.P. Werner is a Post-Doc fellow and P.A. Batista is PhD fellow. They thank CNPq and CAPES by fellowship support. References [1] A.W. Afrah, C.O. Stiller, L. Olgart, E. Brodin, H. Gustafsson, Involvement of spinal N-methyl-d-aspartate receptors in capsaicin-induced in vivo release of substance P in the rat dorsal horn, Neurosci. Lett. 316 (2000) 83–86. [2] A. Beirith, A.R.S. Santos, J.B. Calixto, Mechanisms underlying the nociception and paw oedema caused by injection of glutamate in the mouse paw, Brain Res. 924 (2002) 219–228. [3] D. Bleakman, A. Alt, E.S. Nisenbaum, Glutamate receptors and pain. Review article, Semin. Cell Dev. Biol. 17 (2006) 592–604. [4] S.M. Carlton, S. Zhou, R.E. Coggeshall, Evidence for the interaction of glutamate and NK1 receptors in the periphery, Brain Res. 2 (1998) 229–238. [5] A. Chadha, K.M. Madyastha, Metabolism of geraniol and linalool in the rat and effects on liver and lung microsomal enzymes, Xenobiotica 14 (1984) 365–374. [6] B.A. Chizh, Novel approaches to targeting glutamate receptors for the treatment of chronic pain: review article, Amino Acids 23 (2001) 169–176. [7] T.J. Coderre, I. Van Empel, The utility of excitatory amino acid (EAA) antagonists as analgesic agents. I. Comparison of the antinociceptive activity of various classes of EAA antagonists in mechanical, thermal and chemical nociceptive tests, Pain 59 (1994) 345–352. [8] E. Elisabetsky, J. Marschner, D.O. Souza, Effects of linalool on glutamatergic system in the rat cerebral cortex, Neurochem. Res. 20 (1995) 461–465. [9] E. Elisabetsky, L.F. Silva Brum, Linalool as active component of traditional remedies: anticonvulsant properties and mechanisms of action, Curare 26 (3) (2003) 45–52. [10] E. Elisabetsky, L.F. Silva Brum, D.O. Souza, Anticonvulsant properties of linalool on glutamate related seizure model, Phytomedicine 6 (1999) 113–119. [11] J. Ferreira, A.R.S. Santos, J.B. Calixto, A hole for a systemic, spinal and supraspinal l-arginine–nitric oxide–cGMP pathway in thermal hyperalgesia caused by intrathecal injection of glutamate in mice, Neuropharmacology 38 (1999) 835–842. [12] M.E. Fundytus, Glutamate receptors and nociception: implications for the drug treatment of pain, CNS Drugs 15 (2001) 29–58. [13] J.L. Hylden, G.L. Wilcox, Intrathecal morphine in mice: a new technique, Eur. J. Pharmacol. 67 (1980) 313–316.
P.A. Batista et al. / Neuroscience Letters 440 (2008) 299–303 [14] H. Liu, P.W. Mantyh, A.I. Basbaum, NMDA-receptor regulation of substance P release from primary afferent nociceptors, Nature 386 (1997) 721–724. [15] K. Lufty, S.X. Cai, R.M. Woodward, E. Weber, Antinociceptive effects of NMDA and non-NMDA receptor antagonists in the tail flick test in mice, Pain 70 (1997) 31–40. [16] J.C.G. Marvizon, G. Martinez, E.F. Grady, N.W. Bunnett, E.A. Mayer, Neurokinin 1 receptor internalization in spinal cord slices induced by dorsal root stimulation is mediated by NMDA receptors, J. Neurosci. 17 (1997) 8129–8136. [17] M.J. Millan, The induction of pain: an integrative review, Prog. Neurobiol. 57 (1999) 1–164. [18] N. Mjellem-Joly, A. Lund, O.G. Berge, K. Hole, Intrathecal co-administration of substance P and NMDA augments nociceptive responses in the formalin test, Pain 51 (1992) 195–198. [19] V. Neugebauer, Metabotropic glutamate receptors—important modulators of nociception and pain behavior, Pain 98 (2002) 1–8. [20] S. Ozawa, H. Kamiya, K. Tsuzuki, Glutamate receptors in mammalian central nervous system, Prog. Neurobiol. 54 (1998) 581–618. [21] A.T. Peana, P.S. D’Aquila, M.L. Chessa, M.D.L. Moretti, G. Serra, P. Pippia, (−)Linalool produces antinociception in two experimental models of pain, Eur. J. Pharmacol. 460 (2003) 37–41. [22] A.T. Peana, M.G. De Montis, S. Sechi, G. Sircana, P.S. D’Aquila, P. Pippia, Effects of (−)-linalool in the acute hyperalgesia induced by carrageenan, l-glutamate and prostaglandin E2, Eur. J. Pharmacol. 497 (2004) 279–284. [23] A.T. Peana, P. Rubattu, G.G. Piga, S. Fumagalli, G. Boatto, P. Pippia, M.G. De Montis, Involvement of adenosine A1 and A2A receptors in (−)-linalool-induced antinociception, Life Sci. 78 (2005) 2471–2474. [24] A.T. Peana, S. Marzocco, A. Popolo, A. Pinto, (−)-Linalool inhibits in vitro NO formation: probable involvement in the antinociceptive activity of this monoterpene compound, Life Sci. 78 (2006) 719–723.
