The effects of lateral hypothalamic-medial forebrain stimulation and somatostatin antiserum on pulsatile growth hormone secretion in freely behaving rats: evidence for a dual regulatory mechanism.
The purpose of this investigation was to examine the role of somatostatin (SRIF) and electrical stimulation of the lateral hypothalamic-medial forebrain bundle (LH-MFB) on dynamics of pulsatile GH secretion in freely behaving, chronically cannulated male rats with implanted brain electrodes. The effects of administration of anti-SRIF serum (AS-SRIF) on pulsatile GH and on TSH and PRL secretion was also studied. The results are: 1) circulating AS-SRIF increases trough levels of GH in freely behaving rats but has no significant effect on the amplitude of GH secretory bursts or mean GH levels; 2) LH-MFB excitation can stimulate GH release if delivered when circulating GH levels are low; 3) LH-MFB stimulation inhibits secretion of GH if given at the time of a spontaneous GH burst; 4) stimulation-induced GH inhibition is prevented by pretreatment with AS-SRIF, suggesting that this response is mediated by endogenous SRIF; and 5) AS-SRIF increases TSH secretion but has no effect on PRL. These results provide evidence to support the hypothesis that pituitary GH secretion is regulated by a combination of excitatory and inhibitory influences, the inhibitory component of which is mediated by SRIF.
D000818:Animals; D000936:Antigen-Antibody Complex; D001522:Behavior, Animal; D001921:Brain / Q000502:physiology*; D004558:Electric Stimulation; D013006:Growth Hormone / Q000276:immunology / Q000378:metabolism*; D007031:Hypothalamus / Q000502:physiology*; D007106:Immune Sera; D007700:Kinetics; D008297:Male; D011388:Prolactin / Q000378:metabolism; D051381:Rats; D012756:Sheep / Q000276:immunology; D013972:Thyrotropin / Q000378:metabolism
D000936:Antigen-Antibody Complex; D007106:Immune Sera; D011388:Prolactin; D013972:Thyrotropin; D013006:Growth Hormone