Discontinuous versus Continuous Drinking of Ethanol in Peripubertal Rats: Effect on 24-Hour Pattern of Hypophyseal-Gonadal Axis Activity and Anterior Pituitary Oxidative Stress

Jan 31, 2012Neuroendocrinology

How Drinking Alcohol in Breaks or Continuously Around Puberty Changes Daily Hormone Patterns and Stress in the Pituitary Gland of Rats

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Abstract

Discontinuous ethanol consumption leads to increased plasma luteinizing hormone (LH) and testosterone levels in peripubertal male rats.

Discontinuous ethanol consumption resulted in disrupted 24-hour rhythmicity of hormone levels.
A significant nocturnal increase in plasma luteinizing hormone (LH), testosterone, and prolactin (PRL) was observed in the discontinuous group.
Plasma ethanol levels were undetectable 24 hours after the last ethanol treatment in the discontinuous group.
Chronic ethanol administration caused increased plasma PRL late in the night and decreased LH and testosterone levels.
Chronic ethanol exposure was associated with a two-fold increase in blood ethanol levels compared to the discontinuous group.
Discontinuously ethanol-treated rats showed decreased expression of certain genes related to nitric oxide synthesis and disrupted diurnal rhythmicity.

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AIMS: Discontinuous (weekend) consumption of alcohol is common in adolescents and young adults. This study therefore assesses, in peripubertal male rats, the effect of discontinuous as compared to chronic feeding of ethanol or control liquid diet.

METHODS: Animals received an ethanol liquid diet (6.2 % w/v) starting on day 35 of life. Every week for 5 weeks, the discontinuous ethanol group received the ethanol diet for 3 consecutive days and the control liquid diet for 4 days. At the 5th week, 24 h after the last ethanol administration to the discontinuously ethanol-treated animals, rats were killed at 4-hour intervals beginning at 09.00 h. Chronically administered rats received the ethanol diet until immediately before study.

RESULTS: Disrupted 24-hour rhythmicity together with a significant nocturnal increase in plasma luteinizing hormone (LH), testosterone and prolactin (PRL) occurred in the discontinuous ethanol group. Plasma ethanol levels were undetectable at 24 h after the last ethanol treatment. In contrast, after chronic ethanol administration, plasma PRL was increased late in scotophase while LH and testosterone decreased; blood ethanol levels were 2-fold greater than those in discontinuously ethanol-administered rats killed immediately after ethanol withdrawal. Circulating testosterone positively correlated with LH levels in control rats only. Chronic administration of ethanol significantly augmented mean expression of pituitary nitric oxide synthase (NOS)-2, heme oxygenase (HO)-1, Per1 and Per2 genes and disrupted their diurnal rhythmicity. Decreased NOS-1 and NOS-2 expression during scotophase, together with suppression of the rhythm in Per1 and Per2 expression, were found in the discontinuous ethanol group.

CONCLUSIONS: Abstinence after discontinuous drinking of alcohol in rats, as compared to chronic administration of ethanol, is accompanied by increases of plasma LH and testosterone, a greater PRL response and a less pronounced oxidative damage of the anterior pituitary.

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Discontinuous versus Continuous Drinking of Ethanol in Peripubertal Rats: Effect on 24-Hour Pattern of Hypophyseal-Gonadal Axis Activity and Anterior Pituitary Oxidative Stress

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