303
[25] K.I. Rusin, M.C. Jiang, R. Cerne, M. Randic, Interactions between excitatory amino acids and tachykinins in the rat spinal dorsal horn, Brain Res. Bull. 30 (1993) 329–338. [26] T. Sakurada, A. Sugiyama, C. Sakurada, K. Tanno, S. Sakurada, K. Kisara, A. Hara, Y. Abiko, Involvement of nitric oxide in spinally mediated capsaicin- and glutamate-induced behavioural responses in the mouse, Neurochem. Int. 29 (1996) 271–278. [27] A.R.S. Santos, V.M. Gadotti, G.L. Oliveira, D. Tibola, A.F. Paszcuk, A. Neto, H.M. Spindola, M.M. Sousa, A.L.S. Rodrigues, J.B. Calixto, Mechanisms involved in the antinociception caused by agmatine in mice, Neuropharmacology 48 (2005) 1021–1034. [28] A.R.S. Santos, O.G. Miguel, R.A. Yunes, J.B. Calixto, Antinociceptive properties of the new alkaloid, cis-8,10-di-N-propyllobelidiol hydrochloride dihydrate isolated from Siphocampylus verticillatus: evidence for the mechanism of action, J. Pharmacol. Exp. Ther. 289 (1999) 417–426. [29] C. Scheidt, A.R.S. Santos, L. Ferreira, A. Malheiros, V. Cechinel-filho, R.A. Yunes, J.B. Calixto, Evidence for the involvement of glutamatergic receptors in the antinociception caused in mice by the sesquiterpene drimanial, Neuropharmacology 43 (2002) 340–347. [30] L.F. Silva Brum, E. Elisabetsky, D. Souza, Anticonvulsivant properties of linalool in glutamate-related seizure models, Phytomedicine 6 (2001) 107–113. [31] L.F. Silva Brum, T. Emanuelli, D.O. Souza, E. Elisabetsky, Effects of linalool on glutamate release and uptake in mouse cortical synaptosomes, Neurochem. Res. 26 (2001) 191–194. [32] K. Wiech, R.T. Kiefer, S. Topfner, H. Preissl, C. Braun, K. Unertl, H. Flor, N. Birbaumer, A placebo-controlled randomized crossover trial of the N-methyld-aspartic acid receptor antagonist, memantine, in patients with chronic phantom limb pain, Anesth. Analg. 98 (2004) 408–413. [33] M. Zimmermann, Ethical guidelines for investigations of experimental pain in conscious animals, Pain 16 (1983) 109–110.
