The Effect of L-arginine in the Ventral Tegmenta Area on the Improving Effect of Nicotine on Memory

• Main Authors: MS Shahin, M Piri, MR Zarrindast
• Format: Article
• Language: fas
• Published: Qom University of Medical Sciences 2012-08-01
• Series: Majallah-i Dānishgāh-i ̒Ulūm-i Pizishkī-i Qum
• Subjects: ventral tegmental area; morphine; nicotine; nitric oxide.
• Online Access: http://journal.muq.ac.ir/article-1-116-en.html
• ISSN: 1735-7799; 2008-1375

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<0.05 was considered statistically significant.   Results: Post-training injection of morphine (5 and 7.5mg/kg) decreased the memory retrieval. Injection of nicotine or L-arginine before test by itself has no effect on memory retrieval. On the other hand, pre-test administration of morphine (7.5mg/kg), nicotine (0.5 and 1mg/kg), L-arginine or ineffective doses of L-arginine plus non-effective dose of nicotine restored memory impairment induced by post-training injection of morphine.   Conclusion: The finding of the study indicate that nitric oxide system of the ventral tegmental area may play an important role in the improving effect of nicotine on the morphine-induced amnesia.