Influence of nicotinic system and nitric oxide on morphine-induced amnesia

Studies have revealed the effect of nitric oxide on different types of memory and learning and also the interaction between the nicotinic system and opioids. In the present study, the effect of pre-test injection of nicotine on morphine state dependent learning and the effect of intra-NA administration of the nitric oxide on nicotine’s effects in morphine state-dependent learning were investigated. This experimental study was performed on 230 Wistar rats. Rats were anesthetized and then placed in a stereotaxic apparatus. Two cannulas were placed 2 mm above nucleus accumbens shell. A one week gap was considered before beginning of behavioral test. Animals were trained in an inhibitory avoidance task. The drugs were injected after training. The step-through latency was considered as the criterion for the assessment of memory. Data was analyzed by one and two-way variance analysis and Tukey's test using SPSS 17. Post-training injection of morphine induced amnesia (p<0.001) and the amnesia restored with pre-test administration of same doses of morphine. Pre-test injection of nicotine had no effect on inhibitory avoidance memory retrieval, but restored the amnesia. Co-administration of ineffective dose of morphine with different doses of nicotine synergically restored morphine amnesia. Pre-test injection of L-arginine that had no effect (p>0.05) prevented the nicotine reversal effect on memory. Nicotinic acetylcholine and nitric oxide system may be involved in morphine state dependent learning. In addition, L-arginine can inhibit the improving effect of nicotine on morphine-induced amnesia.