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Neuroscience Letters journal homepage: www.elsevier.com/locate/neulet
Evidence for the involvement of ionotropic glutamatergic receptors on the antinociceptive effect of (−)-linalool in mice Patr´ıcia Aparecida Batista a , Maria Fernanda de Paula Werner a , Erica Carvalho Oliveira b , Leonel Burgos c , Patricia Pereira c , Lucimar Filot da Silva Brum c , Adair Roberto Soares dos Santos b,∗ a b c
Department of Pharmacology, Center of Biological Science, Federal University of Santa Catarina, Florianopolis, SC, Brazil Department of Physiological Sciences, Center of Biological Sciences, Federal University of Santa Catarina, Florianopolis, SC, Brazil Postgraduate Programme in Genetics and Applied Toxicology, Lutheran University of Brazil, Porto Alegre, RS, Brazil
a r t i c l e
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Article history: Received 9 April 2008 Received in revised form 14 May 2008 Accepted 26 May 2008 Keywords: (−)-Linalool Glutamate Nociception Substance P NMDA receptor
a b s t r a c t (−)-Linalool is a monoterpene alcohol which is present in the essential oils of several aromatic plants. Recent studies suggest that (−)-linalool has anti-inflammatory, antihyperalgesic and antinociceptive properties in different animal models. The present study investigated the contribution of glutamatergic system in the antinociception elicited by (−)-linalool in mice. Nociceptive response was characterized by the time that the animal spent licking the injected hind paw or biting the target organ following glutamate receptor agonist injections. (−)-Linalool administered by intraperitoneal (i.p., 10–200 mg/kg), oral (p.o., 5–100 mg/kg) or intrathecal (i.t., 0.1–3 g/site) routes dose-dependently inhibited glutamate-induced nociception (20 mol/paw, pH 7.4) with ID50 values of 139.1 mg/kg; 34.6 mg/kg; and 0.9 g/site, with inhibitions of 70 ± 4; 72 ± 7 and 74 ± 8%, respectively. However, the intraplantar injection of (−)-linalool partially (49 ± 9%) inhibited glutamate-induced nociception. Furthermore, (−)-linalool (200 mg/kg) given i.p. also reduced significantly the biting response caused by intrathecal injection of glutamate (30 g/site), AMPA (25 ng/site), SP (135 ng/site), NMDA (25 ng/site) and kainate (23.5 ng/site), with inhibitions of 89 ± 6%, 73 ± 11%, 85 ± 4%, 98 ± 2% and 52 ± 15%, respectively. However, (−)-linalool did not inhibit nociception induced by intrathecal injection of trans-ACPD (8.6 g/site). Taken together, these results provide experimental evidences indicating that (−)-linalool produce marked antinociception against glutamate induced pain in mice, possible due mechanisms operated by ionotropic glutamate receptors, namely AMPA, NMDA and kainate. © 2008 Elsevier Ireland Ltd. All rights reserved.
Many plant-derived substances are attractive sources for developing new analgesic agents. Among these natural products, (−)-linalool (Fig. 1) is one natural occurring enantiomer monoterpene compound prevalent in essential oils of various aromatic plant species. Interestingly, experimental studies reported that (−)-linalool exhibit a variety of pharmacological effects, including anticonvulsant, anxiolytic, anti-inflammatory and antinociceptive effects [9,10,23]. In rats, some studies have shown that (−)-linalool reduced thermal hyperalgesia evoked by carrageenan, glutamate and PGE2 , as well as carrageenan-induced paw oedema and formalin-induced nociception, suggesting an important anti-inflammatory action for these essential oil [22]. Moreover, (−)-linalool displayed antinociceptive activity in acetic acid-induced visceral pain in mice, effect that involves activation of both opioidergic and cholinergic neu-
∗ Corresponding author. Tel.: +55 48 3721 9352; fax: +55 48 37219672. E-mail addresses: [email protected], [email protected] (A.R.S.d. Santos). 0304-3940/$ – see front matter © 2008 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2008.05.092
rotransmission [21]. More recently, it has been suggested that the antinociceptive effects of (−)-linalool could be related to the inhibition of nitric oxide (NO) synthesis and to adenosine A1 and A2A receptor-operated mechanisms [23,24]. Psychopharmacological studies have also shown that (−)linalool modulates glutamatergic neurotransmission both in vitro and in vivo conditions, possibly through N-methyl-d-aspartate (NMDA) receptor interactions [30,31]. Glutamate and glutamatergic receptors can be located in both central and peripheral nervous systems and are responsible for mediating most of the excitatory neurotransmission. Although there is some evidence demonstrating the antinociceptive action of (−)-linalool, we have not found any study investigating the effect of (−)-linalool on glutamate-induced pain. Glutamate receptors (GluRs) are divided in two major classes, designated ionotropic and metabotropic receptors, and both play an important role in modulating nociceptive processing at both peripheral and spinal levels [12,20]. The ionotropic receptors (iGluRs) are cation-specific ion channels, and are further
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Fig. 1. Molecular structure of monoterpene (−)-linalool.
