Comparison of the effects of ether and restraint stress on the activity of tuberoinfundibular dopaminergic neurons in female and male rats

The purpose of the present study was to characterize the acute inhibitory effects of restraint stress on the activity of tuberoinfundibular dopamine (DA) neurons as estimated by measuring concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence. The time course of the effects of two types of physical restraint (immobilization in the supine position or confinement in an acrylic cylindrical tube) was determined in unanesthetized and diethylether (ether)-exposed female and male rats. The combination of brief (2 min) exposure to ether followed by 10 and 20 min of supine restraint increased concentrations of prolactin in plasma and decreased DOPAC concentrations in median eminence of both female and male rats. Thirty minutes of supine restraint decreased DOPAC concentrations in the median eminence of female rats that were not exposed to ether, and brief exposure to ether enhanced this effect. By contrast, 30 min of supine restraint failed to alter DOPAC concentrations in the median eminence in either unanesthetized or ether-exposed male rats. Tube restraint in the absence of ether failed to alter DOPAC concentrations in the median eminence of either female or male rats; but in female rats preexposed to ether, 30 min of tube restraint decreased DOPAC concentrations in the median eminence. On the other hand, in the absence of physical restraint, 2 min ether exposure caused a transient increase in prolactin secretion and a concurrent decrease of DOPAC concentrations in median eminence of both female and male rats.(ABSTRACT TRUNCATED AT 250 WORDS)