- Email: [email protected]
Decreasing of experimental postoperative pain and the prevention of acute pain chronisation: new possibilities
Poster C. Experimental-Animal studies
the Na channel in different areas of the central nervous system (CNS); during development was examined by non isotope in situ hybridization cytochemistry utilizing antisense and sense riboprobes against the b2 sequence, during the postnatal development. It’s expression appears to be selective, and developmentally regulated. Here we present the results from the hippocampal formation and the cerebellum. In the hippocampus Nab2 mRNA was expressed in the pyramidal layer of CAI, CA2, CA3, and the grarurlar layer of the dentate gyms initially at p4 and rapidly increased at p10 to reach adult levels. At p10 and p15 the upper layer of the granular cells at the dentate gyms express mRNA for Nab2, meanwhile the deeper cells do not present any staining. From p22 and, subsequently at p35 and in the adult, the expression of Nab2 mRNA concerns all the areas of the bippocampal region C 1, C2, C3 and remains quite the same. At the dentate gyms, it seems that all the round-shaped cells through all the layers, express mRNA for Nab2, in contrast to the staining of only the upper cell layer at the previous developmental ages. In the cerebellum, labelling was initially moderately observed at p4 at the Purkinje cell layer and internal granular cell layer, acquiring from p15 the adult levels. At ~10, all the Purkinje cells were already giving a clear strong signal that was similarly intense and constantly present throughout the adult life. At p10 in the area of the internal granular layer there are several small-shaped round cells, presumably granular cells, that give a signal that increases progressively to adult levels by ~15. In the molecular layer, Nab2 expression was present in some cells by p10 and persisted until the adult life. No detectable hybridization signal was detected in the molecular layer of the cerebellum at p2, and p4. In conclusion, the different timing of appearance and the regional heterogeneity of the Nab2 mRNA expression, here established by in situ hybridization, are consistent with previous similar observations by Northern blot analysis and suggest that Nab2 subunits may have a role in the pattern of electrogenesis during the developmental processes. (Supported by grants to M.K. from the Greek National Scholarship Foundation (IKY), and the Theodor Theohari Cozzika Foundation)
El
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s43
Pharmacological in vivo studies with LY 354740, a selective, group II metabotropk glutamate receptor agonist
A. Klodzinska, E. Chojnacka-Wojcik, A. Pile, A. Pahrcha, B. Kroczka. Institute of Pharmacology, Polish Academy of Sciences, 12 Smetna Street, 31-343 Krak&, Poland The novel compound (+)-2-aminobicyclo[3.1 .O]hexane-2,6dicarboxylic acid (LY 354740) is a potent and selective, group II metabotropic glutamate (mGlu 2/3) receptor agonist. This compound is the first agonist of this class receptors to produce central effects following systemic administration to animals (Monn et al., 1997). The present study examined the functional activity of LY 354740 in several behavioral models after intraperitoneal injection. LY 354740 was found to show an anxiolytic-like effect in behavioral tests commonly used to predict a potential anxiolytic activity (the Vogel conflict drinking test in rats; the four-plate test in mice). In the Vogel test, LY 354740 (0.5 and 1 mglkg) increased the number of punished licks in a statistically significant manner by about 330 and 270%, respectively. LY 354740 given in doses of 0.25 and 2 mg/kg was inactive in that test. In the four-plate test, LY 354740 (4 and 8 mg/kg, but not its lower doses) increased the number of punished crossings in mice. It was also found that LY 354740 (2,4 and 8 mg/kg) significantly decreased the spontaneous locomotor activity in mice, having reduced it by about 32, 40 and 55%, respectively. At the same time, LY 354740 (2-8 mglkg) did not disturb the motor coordination of mice on the rota-rod. In another behavioral model, LY 354740 (0.5,1 and 4 mg/kg) inhibited the naloxone (4 mglkg) - induced vertical jumping by 35, 36 and 68%, respectively, in morphine -- dependent mice. The above data suggest that LY 354740 may be a potential anxietyrelieving drug; moreover, they also seem to indicate that LY 354740 is capable of inhibiting symptoms of drug dependence,
Reference
References Isom, L.L., De Jongh, K.S., Catterall, W.A., 1994. Auxiliary subunits of voltage-gated ion channels. Neuron 12, 1183-l 194. Isom, L.L., Ragsdale, D.S., De Jongh, K.S., Westenbroek, R.E., Reber, B.F.X., Scheuer, T., Catterall, W.A., 1995. Structure and function of the b2 subunit of brain sodium channels, a transmembrane glycoprotein with a CAM motif. Cell 83, 433-442.
