Alpha-adrenoceptor number and function in rat cortex after ethanol and immobilization stress.

Alpha-Adrenoceptor number and function were assessed in rat cortex after ethanol and immobilization stress. Rats subjected to immobilization stress for 2 h/day/7 days showed a significant reduction in alpha 2-adrenoceptors in cortex ( [3H]clonidine binding) but no change in alpha 1-adrenoceptors ( [3H]prazosin binding). The inhibitory effect of clonidine (500 nM) on 3H efflux from cortical slices preincubated with [3H]norepinephrine was reversed in the stressed animals. These effects on alpha 2-adrenoceptor number and function were reduced when stress was accompanied by chronic administration of ethanol (35% of calories in a liquid diet) although when given alone ethanol produced small changes in the same direction as those produced by stress. It is suggested that, in its effects on cortical alpha-adrenoceptors, chronic ethanol administration attenuates the effects of severe stress though itself perhaps acting as a mild stressor when given as part of a liquid diet regimen.