ADRENALECTOMY AND DEXAMTHASONE ATTENUATE MILD SHOCK-INDUCED ANALGESIA. M.K. Biles, J.M Barter* and J.W. Grau. Department of Psychology, Texas A&M University, College Station, TX 77843.
Prior work suggests that the opioid analgesia observed in rats after an extended exposure (e.g. 20 min or more) to intermittent shock is "hormonal" in nature because it is blocked by adrenalectomy and dexamethasone. The opioid analgesia observed after less severe shock schedules is thought to be "neural" in nature since it is not affected by manipulations that disrupt the pituitary-adrenal axis (Terman, G.W. et al., Science, 226, 1270, 1984). We have previously shown that exposure to very mild shock (3, 0.75-s, 1.0 mA tail-shocks) can elicit both a transient nonopioid and long-lasting opioid analgesia on the tail-flick test (Grau, J.W., Beh. Neurosci., 101, 272, 1987). It is currently unclear whether the pituitary-adrenal axis plays a role in this analgesia. We addressed this issue by testing the impact of adrenalectomy and dexamethasone (1 mg/kg administered 2 hrs before testing) on mild shock-induced analgesia. We found that both manipulations attenuated, but did not eliminate, the analgesia. The results suggest that the pituitary-adrenal axis also plays a role in the production of mild shock-induced analgesia. Supported by DA-05846-01 to J.W.G.
Published in Society for Neuroscience Abstracts, 16, 1990.