subdivided into three groups: N-methyl-d-aspartate (NMDA), ␣-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and kainate receptors. On the other hand, metabotropic receptors (mGluRs) are coupled to GTP-binding proteins (G-proteins), which modulate the production of second messengers [20]. There is a large evidence accumulated that substances capable of blocking both iGluR and mGluR exhibit pronounced antinociceptive and analgesic effects in several mammalian species including humans [6,15,19,27,32]. Therefore, it is supposed that substances capable of blocking GluRs may have clinical potential in the management of some painful states. However, the use of those substances as analgesics is hampered due to the unaccepted side effects observed by these drugs [17]. For this reason, it is believed that new drugs that block GluR with reduced side-effects may have potential clinical indications for some painful states. In light of these considerations, the current study aimed to investigate the ability of (−)-linalool to reduce glutamate-induced nociception in mice hind paw. Further, it was characterized the contribution of the spinal iGluRs- and mGluRs-operated mechanisms in the antinociception caused by (−)-linalool on the biting response caused by intrathecal (i.t.) injection of selective glutamate receptor agonists in mice. All experiments were performed on male Swiss mice (25–35 g), housed 20 to a cage under a 12-h light/12-h dark cycle (lights on at 6:00) in a controlled temperature room (22 ± 2 ◦ C) with free access to laboratory chow and tap water. Mice were acclimatized to the laboratory conditions for at least 1 h before testing that was carried on between 9:00 and 17:00 h. All experiments were conducted under the ethical guidelines of the International Association for the Study of Pain [33] and the experimental procedures were previously approved by the Committee on the Ethical Use of Animals of the UFSC, where the study was conducted. Animals were used only once throughout the experiments. The number of animals and intensities of noxious stimuli used were the minimum necessary to demonstrate the consistent effects of drug treatments. The substances used were l-glutamic acid hydrochloride (glutamate), substance P and (−)-linalool (Sigma Chemical Co., St Louis, USA); kainic acid (kainate), (±)-l-aminocylopentanetrans-1,3-dicarboxylic acid (tACPD), ␣-amino-3-hydoxy-5-methyl4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartic acid (NMDA) (Tocris, Cookson Inc., Ellisville, USA). All drugs were dissolved immediately before administration in saline solution (0.9% NaCl). Glutamate was dissolved in isotonic saline solution, which had its pH adjusted to 7.4 by the addition of NaOH and (−)-linalool was dissolved in saline plus Tween 80. The final concentration of Tween 80 did not exceed 10% and did not cause any effects per se. The choice of the doses of each drug was based on literature data [11,26,29] or on preliminary experiments carried out in our laboratory (results not shown). In an attempt to provide more direct evidence concerning the possible interaction of (−)-linalool with the glutamatergic system, we investigated whether (−)-linalool would be able to antagonize glutamate-induced licking in the mouse paw. The procedure used was similar to describe previously [2]. Animals used were individ-
ually adapted into glass funnel. A volume of 20 l of glutamate (20 mol/paw) was injected intraplantarly (i.pl.) in the ventral surface to the right hind paw. The mice were observed individually for 15 min following glutamate injection. The amount of time the animals spent licking or biting the injected paw was measured with a chronometer and was considered as indicative of nociception. Mice were pre-treated with (−)-linalool by intraperitoneal (i.p. 10–200 mg/kg, 30 min beforehand), oral (p.o., 5–100 mg/kg, 60 min beforehand), intrathecal (i.t., 0.1–3 g/site, 15 min beforehand) or intraplantar (10–300 ng/paw, co-administered with glutamate) routes. Control animals received a similar volume of vehicle systemically (i.p. or p.o., 10 ml/kg), centrally (i.t., 5 l/site) or peripherally (20 l/paw, co-administered with glutamate) routes, before glutamate injection. In another set of experiments, the interaction of (−)-linalool with the glutamatergic system was investigated by using both ionotropic and metabotropic agonists of excitatory aminoacids (EAAs) receptors, which were administered by intrathecal (i.t.) route, causing biting behavior in mice [29]. Animals received (−)linalool (200 mg/kg, i.p.) 30 min before i.t. injection of 5 l of drugs. Injections were given to fully conscious mice using the method described by Hylden and Wilcox [13]. Briefly, the animals were restrained manually and a 30-gauge needle, attached to a 50-l microsyringe, was inserted through the skin and between the vertebrae into the subdural space of the L5–L6 spinal segments. The biting behavior was defined as a single head movement directed toward the lumbar and caudal region of spinal cord or hind limbs, resulting in contact of the animal’s snout with the target organ. Intrathecal injections were given over a period of 5 s. The nociceptive response was elicited by glutamate (30 g/site), AMPA (a selective agonist of AMPA-subtype of glutamatergic ionotropic receptors, 25 ng/site), NMDA (a selective agonist of NMDA-subtype of glutamatergic ionotropic receptors, 25 ng/site), kainate (a selective agonist of kainate-subtype of glutamatergic ionotropic receptors, 23.5 ng/site), trans-ACPD (an agonist of metabotropic glutamate receptors, 8.6 g/site) [29] or substance P (a selective NK1 agonists, 135 ng/site) [13]. As control, a group of mice received vehicle (saline) by i.t. route. The amount of time the mice spent biting the target organ was evaluated following local post-injections of one of the following agonists: glutamate 3 min; AMPA 1 min; NMDA 5 min; kainate 4 min; trans-ACPD 15 min [29] or substance P 6 min [13]. To evaluate some non-specific muscle-relaxant or sedative effects of (−)-linalool, mice were submitted to the rota-rod task [28]. The rota-rod apparatus consisted of a bar with a diameter of 2.5 cm, subdivided into four compartments by disks 25 cm in diameter. The bar rotated at a constant speed of 17 revolutions/min. The animals were selected 24 h previously by eliminating those mice which did not remain on the bar for three consecutive periods of 60 s. Animals were treated with (−)-linalool (10–200 mg/kg, i.p. or 0.1–3 g/site, i.t.) or vehicle (10 ml/kg, i.p. or 5 l/i.t.), 30 min (i.p.) and 10 min (i.t.) before the test. The results are expressed as the time in sets for which animals remained on the rota-rod. The cut-off time used was 60 s. The results are presented as mean ± S.E.M., except the ID50 values (i.e., the dose of (−)-linalool necessary to reduce the nociceptive response by 50% relative to the control value), which are reported as geometric means accompanied by their respective 95% confidence limits. The ID50 value was determined by linear regression from individual experiments using linear regression GraphPad software (GraphPad software, San Diego, CA, USA). Comparisons between experimental and control groups were performed by ANOVA followed by Newman–Keuls test when appropriated. P values less than 0.05 (P < 0.05) were considered as indicative of significance.
