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Background and Objectives: Nitric oxide synthesis has been detected in ventral tegmental area, which is a key brain region that seems to mediate behavioral effect of morphine and nicotine. In the present study, the effects of L-arginine, a nitric oxide precursor, in the ventral tegmental area in nicotine’s effect on morphine-induced amnesia has been investigated.Methods: This study was done experimentally on 250 male rats. Rats were anesthetized with intra-peritoneal injection of ketamine hydrochloride, plus xylazine and then placed in a stereotaxic apparatus. Two stainless-steel cannuale were placed in the ventral tegmental area. The behavioral testing was started in inhibitory avoidance task, and the step-through latency for entering into the dark compartment was measured for the assessment of memory retention. One-side analysis of variance (ANOVA) and Tukey test were used to evaluate the statistical significance between experimental groups. A difference of p

Background and Objectives: Cannabinoids produce a wide array of effects on different species and interact with different neurotransmitter systems in the brain. In the present study, the effects of histaminergic and cannabinoidregic systems as well as their interactions on anxiety-related behaviors were examined on mice.Methods: In this study, at first mice were anesthetized with intra-peritoneal injection of ketamine hydrochloride and xylazine. They were then placed in a stereotaxic apparatus. Two stainless-steel cannuale were placed one mm above CA1 regions of the dorsal hippocampus. After that, seventeen groups of animals were tested with hole board apparatus for measuring anxiety behavior. For the statistical analysis, One-way analysis of variance (ANOVA) and Dunnett's test were used.Results: Intra-CA1 injection of WIN55,212-2 (0.1, 0.5µg/mice) did not modify anxiety-related behaviors in mice. But administration of AM251 (25 and 50ng/mice), histamine or ranitidine (5µg/mice) induced anxiogenic-like response. Also, co-administration of WIN55, 212-2 with histaminergic agents, decreased the anxiogenic-like response of histamine, but not that of ranitidine. Co-administration of an ineffective dose of AM251 with histaminergic drugs did not alter the response induced by these drugs. In all the experiments, locomotor activity was not significantly changed. Conclusion: These results showed that there may be a partial interaction between the cannabinoidergic and the histaminergic systems of the dorsal hippocampus on anxiety-like behaviors.

Background and Objectives: Cannabinoids are a class of psychoactive compounds that produce a wide array of effects in a large number of species. In the present study, the effects of bilateral intra-CA1 injections of an α2-adrenergic receptor agents, on WIN55,212-2 state-dependent learning were examined in adult male Wistar rats. Methods: The animals were bilaterally implanted with chronic cannulae in the CA1 regions of the dorsal hippocampus, trained in a step-down type inhibitory avoidance task, and tested 24h after training to measure step-down latency.Results: Post-training intra-CA1 injection of WIN55,212-2 (0.25 and 0.5µg/rat) induced impairment of memory retention. Amnesia produced by post-training WIN55,212-2 (0.5µg/rat) was reversed by pre-test administration of the same dose of WIN55,212-2 that is due to a state-dependent effect. Pre-test intra-CA1 injection of clonidine (0.5 and 0.75µg/rat, intra-CA1) improved post-training WIN55,212-2 (0.5µg/rat, intra-CA1)-induced retrieval impairment, while pre-test intra-CA1 injection of yohimbine (1µg/rat, intra-CA1) 2min before the administration of WIN55,212-2 (0.5µg/rat, intra-CA1) inhibited WIN55,212-2 state-dependent memory. Conclusion: These results suggest that α2-adrenergic receptors of the dorsal hippocampal CA1 regions may play an important role in Win55,212-2-induced amnesia and WIN55,212-2 state-dependent memory.

Background: Opiate-induced addiction is a main social problem in Iran. As treatment of this problem is a health priority among the medical community, studies on this topic are very crucial. The exact mechanism of dependence on opiates and their withdrawal syndrome remain unclear. It seems that dopaminergic system and locus coeruleus (LC) have an important role in the expression of somatic signs during opioids withdrawal. The LC has been shown to contain significant levels of dopamine (DA). In the present study, the effects of different D2 dopaminergic receptor agonist and antagonist administration in the LC on withdrawal sign expression in morphine dependence is investigated in rats. Methods: Adult male Wistar rats, weighing 220–280 g were divided into eight groups (n=8). Two cannulae were stereotaxically implanted bilaterally into the LC of each rat. After a one-week recovery, seven groups were rendered dependent on morphine by subcutaneous injection during a seven-day period. Non-dependent control animals received saline according to the same protocol. Animals received bilateral intra-LC injections of saline (1 μg/site) and quinpirole (0.1, 0.3 and 0.5 μg/site, a D2 agonist) 15 min and sulpiride (5, 15 and 30 μg/site, a D2 antagonist) 30 min prior to naloxone injection about 24 hours after the last dose of morphine or saline according to their respective group. To calculate the total withdrawal score, as an index of withdrawal syndrome, 20 different withdrawal signs were assessed and the scores of the intensity of these withdrawal signs were added. Results: Total withdrawal scores were significantly decreased by quinpirole (0.1µg/site) and sulpiride (15 and 30 µg/site). Conclusion: The D2 dopaminergic system in the LC may be involved in the morphine-induced dependency in rats. Further studies are needed to define the mechanism of this dependency in order to improve methods for the rehabilitation of addicts.