Monn, J.A., Valli, M.J., Massey, SM., Wright, R.A., Salhoff, CR., Johnson, B.G., Howe, T., Alt, C.A., Rhodes, G.A., Robey, R.L., Griffey, K.R., Tizzano, J.I?, Kallman, M.J., Helton, D.R., Schoepp, D.D., 1997. Design, synthesis, and pharmacological characterization of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY 354740): a potent selective, and orally active group 2 metabotropic glutamate receptor agonist possessing anticonvulsant and anxiolytic properties. J. Med. Chem. 40, 528-537.
C-l 19
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n
Formation of phosphatidylethanol in alcohol intoxication
Decreasing of experimental postoperative pain and the prevention of acute pain chronisatlon: new possibilities
N.I. Khodjaeva, M.M. Rakhimov, K.T. Almatov, Sh. Sultanov. Second State Medical Institute, Dept. qf Psychiatry, Tashkent, Farobi 2, Uzbekistan
Y.Y. Kobeliatsky,
At present it is considered to be established fact that chronic exposure to ethanol is accompanied by marked rearrangements of the membrane structure due to ethanol effect. The following aims were set: to study the distribution of PE in the organ of experimental animals ingesting ethanol; to investigate a possibility of PE formation when endogenous membrane phospholipase D is involved, to establish if this phospholipid is formed in erythrocytes of patients with chronic alcoholism. The studies were carried out on white male rats with 100-150 g body weight. The rats were divided into 3 groups 30 animals in each: Group 1 served as the control; the animals of Group 2 received ethanol i/p; the rats of Group 3 got ethanol with liquid feed. The analysis of mitochondrial phospholipids from the livers of the rats who got ethanol i/p and with liquid feed demonstrated that a phospholipid component absent in the control group was found in their structure. We identified this phospholipid as PE. That allowed to make a suggestion that in addition to the know ways of its conversion in the organism ethanol was able to be readily incorporated into the phospholipid composition. It is not excluded that such incorporation may occur at the expense of interaction between phospbolipid membranes and ethanol and be catalyzed by endogenous enzymes or enzymic systems. One of such enzymes may be phospholipase D which can catalyze the reaction between ethanol and membrane phospholipids with formation of Peas the result of the substitution of the alkyl group in a polar portion of a phospholipid molecule for ethanol. These reactions have been studied well in the model systems.
Aim of investigation: Analgetic effects of ketamine (non-selective NMDA antagonists) are well-known. On the other hand, two more possibilities of the decreasing effects of excitatory amino acids, (glutamate, aspartate): first, using magnesium sulfatis, second, calcium blockers of different types. Besides, administration of anti-depressants like amtriptyline, imipramine and others, which block not only presynaptic reuptake of monoamine and serotonin but also sodium channels. Thus we can both reduce excitatory mechanisms in central nervous system and activate descending antinociceptive pathway. This study examined the effects of mutual administration of this drug on postoperative pain. Methods: We used new experimental model of incisional (Brennan et al., 1996). All rats were divided into 3 groups. 1 group: ketamine+ operation. 2 group: ketamine+operation+magnesium sulfatis+nifedipine. 3 group: ketamine+operation+magnesium sulfatis+nifedipine+ amitriptyline. For estimation analgetic effectivity of the drugs we used ‘tail flick’ test (segmental level of pain), vocalisation (suprasegmental level of pain), test ‘open field’ (behavioral responses). We examined rats in 2 hours, on the 1, 2, 3, 4, 5, 6 days after operation. All drugs were administered intraperitoneal. Results: We found greatly reducing of the pain in the third group comparatively with the tirst group (P
LA. Iovenko, A.V Kolomoets. Department of Anaesthesiology, State Medical Academy, Dnepropetrovsk, 320083, Ukraine
s44
Poster C. Experimental-Animal
found highly significant changes in the test of ‘open field’ comparatively with 1 and 2 group (P
References Brennan, T.J., Vandermeulen, E.P., Gebhart, G.F., 1996. Characterization of a rat model of incisional pain, Pain 64(3), 493-521. Status of ketamine in anesthesiology, Edited by E.F. Domino, 1990, NPP Books, 583 p. Proceedings of the 8th World Congress on Pain, Edited by TX Jensen, J.A. Turner, Z. Wiesenfeld-Hallin, Progress in pain research and management, Volume 8, 1997. In IASP Press, 965 p.