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Fig. 2. Effect of (−)-linalool administered intraperitoneally (A), orally (B), intraplantarly (C) or intrathecally (D) against licking induced by intraplantar injection of glutamate (20 mol/paw) in mice. Each column represents the mean of six to eight animals and the error bars indicate the S.E.M. Control values (C) indicate the animals injected with saline and the asterisks denote the significance levels *P < 0.05, ***P < 0.001 when compared with control groups values (one-way ANOVA followed by Newmann–Keuls test).
The results in Fig. 2 (A, B and D) show that (−)-linalool given either systemic (i.p. or p.o.) (5–200 mg/kg) or centrally (i.t.) (0.1–3 g/site), caused significant and dose-dependent inhibition of glutamate-induced nociception. The calculated mean ID50 values obtained by i.p., p.o. and i.t. routes were 139.1 mg/kg (107.3–180.4); 34.6 mg/kg (23.3–51.9) and 0.9 g/site (0.2–2.4), with inhibitions of 70 ± 4, 72 ± 7 and 74 ± 8%, respectively. While intraplantar treatment with (−)-linalool (10–300 ng/paw) partially (49 ± 9%) inhibited glutamate-induced nociception (Fig. 1C). Fig. 3 shows that (−)-linalool (200 mg/kg, i.p., 30 min before) also elicited a pronounced inhibition of the biting response induced by glutamate, AMPA, NMDA, kainate and substance P with inhibitions of 89 ± 6%, 73 ± 11%, 98 ± 2%, 52 ± 15% and 85 ± 4%, respectively. However, the same treatment did not prevent the bit-
Fig. 3. Effect of (−)-linalool (200 mg/kg) administered intraperitoneally on the biting response caused by intrathecal injection of glutamate (30 g/site), NMDA (25 ng/site), AMPA (25 ng/site), kainate (23.5 ng/site), trans-ACPD (8.6 g/site) and substance P (SP) (135 ng/site) in mice. Each column represents the means of six to eight animals and the error bars indicate the S.E.M. Asterisks denote the significance levels*P < 0.05; **P < 0.01 and ***P < 0.001 when compared with control group values (one-way ANOVA followed by Newmann–Keuls test).
