EFFECTS OF SOMATOSTATIN ON POTASSIUM CURRENTS IN BULLFROG SYMPATHETIC-GANGLION NEURONS - POSSIBLE ROLE OF RECEPTOR SUBTYPES

The effects of whole somatostatin (wSS; somatostatin-28) and cyclic somatostatin (cSS; somatostatin-14) were examined on patch-clamped bullfrog sympathetic ganglion neurones. In the C-cells, where muscarine produces hyperpolarization, wSS was also inhibitory and activated an inwardly-rectifying K+ current; cSS was ineffective. By contrast, in the B-cells, where muscarine produces excitatory effects, cSS was also excitatory and was more effective than wSS in suppressing a voltage-dependent, non-inactivating K+-current (I(M)). These results are consistent with the idea that excitatory and inhibitory effects of somatostatin-derived peptides may be mediated via different receptor subtypes.