Interaction between Harmane and Nicotinic in the Passive Avoidance Test

Introduction & A number of β-carboline alkaloids such as harmane are naturally present in the human food chain. Furthermore, some plants which contain β-carboline have behavioral effects such as hallucination. In the present study, the effect of intra-dorsal hippocampus injection of nicotinic receptor agonist on memory impairment induced by harmane was examined in mice. This study was conducted at Shahid Beheshti University in 2009. Two hundred and forty mice were anesthetized with intra-peritoneal injection of ketamine hydrochloride, plus xylazine which afterwards were placed in a stereotaxic apparatus. Two cannuale were placed in the CA1 regions of the dorsal hippocampus. All animals were allowed to recover for a total week before beginning of the behavioral testing. After that, the animals were trained in a step-down type inhibitory avoidance task and tested 24 hours after training to measure step-down latency as a scale of memory. Pre-training and post-training, intra-peritoneal injection of harmane impairs inhibitory avoidance memory, but pre-testing injection of harmane did not alter memory retrieval. Pre-testing administration of high dose of nicotine (0.5 µg/mice, intra-CA1) decreased memory retrieval. On the other hand, pre-test intra-CA1 injection of ineffective doses of nicotine (0.1 and 2.5 µg/mice) fully reversed harmane induced impairment of memory. The present results indicated that complex interaction exists between nicotinic receptor of dorsal hippocampus and the impairment of inhibitory avoidance memory induced by harmane.