Effects of ethanol withdrawal on β-endorphin levels in rat brain and pituitary

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Abstract

Rats which received a liquid diet containing 6.5% (w/v) ethanol for three weeks became tolerant to the hypothermic effect of an acute dose of ethanol. Withdrawal of this diet was followed by loss of the tolerance within 3 days, and by an accompanying pattern of changes in levels of immunoreactive-ir-β-endorphin in several brain regions. An initial decrease in levels on days 1 and 3 of withdrawal was followed by recovery to control levels on days 8 and 15. This pattern was found in the arcuate nucleus, amygdala, septum, periventricular thalamus and pre-optic periventricular hypothalamus (POPH), but was statistically significant only in the POPH. A different pattern of change in ir-β-endorphin levels was found in the pituitary. The anterior lobe showed a significant depletion of ir-β-endorphin levels before alcohol withdrawal, which recovered by day 8 of withdrawal. This depletion was probably not related to the loss of tolerance to ethanol but was a response to a perturbation of the hypothalamic-pituitary axis of hormonal control.

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    Present address: Department of Pharmacology, John Curtin School of Medical Research, Australian National University, Canberra, A.C.T. 2601, Australia.

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