INVESTIGATION OF PITUITARY INFLUENCES ON AUTOANALGESIA

(1) The effect of manipulations of pituitary hormonal systems on several paradigms of analgesia, as assessed by the tail-flick procedure, were investigated. (2) Systemic injection of ACTH did not elicit analgesia at 15, 30 or 60 min post injection. (3) Hypophysectomy had no effect upon analgesia elicited by acute foot shock. (4) Analgesia, elicited by classically conditioning fear to the tail-flick procedure, was slightly potentiated by hypophysectomy. (5) Hypophysectomy also potentiated morphine-induced analgesia at 2 and 3 hr, but not at 15, 30 or 60 min post injection. (6) These data suggest that neurochemical events in addition to pituitary-adrenal activation are necessary to elicit autoanalgesia (behaviorally-induced antinociception) and that CNS changes in opioid peptide activity which accompany autoanalgesia are independent of pituitary endorphins. © 1979.