Regulation of pituitary cyclic AMP, plasma prolactin and POMC-derived peptide responses to stressful conditions

Neuroendocrine responses to emotional stress: possible interactions between circulating factors and anterior pituitary hormone release

We have shown that a psychological stressor can elicit increases in plasma AVP levels in normal human subjects. Since AVP can enhance the release of ACTH, and the pituitary gland is outside the blood-brain barrier, AVP present in the general circulation might extend the time course of stress-induced, CRF-mediated release of ACTH from the anterior lobe. Since PRA is involved in the synthesis of angiotensin I, the precursor of AII, and AII is known to enhance CRF-mediated release of ACTH from pituitary cells and to stimulate release of AVP, it is possible that the increase in PRA also contributed to the release of AVP and ACTH in this study. Reports differ as to whether circulating catecholamines can release ACTH in vivo by direct action on the pituitary. Finally, it has been reported that beta-EP enhances the release of PRL, and inhibits release of AVP. Since the increase in beta-EP in the present study was quite robust, it might have extended the PRL release, and truncated the AVP response.

Maze performance: a direct comparison of food vs. water mazes

The purpose of these experiments was to evaluate the utility of a water maze for testing performance in nonfood-restricted rats. Water maze performance was compared to performance in a food-rewarded (food) maze. Separate groups of rats were given single daily trials of 34 days in one of two mazes. The path through each maze was identical; in fact, the same maze was used with the exception that the maze was filled with water during water maze testing and left dry during the food maze testing. In the food maze, a chocolate peanut butter chip was placed at the finish. In the water maze an out-of-the-water platform was placed at the finish. The time to reach the finish was measured for each trial. Both free-feeding and food-restricted rats were tested in each maze. Free-feeding rats learned the food maze with great difficulty, requiring more than 30 trials. Food-restricted rats learned the food maze more quickly than did free-feeding rats. Free-feeding rats learned to solve the water maze more quickly than the food maze. Food-restricted rats also learned the water maze more quickly than the food maze and learned both mazes faster than free-feeding rats. Plasma levels of corticosterone, ACTH and prolactin were measured in all rats immediately following completion of the last maze trial. Plasma corticosterone levels were elevated and plasma prolactin levels were decreased in both food-restricted groups as compared to free-feeding rats, demonstrating that food restriction was chronically stressful.(ABSTRACT TRUNCATED AT 250 WORDS)