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 a nd kinetics of acetylcholine-induced currents (I-ACh) in acutely isola ted superior cervical ganglion (SCG) neurons from spontaneously hypert ensive (SHR) rats and Wistar-Kyoto (WKY) rats, to determine if altered postsynaptic transmitter responsiveness underlies the increased sympa thetic nerve activity in SHR rat neurons. Rapidly activating and slowl y inactivating inward currents were recorded in response to rapid appl ication of ACh (5 mu M to 2 mM). Concentration/response relationships for SCG neurons isolated for SHR and WKY rats had dissociation constan ts of 161 mu M and 169 mu M, maximum responses of 26 nS/pF and 24 nS/p F, and Hill coefficients of 1.8 and 1.9, respectively. Activation of t he currents was fitted well by a single exponential function with conc entration-dependent time constants, whereas inactivation was fitted we ll 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 concentr ation tested. The results demonstrate that the postsynaptic effects of ACh are similar between SHR and WKY rat postganglionic neurons and, t herefore, probably do not contribute to the observed differences in ga nglionic transmission between SHR and WKY rat nerves.