El
C-122
Effects of repeated administration of diazepam on serotonergic receptors of 1A, 2 and 3 type in the rat brain
Rump S., Jakowicz I. and Kowalczyk M.. Dept. of Pharmacology and Toxicology, Military Institute of Hygiene and Epidemiology, 01-163 Warszawa, Poland The interactions of benzodiazepines (BDZ) and serotonergic (5HT) system have been reported by many authors. It is of interest to study the influence of BDZ on various types of central 5-HT receptors. Method: Experiments have been performed on rats treated daily for 14 days with diazepam (5 mglkg SC). On the Ist, 7th and 14th day after the treatment animals were killed, brains were removed and dissected. Binding reactions were performed for 5-HT,, receptors in hippocampus using [3H]8-OH-DPAT according to the method described previously (Rump and Jakowicz, 1995) for 5-HT, receptors in frontal cortex using [‘H] ketanserin according to the method by Pazos et al. (1985) and for 5-HT, receptors using [3H] GR65630 according to Kilpatrick et al. (1987). Results were- expressed as B,,, (receptor density) and K, (affinitv constant) values for unlabelled 8-OH-DPAT, ketanserin and GR 65630,’ respectively, in control and experimental groups and were calculated according to the program set up by Munson (1987). Results: Repeated administration of diazepam resulted in a decrease of B,,, and K, for 5-HT,, receptors (from 198 to 130 fmol/mg, and from 2.8 to 1.4 nM/L, respectively). Effects on 5-HT, receptors were transient and were expressed in an increase of B,,, and K, only on the 1st day after the treatment (from 160 to 190 fmol/mg and from 0.5 to 0.8 &l/L). Effects on 5-HT, receptors were unsignificant. Conclusion: These results suggest that activation of BDZ receptors affects 5-HT system, especially its subtype 1A receptors, and to a lesser extent its subtype 2 receptors, having no significant influence on subtype 3 receptors.
References Rump, S., Jakowicz, I., 1995. Europ Neuropsychopharmacol Pazos, A. et al., 1985. Europ J Pharmacol 106, 521. Kilpatrick, G.J. et al., 1987. Nature 330, 746. Munson, P.J., 1987. Ligand: Data Analysis and Curve-Fitting Binding Experiments. NIH, Bethesda.
C-123 El
5, 49.
