Does endogenous 5-HT mediate spontaneous rhythmic activity in chemoreceptor clusters of rat carotid body?

Spontaneous voltage fluctuations often occurred during perforated-patch recordings from clustered rat carotid body (CB) chemoreceptors in vitro. This activity sometimes appeared as rhythmic-like spikes, when cluster size exceeded approximately 20 cells. Spike discharge could be augmented or induced by hypoxia or 5-HT (2-10 microM) application, and inhibited by the 5-HT receptor blocker, ketanserin (50-100 microM). Thus, endogenous 5-HT may contribute to spontaneous firing within CB receptor clusters via autocrine/paracrine mechanisms.