NEUREGULINS STIMULATE THE FUNCTIONAL EXPRESSION OF CA2-ACTIVATED K+ CHANNELS IN DEVELOPING CHICKEN PARASYMPATHETIC NEURONS()

The developmental expression of macroscopic Ca2+-activated K+ currents (I-K[Ca]) in chicken ciliary ganglion (CG) neurons is dependent in pa rt on trophic factors released from preganglionic nerve terminals. Neu regulins are expressed in the preganglionic neurons that innervate the chicken CG and are therefore plausible candidates for this activity. Application of 1 nM beta 1-neuregulin peptide for 12 hr evokes a large (7- to 10-fold) increase in I-K[Ca] in embryonic day 9 CG neurons, ev en in the presence of a translational inhibitor. A similar posttransla tional effect is produced by high concentrations (10 nM) of epidermal growth factor and type alpha transforming growth factor but not by 10 nM alpha 2-neuregulin peptide or by neurotrophins at 40 ng.ml(-1). bet a 1-neuregulin treatment for 12 hr also confers Ca2+ sensitivity onto large-conductance (285 pS) K+ channels observed in inside-out patches. beta-Neuregulins have no effect on voltage-activated Ca2+ currents of CG neurons. These data support the hypothesis that beta-neuregulins m ediate the trophic effects of preganglionic nerve terminals on the ele ctrophysiological differentiation of developing CG neurons.