[Influence of dopamine D1 receptors of the dorsal hippocampus on the histamine-induced anxiety behavior in mice]

Dopamine receptors and histamine influence anxiety-like behaviors. Furthermore, interaction between histamine and dopaminergic D1 receptors has been demonstrated in the modulation of some behavior. In the present study, we investigated the interaction between histamine and dopaminergic D1 receptors in the dorsal hippocampus in the anxiety behavior. In this experimental study, the elevated plus maze test was used to test anxiety-like behaviors. Mice were anesthetized with intra-peritoneal injection of ketamine hydrochloride, plus xylazine, and two stainless-steel cannuale were placed in the CA1 region of the hippocampus. Two- and one-way analyses of variance [ANOVAs], followed by LSD test, were used for data analysis. All experiments were performed in accordance with the institutional guidelines for animal care and use. Intra-CA1 injection of histamine and D1 dopamine agonist [SKF 38393] and antagonist [SCH23390] induced anxiety. Intra-CA1 injection SKF 38393 or SCH23390 2 min after of effective dose of histamine [10 micro g/mouse] inhibited anxiogenic effects of histamine. It seems that both histamine and dopaminergic D1 receptors play a part in the modulation of anxiety in the dorsal hippocampus of mice, and that they carry a complex interaction between them

[ effect of L-arginine in the ventral tegmenta area on the improving effect of nicotine on memory]

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. 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. 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. 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

[Interaction between dopamine D2 and NMDA receptors in the dorsal hippocampus of rats in the elevated plus-maze test of anxiety]

Different studies have indicated that glutamate and dopamine are involved in producing anxiety. Furthermore, interaction between NMDA and dopamine receptors has been demonstrated in the modulation of some behaviors. In the present study, the role of dopaminergic D2 receptor in producing anxiety-like behavior induced by inhibition of NMDA receptors was investigated in male wistar 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 CA1 region of hippocampus. All animals were allowed to recover for one week before beginning behavioral test. The elevated plus maze test was used to test anxiety-like behaviors. The results of this study showed that intra-CA1 injection of MK801 [2 micro g/rat] induced anxiolytic effects. Intra-CA1 injection sulpiride [0.25, 0.5 and 0.75 micro g/rat] by itself had no effect on anxiety-like behaviors, but administration of the same doses of sulpiride 5 mins before injection of the effective dose of MK801 [2 micro g/rat, intra-CA1] inhibited anxiolytic effects of MK801. The results indicated that CA1 region of hippocampus have an important role in anxiolytic effects of MK801; and anxiolytic effect of NMDA receptors antagonist is at least partly mediated via D2 receptors of the dorsal hippocampus

[Interaction between harmane and nicotinic in the passive avoidance test]

A number of beta-carboline alkaloids such as harmane are naturally present in the human food chain. Furthermore, some plants which contain beta-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 micro g/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 micro g/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