Effects of lateral ventricle injection of 5,7-dihydroxytryptamine on neurons in the medial prefrontal cortex of rats: An electrophysiology study

The medial prefrontal cortex (mPFC) is closely associated with various psychopathologies in humans, and its dysfunction is invariably accompanied by abnormalities in the serotonin (5-hydroxytryptamine, 5-HT) system of the brain. In this study, in-vivo extracellular recording techniques were used to investigate changes in the excitability of pyramidal neurons and interneurons in the rat mPFC following injection of 5,7-dihydroxytryptamine (5,7-DHT) into the bilateral lateral ventricles to damage the serotoninergic neurons. The levels of 5-HT in the mPFC and dorsal raphe nucleus of rats were determined by high-performance liquid chromatography. The results showed that the levels of 5-HT were significantly reduced in the mPFC and dorsal raphe nucleus two weeks after injection of 5,7-DHT into the bilateral lateral ventricles, relative to the normal group. The discharge frequency of pyramidal neurons in the mPFC was markedly increased compared to the normal group, with a significant rise in burst discharge, while the average discharge frequency of interneurons was significantly reduced and tended towards irregular activity. The results of the study indicated that the brain’s 5-HT neurotransmitter system not only directly affects the activity of mPFC pyramidal neurons but also modulates the electrical activity of interneurons, thereby regulating the local microcircuitry within the mPFC and participating in its function.