Miloslav Krsiak

Chronic morphine induces long-lasting changes in acetylcholine release in rat nucleus accumbens core and shell: an in vivo microdialysis study

Abstract Previously, only in vitro studies have shown that chronic administration of morphine provokes long-lasting enhanced activity of accumbal cholinergic neurons, which may contribute to the behavioural sensitization, positive reinforcement and aversive effects associated with enhanced drug-seeking. The present study was aimed at clarifying whether these adaptive changes would also be supported by in vivo microdialysis measurements in freely moving rats, distinguishing between the accumbal substructures shell and core, and observing behavioural changes simultaneously. Acute administration of morphine dose-dependently decreased acetylcholine (ACh) release in the nucleus accumbens (NAc), with 10 mg/kg SC being most effective, 5 mg/kg ineffective. On day 5 of spontaneous abstinence from chronic morphine treatment (10–40 mg/kg morphine dose once daily for 5 days), when withdrawal symptoms were still present, even a lower morphine dose (5 mg/kg) was effective in decreasing ACh release in the NAc. During the later phase of abstinence, when no withdrawal symptoms were detectable, the opposite effect, i.e. an increase of ACh release was found. This later effect may represent a long-lasting neuroadaptive effect of morphine. These adaptive effects seemed to be more prominent in the NAc shell. Concurrent with these changes in ACh release, morphine challenges produced marked behavioural stereotypes, possibly indicating behavioural sensitization.

Suppressing aggressive behavior with analogs of allopregnanolone (epalon)

3alpha-Hydroxy-20-oxo-5alpha-pregnan-21-yl hemisuccinate (8) was produced by partial acylation of 3alpha,21-dihydroxy-5alpha-pregnan-20-one (14). 3alpha-Fluoro-5alpha-pregnan-20-one (9) was prepared by treatment of 3beta-hydroxy-5alpha-pregnan-20-one (11) with DAST and by solvolysis of tosylate 12 with tetrabutylammonium fluoride. A behavioral test on mice was performed using 3alpha-hydroxy-5alpha-pregnan-20-one (1) and compounds 8 and 9. Compound 8 was found to be inactive, while the fluoro derivative 9 selectively reduced aggressive behavior in mice more than the corresponding 3alpha-hydroxy compound 1; locomotion and other behavioral features were not affected.

Selective antiaggressive effect of an alpha-2 adrenoceptor agonist naphthylmedetomidine in mice.

Alpha-2 adrenoceptors (alpha(2)-ARs) are critically involved in regulating neurotransmitter release from sympathetic nerves and neurons and play an important role in the regulation of awareness, arousal and vigilance. In our recent study, dexmedetomidine, a full alpha(2)-AR agonist, produced antiaggressive effects in the social conflict test in mice at doses that were twice smaller than those producing sedation. The aim of this study was to ascertain antiaggressive effect of a novel drug naphthylmedetomidine, with a more selective alpha(2)-AR activity. Behavioral effects of naphthylmedetomidine (150-1200 microg/kg i.p.) were studied in the activity cage and in the social conflict tests in mice. Naphthylmedetomidine dose dependently decreased aggressive behavior during social conflict in aggressive mice with significant reduction already at the lowest doses tested (150 microg/kg), whereas locomotion and social investigation were significantly decreased only after four times bigger dose of naphthylmedetomidine (600 microg/kg) in aggressive mice. Naphthylmedetomidine had no effect on aggression in nonaggressive mice. Naphthylmedetomidine reduced locomotion in the activity cage significantly only at the highest doses tested (600 and 1200 microg/kg), and this effect was only partially reversed by administration of high doses of an alpha-2 antagonist atipamezole (3 and 10 mg/kg). In nonaggressive mice, the difference between the dose reducing dominant social behavior (social investigation) and locomotion (150 and 300 microg/kg, respectively) was smaller than in aggressive mice. In conclusion, naphthylmedetomidine showed a very strong and selective antiaggressive effect in aggressive mice, which was devoid of locomotion-inhibiting/sedative effect. This study suggests that naphthylmedetomidine may have clinical potential as antiaggressive drug.

Influence on analgesic activity and serum levels after meloxicam complexation with beta-cyclodextrin in mice and rats

The aim of the present study was to evaluate and compare the analgesic activity and serum levels of meloxicam (CAS 71125-38-7) after administration of meloxicam associated with beta-cyclodextrin (BCD, CAS 7585-39-9) and unmodified meloxicam. The analgesic activity was measured using the plantar test (rats) and the writhing test (mice). In the plantar test, BCD-meloxicam (3 mg/kg and 10 mg/kg orally) showed higher analgesic activity than corresponding doses of meloxicam alone; in the writhing test BCD-meloxicam (7 mg/kg and 15 mg/kg orally) showed stronger analgesic activity than unmodified meloxicam. Serum levels of meloxicam were significantly higher, at 0.5 h and 1 h after administration of BCD-meloxicam orally than those of unmodified meloxicam (both dosed at 10 mg/kg). The present results suggest that association with beta-cyclodextrin increases the analgesic activity of meloxicam. This may be due to an icreased systemic bioavailability of meloxicam after oral administration of its complex with beta-cyclodextrin.

Behavioral characteristics of two rat strains differing in sensitivity to the cardiotoxic effect of isoprenaline.

Behavioral pattern was studied in two inbred strains of rats which have different responses to stress. These strains were originally developed from a randomly bred Wistar rat colony, according to high or low myocardial cells sensitivity to cardiotoxic effect of isoprenaline. One strain is very sensitive to isoprenaline cardiotoxicity (IS = isoprenaline sensitive) the other strain is more resistant (IR = isoprenaline resistant). In the IR strain the immobilization immersion stress causes high incidence of gastric ulcers, while the IS strain is prone to heart pathology. In this communication we report the differences in behavior of these two rat lines in three tests: open field, intruders test and Porsolts forced swimming test. The IS animals were passive and anxious in open field test, submissive in intruders test and they showed more floating time in Porsolts forced swimming test. The IR rats were active, aggressive and dominant.

