ANG II AT1 receptors induce depolarization and inward current in rat median preoptic neurons in vitro

Abstract

To examine ANG II receptors in rat median preoptic (MnPO) neurons, we used patch-clamp whole cell recordings in a parasagittal brain slice preparation. Lucifer yellow-filled neurons displayed a simple morphology with two to three aspiny dendrites. Bath-applied ANG II (1-2,000 nM for 30 s) induced a response in 37 of 70 cells. In current-clamp recordings, cells displayed a prolonged (10- to 30-min) depolarizing plateau with action potential discharges and an associated reduction in postburst afterhyperpolarization and spike frequency adaptation. In voltage-clamp recordings (holding potential -65 mV), cells displayed tetrodotoxin-resistant inward currents of 7. 6 +/- 1.9 (n = 5), 9.9 +/- 1.9 (n = 9), and 9.2 +/- 2.2 pA (n = 6) at 10, 200, and 2,000 nM, respectively. Responses were blockable by pretreatment with losartan (2 microM; n = 6) but not by PD-123177 (20 microM; n = 3). Net ANG II-induced current revealed a 7.8 +/- 0. 9% reduction in membrane conductance, decreasing but not reversing at hyperpolarized levels. Neurons expressing a strong hyperpolarization-activated, time-independent inward rectification were more likely to respond to ANG II. There was no correlation between the response of a neuron to ANG II and its response to norepinephrine.