ABSTRACT
This chapter focuses on the actions of 5-Hydroxytryptamine (5-HT) on single neurons studied using electrophysiological methods to record from neurons in vitro. It deals with receptor subtypes and the electrophysiological consequences of receptor activation. Combined electrophysiological, morphological, and immunohistochemical studies have shown that many S neurons are likely to be motorneurons providing excitatory and inhibitory input to the muscle layers and to interneurons. A significant obstacle to electrophysiological studies of the 5-HT1P receptor on enteric nerves is the lack of selective and potent antagonists of this receptor. 5-HT applied by superfusion causes slow depolarizations or hyperpolarizations of enteric neurons. However when 5-HT is applied either by iontophoresis or pressure ejection from a fine-tipped pipette positioned near the impaled neuron, a fast depolarization often precedes the slow response. Prior to the pharmacological characterization of 5-HT4 receptors, cisapride was shown to increase the amplitude of fEPSPs recorded from myenteric neurons of guinea pig ileum.
