The possible mechanism of action of ethanol on rat thymus

Alcohol is a known suppressant of the immune system and alcoholics frequently have impaired humoral and cell-mediated immunity. The purpose of this study was to investigate the effect of a single dose of ethanol on the thymus and the possible mechanism of its action. Adult female Wistar rats were divided into three groups which were treated with: (a) ethanol (4 g/kg i.p.), (b) naltrexone (5 mg/kg i.p.) and 45 min later with ethanol, (c) naltrexone alone. Untreated rats served as controls. The animals were killed 20 h after administration of alcohol. Thymuses were removed and fixed in Bouin's solution. Paraffin sections were stained with hematoxylin-eosin and analysed using stereological measurements. Our results showed that a single dose of ethanol significantly decreased the volume of the thymus especially affecting the cortex. This effect was blocked by pretreatment with naltrexone. Therefore, it seems that the effect of ethanol on the thymus is mediated by an opioid-dependent mechanism.