The influence of selective adeno- and neurointermedio-hypophysectomy upon plasma and brain levels of beta-endorphin and their response to stress in rats.
Selective ablation of the anterior lobe (AL) of the pituitary led to a fall in basal plasma levels of beta-endorphin immunoreactivity (beta-EI) at 3 and 20 weeks post-surgery (p.s.). Further, the stress-evoked rise in circulating levels of beta-EI was abolished. This operation did, however, severely deplete the beta-EI content of the neurointermediate lobe (NIL). Removal of the NIL did not, in contrast, decrease the beta-EI content of the AL but depressed basal plasma levels of beta-EI at 3 weeks p.s. and attenuated, but did not abolish, the increase in these elicited by stress at both 3 and 20 weeks p.s. In rats not possessing a NIL, a secretion of beta-EI into plasma can thus occur. The possibility that NIL pools of beta-EI contribute to circulating levels of beta-EI is discussed. Removal of the AL depressed the beta-EI content of the hypothalamus and periventricular tissue at 3 and 20 weeks p.s. The Met-enkephalin-immunoreactivity (ME-I) content of the hypothalamus was, in contrast, unaffected. These animals still responded to stress at 20 weeks p.s. with a significant fall in hypothalamic levels of beta-EI. Extirpation of the NIL did not, in contrast, change brain levels of either beta-EI or ME-I. The presence of the AL, but not the NIL, is thus essential for the maintenance of usual levels of beta-EI and ME-I in the brain.
D000818:Animals; D001923:Brain Chemistry; D004723:Endorphins / Q000032:analysis* / Q000097:blood; D004744:Enkephalin, Methionine; D004745:Enkephalins / Q000032:analysis; D007016:Hypophysectomy; D008297:Male; D010902:Pituitary Gland / Q000032:analysis / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000502:physiology; D010904:Pituitary Gland, Posterior / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin
D004723:Endorphins; D004745:Enkephalins; D004744:Enkephalin, Methionine; D001615:beta-Endorphin