Regulation of single potassium channels by serotonin in the cell bodies of the tail mechanosensory neurons of Aplysia californica.

Sensory neurons in the pleural ganglion of Aplysia mediate the afferent portion of the tail withdrawal reflex. Previous work has shown that in these neurons and in the siphon sensory neurons of Aplysia, serotonin modulates a steady-state non-inactivating potassium current called the S current. Using the technique of patch clamping, we have examined the kinetics of single potassium channels and found that they share the properties of the S potassium channel of the siphon sensory neurons. This channel has an elementary slope conductance of 73 +/- 9.98 pS (mean +/- S.E.M.) and shows Goldman rectification. It is active at the resting potential and does not inactivate with maintained depolarization. Bath application of serotonin in a majority of experiments decreased the functional number of channels in the patch.