for Ligand
Repeated antidepressant drugs affect dopamine D, receptors in the rat brain
J. Maj, M. Dziedzicka-Wasylewska, R. Rogoi, Z. Rogbi. Znstitute of Pharmacology, Polish Academy of Sciences, 12 Sm@na St., PL 31-343 Krakdw, Poland Our previous studies indicated that antidepressant drugs with different pharmacological profiles, administered repeatedly, increased the locomotor hyperactivity induced by various dopaminomimetics, e.g. by quinpirole. As - according to the recent study - this drug shows high affinity not only for dopamine D,, but also for D, receptors, question
studies
arises whether D, receptors are involved in the increased response to dopaminomimetics, induced by repeated treatment with antidepressants. In the present paper we used imipramine, amitriptyline (both being noradrenaline - and serotonin, uptake inhibitors), citalopram (a selective serotonin uptake inhibitor), trimipramine and mianserin (both being noninhibitors of amine uptake). All antidepressants tested were administered in a dose of 10 mg/kg p.o., twice a day for 14 days, to male Wistar rats; afterwards, (?)-7-OH-DPAT, a dopamine D, receptor agonist, was injected (3 mg/kg s.c.). (I)-7-OH-DPAT was chosen, because nafadotride, a D, receptor antagonist, inhibits the (?)-7-OH-DPAT hyperlocomotion, but does not affect the hyperlocomotion induced by d-amphetamine or quinpirole. The hyperlocomotion induced by (t)-7-OH-DPAT was significantly increased by repeated administration of all the antidepressants studied. Moreover, a receptor autoradiography technique using [‘HI-7-OH-DPAT as a radioligand was applied to assess the effects of repeated treatment (14 days) with antidepressants on dopamine D, receptors in of Calleja’s islands and in the shell of the nucleus accumbens septi, which are brain regions with a highly selective expression of dopamine D, receptors. The results indicate that in both the examined brain regions there takes place an increase in the binding of [3H]-7-OHDPAT following repeated administration of the antidepressants tested. The results obtained in the present study show that antidepressants administered repeatedly enhance the responsiveness of dopamine D, receptors - most likely via an increase in the density of these receptors. It seems that a mechanism similar to that already observed in the case of dopamlne D, receptors is involved in the effect found in the present paper. Therefore it is hypothesized that the increased responsiveness of dopamine D, and D, receptors is involved in the mechanism of action of antidepressant drugs.
C 124 El
SSRI normalizes f3-adrenoceptor down-regulation in rat brain under chronic unpredtctable stress
T. Matsushita, M. Asakura, Y. Sasuga, N. Bodaiji, K. Osada, S. Miyamoto, J. Imafuku, H. Hasegawa, A. Aoba. Department of Neuropsychiatry, St. Marianna University School of Medicine, Z-16-1, Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216 Japan Long-term treatment with tricyclic antidepressants and monoamine oxidase inhibitors, and repeated electroconvulsive treatment are known to cause a B-adrenergic receptor (R) down-regulation in the rat brain. Since long-term treatment with the selective serotonin reuptake inhibitor (SSRI), such as fluoxetine and citalopram has no effect on the Badrenoceptors in the intact rat brain, the B-R down-regulation is not regarded as a common mechanism in all type of antidepressant agents. On the other hand, the B-R down-regulation is also induced by an exposure to acute and chronic predictable stress, implying an adaptation or habituation to stress. However, chronic unpredictable and inescapable (variable) stress (CVS), a model for depression could not yield this receptor change. In this study we found that concurrent treatment with fluoxetine or citalopram caused the B-R down-regulation in the cerebral cortex of rats treated with CVS for 14 days. As previously reported by authors, mianserin and maprotiline decreased B-R after repeated treatment (twice daily) and this decrease in the receptor was only observed 6 hours after the final injection and was rapidly recovered 24 hours later [l]. The period of the B-R down-regulation was lengthened by increasing serotonin (5-HT) availability with concomitant fluoxetine or 5-hydroxyttyptophan treatment, and shortened by p-chrolophenylalanine administration, indicating that an increase in 5-HT availability plays a role in preserving the B-R down-regulation by noradrenergic potentiating agents (Asakura et al., 1987). In depressed patients, an excess activation of the corticotropin releasing hormone (CRH)-noradrenergic systems is thought to be involved in generating anxiety, sympathetic activation and hyperarousal although an appropriate noradrenergic activation might be required for a relief of a part of depressive symptoms. Moreover, a decrease in the 5-HT turnover in depressed patients has been reported. Accordingly, it is proposed that an increase in 5-HT availability by SSRI might contribute to normalize the B-R down-regulation, an adaptive regulatory mechanism to the hyperactivation of CRH-noradrenergic systems under a stressful situation.
