THE EFFECTS OF IN-UTERO ETHANOL ADMINISTRATION ON THE ELECTROPHYSIOLOGICAL ACTIVITY OF RAT NIGROSTRIATAL DOPAMINERGIC-NEURONS

Iontophoresis and single-unit extracellular recording techniques were utilized to study the effects of in utero ethanol administration on ni grostriatal dopaminergic (NSDA) neurons in adult rats. Pregnant Spragu e-Dawley rats consumed an ethanol-containing liquid diet providing 0%, 17.5%, or 35% ethanol-derived calories (EDC) from gestation day 8 unt il parturition. A separate group was fed standard rat chow as an ad li b. diet control. The dose-response curves of intravenously administere d apomorphine on the spontaneous activity of NSDA neurons were shifted to the right in animals exposed to a liquid diet containing 17.5% or 35% EDC compared to 0% EDC or ad lib. control groups. The responsivene ss of NSDA neurons to microiontophoretic application of the D-2 DA rec eptor agonist, quinpirole, was not altered following in utero ethanol exposure. These results suggest that in utero ethanol exposure may pro duce a down-regulation in the function of DA receptors distinct from t he somatodendritic impulse-regulating D-2 autoreceptors. The firing pa ttern of NSDA neurons was also found to be altered after in utero etha nol exposure. There was a dissociation between the firing rate and bur st activity in neurons that displayed burst-firing patterns in animals with in utero ethanol exposure. These observations agree with biochem ical and behavioral studies that in utero ethanol exposure produces a long-lasting effect on the development of electrophysiological and pha rmacological characteristics of midbrain DA systems in adulthood.