5-Hydroxytryptamine increases spontaneous activity of subthalamic neurons in the rat.

The effect of 5-hydroxytryptamine on the spontaneous activity of neurons of the subthalamic nucleus was examined by recording the extracellular unitary activity in an in vitro slice preparation. The most frequent response to 5-hydroxytryptamine (84% of 57 neurons tested) was an increase (twofold of basal at 10 microM) of the discharge frequency. The EC50 for the 5-hydroxytryptamine-induced effect was 1.8 +/- 0.5 microM (mean +/- SEM). The response was dose-dependently blocked by the serotoninergic antagonist mianserin and was not prevented by removal of calcium ions from the perfusing buffer. These results indicate that the serotoninergic input to the rat subthalamic nucleus exerts a postsynaptic excitatory action on most neurons of the nucleus.