230 EXPRESSION AND PRODUCTION OF SPINAL CYCLOOXYGENASE 1 AND CYCLOOXYGENASE 2 IN THE SPARED NERVE INJURY MODEL OF NEUROPATHIC PAIN

with 100mM ATP. Total RNA was isolated using RNeasy Mini kit (Qiagen), reverse transcribed, and quantification was performed by qPCR (TaqMan, Applied Biosystems). The expression of gene modulation produced by ATP was calculated by the ddCt method and normalized to 18S as endogenous control. BDNF production in supernatants from ATP-stimulated cells was quantified using RayBio® Human BDNF ELISA kit (RayBiotech). ATP caused a time-dependent induction of BDNF gene expression in both groups of patients (up to 13 fold for OA and up to 8 fold for RA) and the healthy volunteer (up to 14 fold) as the induction reached its maximum at 2h. Extracellular release of BDNF was also induced and after 2h stimulation was 17.8–22 pg/ml for RA, 19.6–23 pg/ml for OA and 22 pg/ml for healthy control. BDNF is a neurotransmitter involved in nociceptive hypersensitivity in the central nervous system and we could show that its increased expression is a direct effect of ATP in synovial fibroblasts of both OA and RA patients thus BDNF might be a possible therapeutic target for better pain management of arthritic joint pain.

267 THE EFFECT OF PARACETAMOL ON PERIAQUEDUCTAL GRAY RELEASE OF GLYCINE IN THE INFLAMMATORY PAIN

value 1.94±0.74mg/kg indicating a synergistic interaction. The derived theoretical additive ED50 value for the gabapentinmetamizole combination (14.22±9.55mg/kg) was not significantly greater than the observed ED50 (12.67±5.26mg/kg), which corresponds to an additive interaction. The derived theoretical additive ED50 value for the gabapentin-paracetamol combination was 59.95±16.77mg/kg, while the experimental value of this combination was 127.61±56.98mg/kg. These data indicate a subadditivity between the gabapentin and paracetamol. Conclusions: Data suggest that low doses of the diclofenacgabapentin combination can interact synergistically and therefore this drug association may represent a therapeutic advantage for the clinical treatment of ipain. Acknowledgment: Supported by research grant VSMSM0021620816

266 EXAMINATION OF THE INTERACTION BETWEEN GABAPENTIN AND DICLOFENAC, METAMIZOLE OR PARACETAMOL IN THE WRITHING TEST IN MICE

263 LONGITUDINAL NUMBERS-NEEDED-TO-TREAT (NNT) ANALYSES OF ANALGESIC TREATMENTS FOR CHRONIC LOW BACK PAIN TO ACHIEVE VARYING RESPONSE LEVELS AND STABILITY T.J. Schnitzer, R.A. Moore, N.P. Katz, A. Gammaitoni *, A. Mehta, H. Wang, P. Peloso. Physical Medicine and Rehabilitation, Northwestern University Feinberg School of Medicine, Chicago, United States; Pain Research, Nuffield Department of Anaesthetics, Oxford, United Kingdom; Clinical Research, Analgesic Research, Needham, United States; Merck Research Laboratories, Rahway, United States

185 ANALYSIS OF SPINAL COX-1 AND COX-2 MRNA EXPRESSION IN THE MODEL OF MONOIODOACETE-INDUCED OSTEOARTHRITIS

in females than in males (0.05< p< 0.01). Estradiol-treated rats, both males and females, showed significantly less ureteral pain behavior than Testosteroneand Oil-treated rats (p< 0.01). All male stone-implanted rats had significantly higher plasma levels of Estradiol than male sham-stone rats (p< 0.01). Conclusions: The behavioral results suggest a higher sensitivity of the female sex to pain from the urinary tract. Supplementation with Estradiol attenuates this pain in both sexes, suggesting an analgesic role of “pharmacologic doses” of the hormone in acute, recurrent visceral pain.

645 PRECLINICAL TESTING OF BETA-CYCLODEXTRINE MELOXICAM IN EXPERIMENTAL PAIN MODELS

Background and Aims: The aim of this study is the evaluation of adverse events like heamodynamic parameters and hepatic, renal and coagulation disturbances in postoperative analgesia with intravenous paracetamol therapy for 48hours. Methods: Patients who were undergoing laminectomy and not have renal, gastric, hepatic and coagulation disturbances were included in this study. Analgesic management was standardized in all patients during anaesthesia. In group T (n = 15) patient controlled analgesia (PCA) with tramadol, in group T+P (n = 15) the same PCA protocol and 1 gr.100ml−1 paracetamol IV infusion, at every 6 hours for 2 days were administered. Preoperatively, postoperatively and at the end of second day, prothrombin time, activated thromboplastin time, thrombocyte-leucocyte count, urea, kreatinine, aspartate aminotransferase, alanine aminotransferase and blood glucose were measured. Mean blood pressure (MBP), heart rate (HR), visual analog scale (VAS) and adverse effects (allergic reactions, local findings, neuseavomiting, gastric irritation) were recorded. Results: Demographig variables, duration of surgery and initial pain intensity in each group were similar. There were no significant difference in hematological and biochemical parameters between groups. Also there were no significant differences between groups with respect to VAS, HR and MAP in any measurement and we did not observe any local reaction or systemic adverse effect. Conclusion: Intravenous paracetamol is a safe and well tolerable agent as a postoperative analgesic in its long term, ceiling dose (4 g/day, 2 days) use.