ELECTROPHYSIOLOGICAL CHARACTERIZATION OF CEREBELLAR NEURONS FROM ADULT RATS EXPOSED TO ETHANOL DURING DEVELOPMENT

The purpose of this study was to investigate the spontaneous activity of mature rat cerebellar neurons that had been exposed to ethanol (ROH ) during postnatal days 4 to 10, which corresponds to the third trimes ter in humans. Newborn Sprague-Dawley rats were implanted with gastric feeding tubes and were artificially reared from postnatal days 4 to 1 0 with two different diets. The experimental group received 4.5 g/kg/d ay of ROH delivered in a milk solution. Controls received similar feed ing with an isocaloric supplement replacing the EtOH. Electrophysiolog ical evaluations were performed after an EtOH-free rearing period. Alt hough lobules IX and X of the cerebellar vermis appeared morphological ly smaller in the animals neonatally exposed to EtOH, compared with co ntrols, extracellular recordings from both Purkinje cells and Golgi in terneurons in adult rats showed no differences in spontaneous activity or firing pattern between the control and EtOH-exposed animals. Simil arly, excitations and inhibitions of Purkinje neuron activity evoked b y parallel pathway stimulation appeared unaffected by the developmenta l EtOH exposure. However, we did observe a significant decrease in the proportion of Purkinje neurons generating complex spike bursts in the group exposed to EtOH neonatally. These data suggest that, although f ewer Purkinje neurons may survive the brain growth spurt if exposed to EtOH during this critical period of development, those that do surviv e appear to function normally. The observed abnormality in complex spi ke production may result from EtOH effects on developing neurons in th e inferior olive that give rise to the climbing fibers that cause this bursting pattern in Purkinje neurons.