Postsynaptic effects of prolactin and estrogen on arcuate neurons in rat hypothalamic slices

The effects of 17 beta-estradiol (E2) and prolactin (PRL) on the excitability of neurons in the arcuate nucleus were examined using hypothalamic slices obtained from ovariectomized rats. Neither E2 nor PRL affected the excitability of neurons having antidromic responses due to median eminence stimulation. On the other hand, E2 and PRL altered the spontaneous activity of unidentified neurons, which were not activated by median eminence stimulation, by 6 and 11%, respectively. Both excitatory and inhibitory responses were recorded, which were not abolished in the low Ca2+/high Mg2+ medium. These results suggest that E2 and PRL can rapidly modulate the excitability of some arcuate, but presumably not tuberoinfundibular, neurons by acting directly on the postsynaptic membrane.