The effect of tubero-infundibular dopaminergic neurons on prolactin and alpha-melanocyte stimulating hormone release

The effect of tubero-infundibular dopaminergic neurons (TIDA) on the release of prolactin (PRL) and alpha-melanocyte stimulating hormone (alpha-MSH) was studied in median eminence-lesioned (MEL) male rats (N = 6-28). Plasma PRL and alpha-MSH levels were significantly elevated 2(86.1 ñ 19.8 and 505.1 ñ 19.1 ng/ml), 4(278.7 ñ 15.5 and 487.4 ñ 125.1 ng/ml), 7 (116.2 ñ 16.2 and 495.8 ñ 62.6 ng/ml) and 14 (247.3 ñ 26.1 and 448.4 ñ 63.8 ng/ml) days after MEL when compared to sham-operated control animals (55.5 ñ 13.4 and 56.2 ñ 6.1 ng/ml, repectively). MEL altered plasma PRL and alpha-MSH levels in a diffential manner, with 1.5-to5.0-fold increase in PRL and an 8.0- to 9.0-fold increase in alpha-MSH. The increase of alpha-MSH levels occured abruptly and remained constant from days 2 to 14. These observations indicate that TIDA plays an important role in the pituitary release of PRL and alpha-MSH and provide evidence that the release of the two hormones occurs in a differential manner

Involvement of beta-adrenergic receptors in the differential release of gonadotropins in acutely orchidectomized rats

To determine the diferential release fo gonadotropins in acutely orchidectomized rats, a single injection of the beta-adrenergic blocker Bornaprolol (FM 24) was administered to the animals and plasma FSH levels weredetermined. FM 24 produced low plasma FSH levels only when injected 16 h before starting the blood collection and had no effect on FSH levels at 0,30 and 46 h after its administration. However, it produced low LH plasma levels at 0,16 and 30 h after administration. These findings confirm that pituitary beta-adrenergic receptors are involved in plasma LH release and suggest that they could also be involved in the differential release of FSH/LH