Whole cell patch recordings from forebrain slices demonstrate angiotensin II inhibits potassium currents in subfornical organ neurons

Whole cell patch clamp recordings have been obtained from SFO neurons in a forebrain slice preparation. Basic electrophysiological characteristics recorded from these cells in current clamp mode showed a mean resting membrane potential of -57.0 +/- 2.5 mV (+/- SEM, n = 7), mean input resistance of 900 +/- 110 M Ohm (n = 7), and a mean spike amplitude of 68.6 +/- 4.1 mV (n = 7), accompanied by either irregular or no spontaneous activity. All cells also demonstrated a delayed return to baseline membrane potential following large hyperpolarizing current pulses indicative of the presence of a rapidly activated transient potassium current in these neurons. Voltage clamp recordings identified both rapid transient, and a sustained outward currents which demonstrated the characteristics of I-A and I-K respectively. While bath administration of angiotensin II (Ang) (10(-7) M) was without effect on I-K in 4 of 4 neurons tested, I-A was reduced by between 20 and 100% in the same 4 neurons. These data provide the first description of the basic electrophysiological characteristics of SFO neurons recorded in forebrain slice preparations. They also provide the first direct evidence suggesting that Ang may exert its control over the excitability of SFO neurons through modulation of I-A in these cells.