Prolactin Response to Immobilization Stress and Hemorrhage: The Effect of Hypothalamic Deafferentations and Posterior Pituitary Denervation

Abstract

The roles of posterior and anterolateral connections to the mediobasal hypothalamus (MBH) as well as innervation of the posterior pituitary in the PRL response to immobilization (IMO) and hemorrhage (HEM) were studied by means of surgical isolation, performed 6-9 days before stress exposure. Male rats bearing indwelling tail artery cannulae subjected to 120-min IMO reached peak PRL secretion in 5-20 min. HEM of 25% elicited a significant rise of PRL levels. A posterior cut in the MBH, performed without damaging the serotonergic fibers from the brain stem, attenuated the PRL response to 25% HEM, whereas the PRL elevation due to IMO remained unaffected. An anterolateral cut around the MBH eliminated both the IMO- and HEM-induced stimulation of PRL. Posterior lobe denervation reduced by about 27% the PRL response to IMO and eliminated the response to HEM. These results suggest the following conclusions. The neural structures located posteriorly to the MBH are involved in the transfer of signals triggering PRL secretion due to hypovolemia. Intact anterolateral pathways to the MBH and stalk-median eminence region are essential for the PRL-releasing activity under both stimuli. The posterior lobe may be an important link in the PRL stress response in male rats.

Estradiol potentiates hypothalamic vasopressin and oxytocin neuron activation and hormonal secretion induced by hypovolemic shock

“…Furthermore, PRL, a stress-related hormone in rodents, was increased by hemorrhage in the present study. This evidence also supports the hypothesis that the observed increase in OT secretion following hemorrhage could be a nonspecific stress response rather than an effect induced by hypotension or decreased circulating volume (30). Our study also showed that estrogen induces a further increase in OT magnocellular neuronal activation and OT and PRL secretion in response to hemorrhage, which corroborates previous findings showing that estrogen can potentiate some effects demonstrated by stress models (39).…”

Analysis of Pituitary Prolactin and Adrenocortical Response to Ether, Formalin or Restraint in Lactating Rats: Rise in Corticosterone, but No Increase in Plasma Prolactin Levels after Exposure to Stress

“…While the latter groups show an elevation of plasma PRL levels when exposed to stress [1][2][3][4][5][6][7][8][9][10][11], our findings indicate that lactating mothers, either continual ly suckled or isolated for 4 h never exhibit a similar response -plasma PRL of these animals never increases in response to the three kinds of stresses tested. In rats permanently together with their pups, both ether and for malin induced a significant depression in blood PRL con centrations.…”

The effect of genetic variability (degree of homozygosity) on serum levels of the anterior pituitary hormones prolactin, corticotropin, and growth hormone in rats

“…Low serum hormone concentrations in rats of high homozygosity suggest that the capacities of the pituitary gland cells responsible for hormone production decreased as the inbreeding coefficient increased. The release of PRL, ACTH, and GH from the anterior pituitary in various circumstances is controlled by multiple stimulatory and inhibitory factors (Jurcovicova et al, 1990;Vale, 1985, 1987;Yelvington et al, 1984;Ganong, 1980;Moore and Demarest, 1987). High homozygosity, according to our previous examination Zdrojewicz, 1989a, 1991c), often leads to disturbance of metabolism through changes in the relationship of natural activators and inhibitors in many physiological processes.…”