The Role of 5HT3 Receptor Antagonist of the Lateral Hippocampus on Amnesia Induce by Morphine in Mice

Learning and memory processes occur as a result of interaction of neurotransmitter systems in various brain regions, such as hippocampus. The evidences indicated that serotonergic and opioidergic systems involve in behavioral, learning, and memory results. In the present study, we investigated the effect of the serotonergic system (5-HT) of the lateral hippocampus (CA1) on morphine-induced amnesia.
In this experimental study, the animals were bilaterally implanted with cannulas in the CA1 region of the lateral hippocampus. Morphine was injected intraperitoneally and 5-HT3 receptor antagonist (Y-25130) was injected into the CA1 region. The memory was assessed by a single-trial step-down passive avoidance task and tested after training. The step-down latency was used for the assessment of memory retention in adult male NMRI mice. One-way analysis of variance, followed by Tukey test, were used for the analysis of data.
In this study, pre-test injection of morphine (dose, 5mg/kg) and Y-25130 (dose, 1ng/mouse) decreased memory acquisition process in the adult mice. In addition, ineffective dose of Y-25130 (0.01ng/mouse) along with ineffective dose of morphine (5mg/kg) induced amnesia in mice.
The results of this study showed that there is a synergistic effect between 5-HT3 receptor antagonists of hippocampal CA1 region and morphine.