ing response induced by the metabotropic glutamatergic receptor agonist trans-ACPD (Fig. 3). (−)-Linalool administered by i.p. (10, 50, 100 and 200 mg/kg) or i.t. (0.1, 0.3, 1.0 and 3.0 g/site) routes did not affect the motor performance on the rota-rod task when compared with animals that received vehicle (control group). The means values ± S.E.M. on the rota-rod task were 176.0 ± 4.0, 176.0 ± 2.5, 178.0 ± 2.0, 176.0 ± 2.5 and 180.0 ± 0.0 s for the i.p. treatment groups and control respectively, and 179.3 ± 0.3; 180.0 ± 0.0; 155.3 ± 24.7, 117.0 ± 30.5 and 179.7 ± 0.3 for the i.t. treatment groups and control, respectively. The results presented in the current study clearly demonstrate that (−)-linalool, the natural occurring enantiomer in essential oils, administered by systemic (oral and intraperitoneal), peripheral (intraplantar) or central (intrathecal) routes, produced significant inhibition of the behavioral nociceptive response caused by intraplantar injection of glutamate into the mouse hind paw. Moreover, the antinociceptive effect of (−)-linalool seems to be related with its ability to modulate ionotropic glutamate receptors (iGluR). It is well established that glutamate is involved in transmission of nociceptive signals from peripheral nervous system to the dorsal horn of the spinal cord. Moreover, it has been reported that the glutamate injection elicited marked nociceptive responses, that is mediated by neuropeptides (like SP) releasing from sensory fibers and due to activation of glutamate receptors (i.e. NMDA), that can stimulate the production of a variety of intracellular second messengers, such as NO [4]. In addition, Beirith et al. [2] have found that the nociceptive response induced by glutamate appears to involve peripheral, spinal and supraspinal sites of action and is greatly mediated by both NMDA and non-NMDA receptors. The results of this study extend previous data from other groups regarding (−)-linalool antinociceptive effect [21–23,14]. They clearly show, for the first time, that (−)-linalool, administered by i.p., p.o. and i.t. routes dose-dependently protects the mice from
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glutamate-induced nociception. On the other hand, the intraplantar injection of (−)-linalool also inhibited the nociception caused by glutamate, though not significantly. From these results, we can infer that the antinociception caused by (−)-linalool on the pro-algesic effect of glutamate involves peripheral and spinal sites of action. Interestingly, the oral administration of (−)-linalool was fourfold more potent in preventing the glutamate-induced nociception than the i.p. administration. We do not have an explanation for this; however, probably pharmacokinetics factors can be contributing to these effects. It is generally recognized that oral administration of (−)-linalool produces metabolites such as 8-hydroxy-linalool and 8-carboxy-linalool [5] but it remains to be seen if these metabolites have antinociceptive effect and additive effect towards (−)-linalool activity. On the other hand, intraplantar injection of (−)-linalool caused only partial inhibition on glutamate-induced nociception in mice hind paw. This result may be due the administration of both substances at the same time, which were different to the schedule used by others, administration routes. However, we cannot rule out the participation of peripheral glutamatergic receptors. The highest dose of (−)-linalool (200 mg/kg) administered by subcutaneous route also reduced thermal hyperalgesia induced by intraplantar injection of glutamate in rats [22]. However, there are marked differences in the methods used among this study and ours, mainly related to route of administration, those difficult comparisons. The treatment of mice with glutamate and selective ionotropic and metabotropic agonists of this excitatory aminoacid (EAA) receptors, we have confirmed previous data from the literature showing that intrathecal injection of glutamate, NMDA, AMPA, kainate and trans-ACPD results in pronounced biting responses ([29], for review see [3]). These results, together with studies using selective antagonists for all the subtypes of glutamate receptors, give further support for the view that NMDA, AMPA, kainate and metabotropic glutamatergic receptors play relevant roles in the establishment or maintenance of painful states (for review see [3,7]). The present results may indicate that, at least in part, the antinociceptive action caused by (−)-linalool in glutamate test could be due to an interaction with the glutamatergic system, more specifically via interaction with iGluR. This assertion is supported by the demonstration that (−)-linalool (200 mg/kg) administered i.p., a dose that produced significant effect on glutamate-induced paw licking, significantly attenuated the biting response induced by intrathecal injection of glutamate and NMDA and, to a lesser extent, that induced by AMPA and kainate. In this regard, it is noteworthy that (−)-linalool have an inhibitory effect on glutamate-binding sites in a competitive manner as well as an inhibitory effect on MK801-binding sites in a non-competitive manner to mouse cortex membranes [8]. In addition, it was also reported that (−)-linalool modulates glutamate activation expression in vitro (comparative antagonism of l-[3 H]glutamate binding) and in vivo (delayed subcutaneous N-methyl-d-aspartate (NMDA)-induced convulsions and blockade of intracerebroventricular quinolinic acid-induced convulsions) [30,31]. On the other hand, the lack of effect of (−)-linalool against intrathecal injection of the glutamatergic metabotropic agonist trans-ACPD, at doses which reduce substantially biting caused by iGluRs agonists, seems to exclude the possible contribution of mGluRs-operated mechanisms to this antinociceptive response. The findings showing that (−)-linalool do not possess any marked irritant effect at the doses and administration routes tested are also relevant. In addition, (−)-linalool given by intraperitoneal and intrathecal routes did not modify locomotor activity evaluated by rota-rod test, thus ruling out the influence of a possible sedative effect in the antinociceptive action.
