POSTNATAL-DEVELOPMENT OF MESOACCUMBENS DOPAMINE NEURONS IN THE RAT - ELECTROPHYSIOLOGICAL STUDIES

The postnatal development of antidromically identified mesoaccumbens d opamine (MADA) neurons were examined with single-unit electrophysiolog ical techniques. Rats were anesthetized with chloral hydrate. The phys iological characteristics of 1-, 2-, 4- and 5-week-old rat pups were c ompared to adults (7-9-weeks-old). The basal discharge rate, conductio n velocity, antidromic latency and discharge patterns of MADA neurons were not significantly different among the 4- and 5-week-old and adult MADA neurons. MADA neurons from 1- and 2-week-old pups, however, had significantly lower mean basal discharge rates and significantly lower mean conduction velocities than MADA neurons from the older animals ( i.e., 4-weeks old, 5-weeks old and adults). 1- and 2-week-old MADA neu rons were also found to have significantly longer mean antidromic late ncies than MADA neurons from older animals. Significantly fewer 1- and 2-week-old MADA neurons were found to discharge in a bursting pattern when compared to MADA neurons from older animals. These results indic ate that during early postnatal development MADA neurons are spontaneo usly active, but still physiologically immature. The results of the pr esent study are discussed in the context of previous developmental ele ctrophysiological studies of nigrostriatal dopamine neurons.