Neuregulins stimulate the functional expression of Ca(2+)-activated K(+) channels in developing chicken parasympathetic neurons

The developmental expression of macroscopic Ca(2+)-activated K(+) currents (I(K[Ca])) in chicken ciliary ganglion (CG) neurons is dependent in part on trophic factors released from preganglionic nerve terminals. Neuregulins are expressed in the preganglionic neurons that innervate the chicken CG and are therefore plausible candidates for this activity. Application of 1 nM β1-neuregulin peptide for 12 hr evokes a large (7- to 10-fold) increase in I(K[Ca]) in embryonic day 9 CG neurons, even in the presence of a translational inhibitor. A similar posttranslational effect is produced by high concentrations (10 nM) of epidermal growth factor and type α transforming growth factor but not by 10 nM α2-neuregulin peptide or by neurotrophins at 40 ng⋅ml(−1). β1-neuregulin treatment for 12 hr also confers Ca(2+) sensitivity onto large-conductance (285 pS) K(+) channels observed in inside–out patches. β-Neuregulins have no effect on voltage-activated Ca(2+) currents of CG neurons. These data support the hypothesis that β-neuregulins mediate the trophic effects of preganglionic nerve terminals on the electrophysiological differentiation of developing CG neurons.