A, the TRH-induced current in the presence of PKC inhibitor chelerythrine. B, the TRH-induced current in the presence of the IP3 receptor-inhibitor 2-APB. C, effect of intracellular Ca2+ chelation by BAPTA on the TRH response. Caffeine responses recorded using perforated patch-clamp recordings (left panel) and conventional whole-cell patch-clamp recordings (right panel). Although the caffeine response was abolished by intracellular dialysis of BAPTA, the TRH response was unaffected. Hyperpolarizing step pulses of 500 ms duration from a VH of −50 mV to −60 mV were applied every 10–15 s. D, summary of the mean TRH-induced currents recorded under the various conditions as indicated. Each column shows the mean ±s.e.m. from 4–8 neurons.