Effect of hypothalamic lesions and androgen on plasma LH levels in castrated male gerbils.

Abstract

The effects of hypothalamic lesions, androgen implants and systemically injected androgen on plasma LH levels in castrated male gerbils were studied using a radioimmunoassay to measure LH. Untreated and sham—operated controls were used in all experiments. Testosterone propionate injected sc daily into 30#x2013;day castrates decreased plasma LH 78% within 48 hr, but pituitary LH was unchanged. DC anodal lesions between the ventromedial nucleus and medial mammillary nucleus (VMH#x2014;MM) and in the preoptic area (POA) in 4#x2013;day castrates had no effect on plasma LH. Lesions in the arcuate nucleus (ARH) and median eminence (ME) resulted in plasma LH decreases of 55 and 77%, respectively, within 48 hr. Subcutaneous injections of 500 ¼g testosterone propionate in gerbils with VMH#x2014;MM or POA lesions and in controls produced a marked decrease in plasma LH, but in gerbils with ARH or ME lesions androgen injection significantly slowed the rate of plasma LH decrease previously induced by the lesions. In a...