Reference Asakura, M. et al,, 1987. Role of serotonin in the regulation of Badrenoceptors by antidepressants, European J. Pharmacol. 14, 95-100.
the Na channel in different areas of the central nervous system (CNS); during development was examined by non isotope in situ hybridization cytochemistry utilizing antisense and sense riboprobes against the b2 sequence, during the postnatal development. It’s expression appears to be selective, and developmentally regulated. Here we present the results from the hippocampal formation and the cerebellum. In the hippocampus Nab2 mRNA was expressed in the pyramidal layer of CAI, CA2, CA3, and the grarurlar layer of the dentate gyms initially at p4 and rapidly increased at p10 to reach adult levels. At p10 and p15 the upper layer of the granular cells at the dentate gyms express mRNA for Nab2, meanwhile the deeper cells do not present any staining. From p22 and, subsequently at p35 and in the adult, the expression of Nab2 mRNA concerns all the areas of the bippocampal region C 1, C2, C3 and remains quite the same. At the dentate gyms, it seems that all the round-shaped cells through all the layers, express mRNA for Nab2, in contrast to the staining of only the upper cell layer at the previous developmental ages. In the cerebellum, labelling was initially moderately observed at p4 at the Purkinje cell layer and internal granular cell layer, acquiring from p15 the adult levels. At ~10, all the Purkinje cells were already giving a clear strong signal that was similarly intense and constantly present throughout the adult life. At p10 in the area of the internal granular layer there are several small-shaped round cells, presumably granular cells, that give a signal that increases progressively to adult levels by ~15. In the molecular layer, Nab2 expression was present in some cells by p10 and persisted until the adult life. No detectable hybridization signal was detected in the molecular layer of the cerebellum at p2, and p4. In conclusion, the different timing of appearance and the regional heterogeneity of the Nab2 mRNA expression, here established by in situ hybridization, are consistent with previous similar observations by Northern blot analysis and suggest that Nab2 subunits may have a role in the pattern of electrogenesis during the developmental processes. (Supported by grants to M.K. from the Greek National Scholarship Foundation (IKY), and the Theodor Theohari Cozzika Foundation)
El
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s43
Pharmacological in vivo studies with LY 354740, a selective, group II metabotropk glutamate receptor agonist
A. Klodzinska, E. Chojnacka-Wojcik, A. Pile, A. Pahrcha, B. Kroczka. Institute of Pharmacology, Polish Academy of Sciences, 12 Smetna Street, 31-343 Krak&, Poland The novel compound (+)-2-aminobicyclo[3.1 .O]hexane-2,6dicarboxylic acid (LY 354740) is a potent and selective, group II metabotropic glutamate (mGlu 2/3) receptor agonist. This compound is the first agonist of this class receptors to produce central effects following systemic administration to animals (Monn et al., 1997). The present study examined the functional activity of LY 354740 in several behavioral models after intraperitoneal injection. LY 354740 was found to show an anxiolytic-like effect in behavioral tests commonly used to predict a potential anxiolytic activity (the Vogel conflict drinking test in rats; the four-plate test in mice). In the Vogel test, LY 354740 (0.5 and 1 mglkg) increased the number of punished licks in a statistically significant manner by about 330 and 270%, respectively. LY 354740 given in doses of 0.25 and 2 mg/kg was inactive in that test. In the four-plate test, LY 354740 (4 and 8 mg/kg, but not its lower doses) increased the number of punished crossings in mice. It was also found that LY 354740 (2,4 and 8 mg/kg) significantly decreased the spontaneous locomotor activity in mice, having reduced it by about 32, 40 and 55%, respectively. At the same time, LY 354740 (2-8 mglkg) did not disturb the motor coordination of mice on the rota-rod. In another behavioral model, LY 354740 (0.5,1 and 4 mg/kg) inhibited the naloxone (4 mglkg) - induced vertical jumping by 35, 36 and 68%, respectively, in morphine -- dependent mice. The above data suggest that LY 354740 may be a potential anxietyrelieving drug; moreover, they also seem to indicate that LY 354740 is capable of inhibiting symptoms of drug dependence,
Reference
References Isom, L.L., De Jongh, K.S., Catterall, W.A., 1994. Auxiliary subunits of voltage-gated ion channels. Neuron 12, 1183-l 194. Isom, L.L., Ragsdale, D.S., De Jongh, K.S., Westenbroek, R.E., Reber, B.F.X., Scheuer, T., Catterall, W.A., 1995. Structure and function of the b2 subunit of brain sodium channels, a transmembrane glycoprotein with a CAM motif. Cell 83, 433-442.
