Estrogen Modulation of the α-1-Adrenergic Response of Hypothalamic Neurons

Abstract

Intracellular recordings were made from 106 arcuate and cell-poor zone (ARC-CPZ) neurons in sagittal slices prepared from intact, ovariectomized and ovariectomized plus estradiol-benzoate-treated female guinea pigs, and the effects of norepinephrine (NE), the αi-agonist methoxamine (MX) and the β-agonist isoproterenol were tested. Either bath application or pressure application of 2–100 µM NE reversibly hyperpolarized and inhibited the spontaneous firing of the majority (57%, n = 60) of ARC-CPZ neurons. Isoproterenol also inhibited the majority (75%) of the ARC-CPZ neurons which it was tested on. In addition, 2–100 µM NE depolarized and/or increased the spontaneous activity of 20% (n = 21) of ARC-CPZ neurons, and some of these (n = 8) exhibited bursting activity. Similar doses of MX mimicked the NE excitation (depolarization and/or increased firing) in 48% (n = 14) of the ARC-CPZ neurons tested. Based on the serum levels of 17β-estradiol, the three groups of females were divided into high (>30 pg/ml) and low (1-adrenergic stimulation.