ELECTROPHYSIOLOGICAL STUDY OF NUCLEUS GIGANTOCELLULARIS NEURONS IN GUINEA-PIG BRAIN-STEM SLICES

Gigantocellular neurons of the medullary nucleus gigantocellularis rep resent a major source of reticulospinal pathways. Among other roles, t hey have been involved in the processing of vestibular information. Th e aim of the present study was to describe the major intrinsic membran e properties of these cells in guinea-pig brainstem slices. We found n ucleus gigantocellularis neurons to be segregated in two cell types. T ype A nucleus gigantocellularis neurons were characterized by the pres ence of a single large afterhyperpolarization and a potent transient 4 -aminopyridine-sensitive rectification likely due to the presence of a transient outward potassium current. In contrast, type B nucleus giga ntocellularis neurons had a narrower and faster rising action potentia l followed by an early fast and a delayed slower afterhyperpolarizatio n. In contrast to type A neurons, type B neurons were, in addition, en dowed with subthreshold tetrodotoxin-sensitive sodium-dependent platea u potentials. Whereas both cell types were endowed with high-threshold calcium-dependent action potentials, only type B nucleus gigantocellu laris neurons also displayed long-lasting calcium-dependent plateau po tentials. These results show that nucleus gigantocellularis neurons ca n be segregated by their intrinsic membrane properties in two cell typ es which are very similar to those that we have previously described i n the medial vestibular nucleus. The possibility that these difference s between type A and B neurons might play a role in the segregation be tween tonic and kinetic cells is discussed. Copyright (C) 1996 IBRO. P ublished by Elsevier Science Ltd.