Monn, J.A., Valli, M.J., Massey, SM., Wright, R.A., Salhoff, CR., Johnson, B.G., Howe, T., Alt, C.A., Rhodes, G.A., Robey, R.L., Griffey, K.R., Tizzano, J.I?, Kallman, M.J., Helton, D.R., Schoepp, D.D., 1997. Design, synthesis, and pharmacological characterization of (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY 354740): a potent selective, and orally active group 2 metabotropic glutamate receptor agonist possessing anticonvulsant and anxiolytic properties. J. Med. Chem. 40, 528-537.
C-l 19
C-l 21 El
n
Formation of phosphatidylethanol in alcohol intoxication
Decreasing of experimental postoperative pain and the prevention of acute pain chronisatlon: new possibilities
N.I. Khodjaeva, M.M. Rakhimov, K.T. Almatov, Sh. Sultanov. Second State Medical Institute, Dept. qf Psychiatry, Tashkent, Farobi 2, Uzbekistan
Y.Y. Kobeliatsky,
At present it is considered to be established fact that chronic exposure to ethanol is accompanied by marked rearrangements of the membrane structure due to ethanol effect. The following aims were set: to study the distribution of PE in the organ of experimental animals ingesting ethanol; to investigate a possibility of PE formation when endogenous membrane phospholipase D is involved, to establish if this phospholipid is formed in erythrocytes of patients with chronic alcoholism. The studies were carried out on white male rats with 100-150 g body weight. The rats were divided into 3 groups 30 animals in each: Group 1 served as the control; the animals of Group 2 received ethanol i/p; the rats of Group 3 got ethanol with liquid feed. The analysis of mitochondrial phospholipids from the livers of the rats who got ethanol i/p and with liquid feed demonstrated that a phospholipid component absent in the control group was found in their structure. We identified this phospholipid as PE. That allowed to make a suggestion that in addition to the know ways of its conversion in the organism ethanol was able to be readily incorporated into the phospholipid composition. It is not excluded that such incorporation may occur at the expense of interaction between phospbolipid membranes and ethanol and be catalyzed by endogenous enzymes or enzymic systems. One of such enzymes may be phospholipase D which can catalyze the reaction between ethanol and membrane phospholipids with formation of Peas the result of the substitution of the alkyl group in a polar portion of a phospholipid molecule for ethanol. These reactions have been studied well in the model systems.
Aim of investigation: Analgetic effects of ketamine (non-selective NMDA antagonists) are well-known. On the other hand, two more possibilities of the decreasing effects of excitatory amino acids, (glutamate, aspartate): first, using magnesium sulfatis, second, calcium blockers of different types. Besides, administration of anti-depressants like amtriptyline, imipramine and others, which block not only presynaptic reuptake of monoamine and serotonin but also sodium channels. Thus we can both reduce excitatory mechanisms in central nervous system and activate descending antinociceptive pathway. This study examined the effects of mutual administration of this drug on postoperative pain. Methods: We used new experimental model of incisional (Brennan et al., 1996). All rats were divided into 3 groups. 1 group: ketamine+ operation. 2 group: ketamine+operation+magnesium sulfatis+nifedipine. 3 group: ketamine+operation+magnesium sulfatis+nifedipine+ amitriptyline. For estimation analgetic effectivity of the drugs we used ‘tail flick’ test (segmental level of pain), vocalisation (suprasegmental level of pain), test ‘open field’ (behavioral responses). We examined rats in 2 hours, on the 1, 2, 3, 4, 5, 6 days after operation. All drugs were administered intraperitoneal. Results: We found greatly reducing of the pain in the third group comparatively with the tirst group (P
LA. Iovenko, A.V Kolomoets. Department of Anaesthesiology, State Medical Academy, Dnepropetrovsk, 320083, Ukraine
s44
Poster C. Experimental-Animal
found highly significant changes in the test of ‘open field’ comparatively with 1 and 2 group (P
References Brennan, T.J., Vandermeulen, E.P., Gebhart, G.F., 1996. Characterization of a rat model of incisional pain, Pain 64(3), 493-521. Status of ketamine in anesthesiology, Edited by E.F. Domino, 1990, NPP Books, 583 p. Proceedings of the 8th World Congress on Pain, Edited by TX Jensen, J.A. Turner, Z. Wiesenfeld-Hallin, Progress in pain research and management, Volume 8, 1997. In IASP Press, 965 p.
