Abstract: Objective The aim was to study the effects and mechanism of 5-HT on the firing rate of subthalamic neurons in normal rats. Methods With in vivo extracellular single unit recordings, the electrophysiological effects of 5-HT and 5-HT1B, 5-HT2C, 5-HT4 and 5-HT1A receptor agonist on subthalamic neurons were studied. Then to observe the expression of four kinds of 5-HT receptor subtypes on subthalamic nucleus neurons, the immunohistochemical staining was used in the present study. Results Electrophysiological studies showed that exogenous 5-HT increased or decreased the discharge frequency of subthalamic nucleus neurons in normal rats (P<0.001). As 5-HT receptor agonists, CP-93129, RO-600175 and ML-10302 significantly increased the firing rate of subthalamic neurons (CP-93129: P<0.01; RO-600175: P<0.01; ML-10302: P<0.001), while 8-OH-DPAT decreased the firing rate (P<0.01). Conclusion 5-HT altered the excitability of subthalamic nucleus neurons in normal rats, resulting in the dual role of raising and lowering the discharge frequency. The activation of 5-HT1B, 5-HT2C and 5-HT4 receptor increased the firing rate of subthalamic nucleus neurons, while when 5-HT1A receptor was activated, the firing rate was decreased.

Key words: subthalamic nucleus, 5-HT, 5-HT receptors, single unit recording