A large body of evidence indicates an interaction of substance P and glutamate at the spinal level. The behaviour indicative of pain, which can be observed after spinal administration of substance P, is potentiated by co-administration of NMDA [18]. In addition, there are reports showing that pre-synaptic NMDA receptors located on the terminals of small-diameter pain fibers facilitate and prolong the transmission of nociceptive messages through the release of substance P and glutamate [14]. Therefore, an important crosstalk between glutamate and SP in pain transmission has been well documented in the literature [1,6,14,16,25]. Here we also demonstrate that (−)-linalool markedly attenuated the biting response induced by intrathecal injection of substance P. Corroborating with such observations we may speculate that (−)-linalool acting at NMDA receptors may reduce the pain behavior produced by substance P. In summary, these findings not only confirm but also greatly extend previous evidence from the literature which demonstrates that (−)-linalool, administered by peripheric, systemic and spinal routes, possess antinociceptive properties in mice. The antinociceptive effect of (−)-linalool involves peripheral and spinal sites of action and seems to be mediated by interaction with ionotropic glutamatergic-dependent mechanisms, via NMDA receptors. Finally, these results strength the notion that (−)-linalool might be used in the future for the management of pain. Acknowledgements This work was supported by grants from Conselho Nacional ´ de Desenvolvimento Cient´ıfico e Tecnologico (CNPq), Programa de ´ Apoio aos Nucleos de Excelˆencia (PRONEX), Fundac¸a˜ o de Apoio ´ a` Pesquisa Cient´ıfica Tecnologica do Estado de Santa Catarina (FAPESC) and Financiadora de Estudos e Projetos [FINEP, Rede Instituto Brasileiro de Neurociˆencia (IBN-Net)], Brazil. M.F.P. Werner is a Post-Doc fellow and P.A. Batista is PhD fellow. They thank CNPq and CAPES by fellowship support. References [1] A.W. Afrah, C.O. Stiller, L. Olgart, E. Brodin, H. Gustafsson, Involvement of spinal N-methyl-d-aspartate receptors in capsaicin-induced in vivo release of substance P in the rat dorsal horn, Neurosci. Lett. 316 (2000) 83–86. [2] A. Beirith, A.R.S. Santos, J.B. Calixto, Mechanisms underlying the nociception and paw oedema caused by injection of glutamate in the mouse paw, Brain Res. 924 (2002) 219–228. [3] D. Bleakman, A. Alt, E.S. Nisenbaum, Glutamate receptors and pain. Review article, Semin. Cell Dev. Biol. 17 (2006) 592–604. [4] S.M. Carlton, S. Zhou, R.E. Coggeshall, Evidence for the interaction of glutamate and NK1 receptors in the periphery, Brain Res. 2 (1998) 229–238. [5] A. Chadha, K.M. Madyastha, Metabolism of geraniol and linalool in the rat and effects on liver and lung microsomal enzymes, Xenobiotica 14 (1984) 365–374. [6] B.A. Chizh, Novel approaches to targeting glutamate receptors for the treatment of chronic pain: review article, Amino Acids 23 (2001) 169–176. [7] T.J. Coderre, I. Van Empel, The utility of excitatory amino acid (EAA) antagonists as analgesic agents. I. Comparison of the antinociceptive activity of various classes of EAA antagonists in mechanical, thermal and chemical nociceptive tests, Pain 59 (1994) 345–352. [8] E. Elisabetsky, J. Marschner, D.O. Souza, Effects of linalool on glutamatergic system in the rat cerebral cortex, Neurochem. Res. 20 (1995) 461–465. [9] E. Elisabetsky, L.F. Silva Brum, Linalool as active component of traditional remedies: anticonvulsant properties and mechanisms of action, Curare 26 (3) (2003) 45–52. [10] E. Elisabetsky, L.F. Silva Brum, D.O. Souza, Anticonvulsant properties of linalool on glutamate related seizure model, Phytomedicine 6 (1999) 113–119. [11] J. Ferreira, A.R.S. Santos, J.B. Calixto, A hole for a systemic, spinal and supraspinal l-arginine–nitric oxide–cGMP pathway in thermal hyperalgesia caused by intrathecal injection of glutamate in mice, Neuropharmacology 38 (1999) 835–842. [12] M.E. Fundytus, Glutamate receptors and nociception: implications for the drug treatment of pain, CNS Drugs 15 (2001) 29–58. [13] J.L. Hylden, G.L. Wilcox, Intrathecal morphine in mice: a new technique, Eur. J. Pharmacol. 67 (1980) 313–316.