El
C-122
Effects of repeated administration of diazepam on serotonergic receptors of 1A, 2 and 3 type in the rat brain
Rump S., Jakowicz I. and Kowalczyk M.. Dept. of Pharmacology and Toxicology, Military Institute of Hygiene and Epidemiology, 01-163 Warszawa, Poland The interactions of benzodiazepines (BDZ) and serotonergic (5HT) system have been reported by many authors. It is of interest to study the influence of BDZ on various types of central 5-HT receptors. Method: Experiments have been performed on rats treated daily for 14 days with diazepam (5 mglkg SC). On the Ist, 7th and 14th day after the treatment animals were killed, brains were removed and dissected. Binding reactions were performed for 5-HT,, receptors in hippocampus using [3H]8-OH-DPAT according to the method described previously (Rump and Jakowicz, 1995) for 5-HT, receptors in frontal cortex using [‘H] ketanserin according to the method by Pazos et al. (1985) and for 5-HT, receptors using [3H] GR65630 according to Kilpatrick et al. (1987). Results were- expressed as B,,, (receptor density) and K, (affinitv constant) values for unlabelled 8-OH-DPAT, ketanserin and GR 65630,’ respectively, in control and experimental groups and were calculated according to the program set up by Munson (1987). Results: Repeated administration of diazepam resulted in a decrease of B,,, and K, for 5-HT,, receptors (from 198 to 130 fmol/mg, and from 2.8 to 1.4 nM/L, respectively). Effects on 5-HT, receptors were transient and were expressed in an increase of B,,, and K, only on the 1st day after the treatment (from 160 to 190 fmol/mg and from 0.5 to 0.8 &l/L). Effects on 5-HT, receptors were unsignificant. Conclusion: These results suggest that activation of BDZ receptors affects 5-HT system, especially its subtype 1A receptors, and to a lesser extent its subtype 2 receptors, having no significant influence on subtype 3 receptors.
References Rump, S., Jakowicz, I., 1995. Europ Neuropsychopharmacol Pazos, A. et al., 1985. Europ J Pharmacol 106, 521. Kilpatrick, G.J. et al., 1987. Nature 330, 746. Munson, P.J., 1987. Ligand: Data Analysis and Curve-Fitting Binding Experiments. NIH, Bethesda.
C-123 El
5, 49.
