ALTERATIONS IN NEURONAL DEVELOPMENT IN THE SUBSTANTIA-NIGRA PARS COMPACTA FOLLOWING INUTERO ETHANOL EXPOSURE - IMMUNOHISTOCHEMICAL AND GOLGI STUDIES

The effects of gestational ethanol exposure on the development of dopaminergic neurons of substantia nigra pars compacta were investigated in the rat. Pregnant rats were either fed an ethanol-containing liquid diet (6.7% v/v) or pair-fed an isocaloric diet throughout gestation. The morphology of neurons in both ethanol-exposed and pair-fed control offspring was assessed on postnatal day 15 by using tyrosine hydroxylase immunohistochemistry and Golgi impregnation methods. Alterations in the development of neurons were indicated in ethanol-exposed offspring compared with control offspring by the following: (i) tyrosine hydroxylase-positive cell bodies were smaller and appeared more closely packed; (ii) the numbers of second-, third- and fourth-order dendrites and total dendritic segments per cell were reduced; (iii) the dendritic branching pattern relative to distance from the soma was altered; and (iv) some dysmorphic neurons with irregular cell body contours and spheroidal enlargements in the dendrites were encountered in both tyrosine hydroxylase-immunostained and Golgi-stained specimens. The results of the present study suggest that gestational ethanol exposure causes retardation in the development of substantia nigra pars compacta neurons, especially in their dendritic growth and branching, and also causes pathological changes in some neurons. The underdevelopment of dendrites could result in altered development of neuronal circuitry which, in turn, could result in abnormal motor function.