P.A. Batista et al. / Neuroscience Letters 440 (2008) 299–303 [14] H. Liu, P.W. Mantyh, A.I. Basbaum, NMDA-receptor regulation of substance P release from primary afferent nociceptors, Nature 386 (1997) 721–724. [15] K. Lufty, S.X. Cai, R.M. Woodward, E. Weber, Antinociceptive effects of NMDA and non-NMDA receptor antagonists in the tail flick test in mice, Pain 70 (1997) 31–40. [16] J.C.G. Marvizon, G. Martinez, E.F. Grady, N.W. Bunnett, E.A. Mayer, Neurokinin 1 receptor internalization in spinal cord slices induced by dorsal root stimulation is mediated by NMDA receptors, J. Neurosci. 17 (1997) 8129–8136. [17] M.J. Millan, The induction of pain: an integrative review, Prog. Neurobiol. 57 (1999) 1–164. [18] N. Mjellem-Joly, A. Lund, O.G. Berge, K. Hole, Intrathecal co-administration of substance P and NMDA augments nociceptive responses in the formalin test, Pain 51 (1992) 195–198. [19] V. Neugebauer, Metabotropic glutamate receptors—important modulators of nociception and pain behavior, Pain 98 (2002) 1–8. [20] S. Ozawa, H. Kamiya, K. Tsuzuki, Glutamate receptors in mammalian central nervous system, Prog. Neurobiol. 54 (1998) 581–618. [21] A.T. Peana, P.S. D’Aquila, M.L. Chessa, M.D.L. Moretti, G. Serra, P. Pippia, (−)Linalool produces antinociception in two experimental models of pain, Eur. J. Pharmacol. 460 (2003) 37–41. [22] A.T. Peana, M.G. De Montis, S. Sechi, G. Sircana, P.S. D’Aquila, P. Pippia, Effects of (−)-linalool in the acute hyperalgesia induced by carrageenan, l-glutamate and prostaglandin E2, Eur. J. Pharmacol. 497 (2004) 279–284. [23] A.T. Peana, P. Rubattu, G.G. Piga, S. Fumagalli, G. Boatto, P. Pippia, M.G. De Montis, Involvement of adenosine A1 and A2A receptors in (−)-linalool-induced antinociception, Life Sci. 78 (2005) 2471–2474. [24] A.T. Peana, S. Marzocco, A. Popolo, A. Pinto, (−)-Linalool inhibits in vitro NO formation: probable involvement in the antinociceptive activity of this monoterpene compound, Life Sci. 78 (2006) 719–723.
303
[25] K.I. Rusin, M.C. Jiang, R. Cerne, M. Randic, Interactions between excitatory amino acids and tachykinins in the rat spinal dorsal horn, Brain Res. Bull. 30 (1993) 329–338. [26] T. Sakurada, A. Sugiyama, C. Sakurada, K. Tanno, S. Sakurada, K. Kisara, A. Hara, Y. Abiko, Involvement of nitric oxide in spinally mediated capsaicin- and glutamate-induced behavioural responses in the mouse, Neurochem. Int. 29 (1996) 271–278. [27] A.R.S. Santos, V.M. Gadotti, G.L. Oliveira, D. Tibola, A.F. Paszcuk, A. Neto, H.M. Spindola, M.M. Sousa, A.L.S. Rodrigues, J.B. Calixto, Mechanisms involved in the antinociception caused by agmatine in mice, Neuropharmacology 48 (2005) 1021–1034. [28] A.R.S. Santos, O.G. Miguel, R.A. Yunes, J.B. Calixto, Antinociceptive properties of the new alkaloid, cis-8,10-di-N-propyllobelidiol hydrochloride dihydrate isolated from Siphocampylus verticillatus: evidence for the mechanism of action, J. Pharmacol. Exp. Ther. 289 (1999) 417–426. [29] C. Scheidt, A.R.S. Santos, L. Ferreira, A. Malheiros, V. Cechinel-filho, R.A. Yunes, J.B. Calixto, Evidence for the involvement of glutamatergic receptors in the antinociception caused in mice by the sesquiterpene drimanial, Neuropharmacology 43 (2002) 340–347. [30] L.F. Silva Brum, E. Elisabetsky, D. Souza, Anticonvulsivant properties of linalool in glutamate-related seizure models, Phytomedicine 6 (2001) 107–113. [31] L.F. Silva Brum, T. Emanuelli, D.O. Souza, E. Elisabetsky, Effects of linalool on glutamate release and uptake in mouse cortical synaptosomes, Neurochem. Res. 26 (2001) 191–194. [32] K. Wiech, R.T. Kiefer, S. Topfner, H. Preissl, C. Braun, K. Unertl, H. Flor, N. Birbaumer, A placebo-controlled randomized crossover trial of the N-methyld-aspartic acid receptor antagonist, memantine, in patients with chronic phantom limb pain, Anesth. Analg. 98 (2004) 408–413. [33] M. Zimmermann, Ethical guidelines for investigations of experimental pain in conscious animals, Pain 16 (1983) 109–110.