for Ligand
Repeated antidepressant drugs affect dopamine D, receptors in the rat brain
J. Maj, M. Dziedzicka-Wasylewska, R. Rogoi, Z. Rogbi. Znstitute of Pharmacology, Polish Academy of Sciences, 12 Sm@na St., PL 31-343 Krakdw, Poland Our previous studies indicated that antidepressant drugs with different pharmacological profiles, administered repeatedly, increased the locomotor hyperactivity induced by various dopaminomimetics, e.g. by quinpirole. As - according to the recent study - this drug shows high affinity not only for dopamine D,, but also for D, receptors, question
studies
arises whether D, receptors are involved in the increased response to dopaminomimetics, induced by repeated treatment with antidepressants. In the present paper we used imipramine, amitriptyline (both being noradrenaline - and serotonin, uptake inhibitors), citalopram (a selective serotonin uptake inhibitor), trimipramine and mianserin (both being noninhibitors of amine uptake). All antidepressants tested were administered in a dose of 10 mg/kg p.o., twice a day for 14 days, to male Wistar rats; afterwards, (?)-7-OH-DPAT, a dopamine D, receptor agonist, was injected (3 mg/kg s.c.). (I)-7-OH-DPAT was chosen, because nafadotride, a D, receptor antagonist, inhibits the (?)-7-OH-DPAT hyperlocomotion, but does not affect the hyperlocomotion induced by d-amphetamine or quinpirole. The hyperlocomotion induced by (t)-7-OH-DPAT was significantly increased by repeated administration of all the antidepressants studied. Moreover, a receptor autoradiography technique using [‘HI-7-OH-DPAT as a radioligand was applied to assess the effects of repeated treatment (14 days) with antidepressants on dopamine D, receptors in of Calleja’s islands and in the shell of the nucleus accumbens septi, which are brain regions with a highly selective expression of dopamine D, receptors. The results indicate that in both the examined brain regions there takes place an increase in the binding of [3H]-7-OHDPAT following repeated administration of the antidepressants tested. The results obtained in the present study show that antidepressants administered repeatedly enhance the responsiveness of dopamine D, receptors - most likely via an increase in the density of these receptors. It seems that a mechanism similar to that already observed in the case of dopamlne D, receptors is involved in the effect found in the present paper. Therefore it is hypothesized that the increased responsiveness of dopamine D, and D, receptors is involved in the mechanism of action of antidepressant drugs.
C 124 El
SSRI normalizes f3-adrenoceptor down-regulation in rat brain under chronic unpredtctable stress
T. Matsushita, M. Asakura, Y. Sasuga, N. Bodaiji, K. Osada, S. Miyamoto, J. Imafuku, H. Hasegawa, A. Aoba. Department of Neuropsychiatry, St. Marianna University School of Medicine, Z-16-1, Sugao, Miyamae-ku, Kawasaki, Kanagawa, 216 Japan Long-term treatment with tricyclic antidepressants and monoamine oxidase inhibitors, and repeated electroconvulsive treatment are known to cause a B-adrenergic receptor (R) down-regulation in the rat brain. Since long-term treatment with the selective serotonin reuptake inhibitor (SSRI), such as fluoxetine and citalopram has no effect on the Badrenoceptors in the intact rat brain, the B-R down-regulation is not regarded as a common mechanism in all type of antidepressant agents. On the other hand, the B-R down-regulation is also induced by an exposure to acute and chronic predictable stress, implying an adaptation or habituation to stress. However, chronic unpredictable and inescapable (variable) stress (CVS), a model for depression could not yield this receptor change. In this study we found that concurrent treatment with fluoxetine or citalopram caused the B-R down-regulation in the cerebral cortex of rats treated with CVS for 14 days. As previously reported by authors, mianserin and maprotiline decreased B-R after repeated treatment (twice daily) and this decrease in the receptor was only observed 6 hours after the final injection and was rapidly recovered 24 hours later [l]. The period of the B-R down-regulation was lengthened by increasing serotonin (5-HT) availability with concomitant fluoxetine or 5-hydroxyttyptophan treatment, and shortened by p-chrolophenylalanine administration, indicating that an increase in 5-HT availability plays a role in preserving the B-R down-regulation by noradrenergic potentiating agents (Asakura et al., 1987). In depressed patients, an excess activation of the corticotropin releasing hormone (CRH)-noradrenergic systems is thought to be involved in generating anxiety, sympathetic activation and hyperarousal although an appropriate noradrenergic activation might be required for a relief of a part of depressive symptoms. Moreover, a decrease in the 5-HT turnover in depressed patients has been reported. Accordingly, it is proposed that an increase in 5-HT availability by SSRI might contribute to normalize the B-R down-regulation, an adaptive regulatory mechanism to the hyperactivation of CRH-noradrenergic systems under a stressful situation.
Reference Asakura, M. et al,, 1987. Role of serotonin in the regulation of Badrenoceptors by antidepressants, European J. Pharmacol. 14, 95-100.