Acetylcholine-induced currents in acutely dissociated sympathetic neurons from adult hypertensive and normotensive rats have similar properties.

Whole-cell patch-clamp recordings were used to compare the amplitude and kinetics of acetylcholine-induced currents (IACh) in acutely isolated superior cervical ganglion (SCG) neurons from spontaneously hypertensive (SHR) rats and Wistar-Kyoto (WKY) rats, to determine if altered postsynaptic transmitter responsiveness underlies the increased sympathetic nerve activity in SHR rat neurons. Rapidly activating and slowly inactivating inward currents were recorded in response to rapid application of ACh (5 microM to 2 mM). Concentration/response relationships for SCG neurons isolated for SHR and WKY rats had dissociation constants of 161 microM and 169 microM, maximum responses of 26 nS/pF and 24 nS/pF, and Hill coefficients of 1.8 and 1.9, respectively. Activation of the currents was fitted well by a single exponential function with concentration-dependent time constants, whereas inactivation was fitted well by a double exponential function also with concentration-dependent time constants. The time constants of both activation and inactivation for SHR and WKY rats were not significantly different at any concentration tested. The results demonstrate that the postsynaptic effects of ACh are similar between SHR and WKY rat postganglionic neurons and, therefore, probably do not contribute to the observed differences in ganglionic transmission between SHR and WKY rat nerves.