BETA-ENDORPHIN-IMMUNOREACTIVE NEURONS IN THE HYPOTHALAMUS AND MEDULLA OF THE RAT-BRAIN - EFFECT OF PRENATAL ETHANOL

The number and distribution of β-endorphin neurons in the hypothalamus and medulla of rats is compared among three experimental treatment groups: prenatally ethanol-exposed rats, pair-fed control rats, and normally fed control rats. Quantitative analysis of β-endorphin-immunoreactive neurons in 12 sections through the rostral-caudal extent of the mediobasal hypothalamus revealed no significant difference in the total number or distribution of β-endorphin neurons among any of the three treatment groups. The mean number of β-endorphin neurons was consistently less in each of the 12 sections of pair-fed rats compared to normally fed rats, but there was no consistent difference between the mean number of neurons/section in prenatally ethanol-exposed rats compared to the normally fed controls. The distribution and time of appearance of a second population of β-en-dorphin neurons was analyzed in the caudal medulla. β-endorphin-immunoreactive neurons were easily visualized in the caudal medulla of rats from each treatment group on Postnatal Days 9-11. However, this population could not be identified with antisera against β-endorphin on Postnatal Days 19-21 in any treatment group, even though neurons in the hypothalamus of the same rats were easily visualized histochemically at this age. These data suggest that the well-characterized prenatally ethanol-induced alterations in central opioid systems cannot be attributed to changes in the number, distribution, or time of appearance of β-endorphin neurons in the brain. © 1992.