Single channel properties of the 5-HT3 subtype of serotonin receptor in primary cultures of rodent hippocampus.

Whole cell and outside-out patch clamp recordings were obtained from primary cultures of rat and mouse hippocampal neurons. Serotonin (5-HT) evoked short-latency fast inward currents in about 5% of neurons. These currents reversed near 0 mV, showed inward rectification, and were inhibited by the 5-HT3 receptor antagonists ICS 205-930, ondansetron and tubocurare. 5-HT activated single channel currents in 14 of 24 membrane patches obtained from neurons which showed 5-HT3-activated whole cell currents; mean amplitude of channel openings was 0.95 +/- 0.09 pA at -100 mV. Chord conductances measured at -80 and -160 mV were 8.3 and 10.5 pS, respectively. 5-HT-induced unitary currents were blocked reversibly by tubocurare (1 microM), ICS 205-930 (30 nM) and ondansetron (100 nM). Thus, single-channel properties of 5-HT3 receptors in hippocampal neurons are similar to those present in peripheral neurons and do not exhibit solely the sub-picosiemen conductance characteristic of the neuroblastoma and neuroblastoma-derived cloned 5-HT3 receptor.