THE VASOPRESSINERGIC INNERVATION OF THE LATERAL SEPTUM OF THE RAT AFTER CHRONIC ALCOHOL-CONSUMPTION AND WITHDRAWAL

We have recently reported that ethanol ingestion induces morphological changes in the vasopressinergic neurons of the supraoptic nucleus and that withdrawal from alcohol partially reverses these alterations. Si nce the production of vasopressin is not restricted to the magnocellul ar neurons of the hypothalamus, we investigated the effects of long-te rm ethanol intake and withdrawal on the lateral septum, an area heavil y innervated by vasopressinergic fibers. Besides, as ethanol leads to a decrease of the plasma levels of testosterone, a hormone which plays a pivotal role in the development and maintenance of the vasopressine rgic innervation of the lateral septum, we included groups of alcohol- fed animals submitted to testosterone replacement both in physiologica l and supraphysiological doses. In ethanol-treated rats there was a ma rked reduction in the number of vasopressin-immunoreactive fibers in t he lateral septum. Following ethanol withdrawal a partial recovery in the number of vasopressin-immunoreactive fibers was observed. In both groups of ethanol + testosterone-treated animals the vasopressinergic innervation was increased when compared to the alcohol-fed group, alth ough a complete reversal was not achieved. Therefore, two mechanisms m ight be regarded as underlying the impoverishment of the vasopressiner gic innervation in the lateral septum after prolonged alcohol consumpt ion: alcohol-induced cell death in the bed nucleus of the stria termin alis, from where these fibers arise, and/or alcohol-induced decrease i n testosterone plasma levels.