GENDER-RELATED DIFFERENCES EXIST IN CORTICAL [H-3] NISOXETINE BINDINGAND ARE NOT AFFECTED BY PRENATAL MORPHINE EXPOSURE

The present study was designed to test the hypothesis that prenatal mo rphine, which differentially affects hypothalamic norepinephrine conte nt and turnover in male and female rats, has sexually dimorphic effect s on the density of hypothalamic norepinephrine uptake sites in adult offspring, The binding characteristics of norepinephrine transporters were examined in the hypothalamus, preoptic area and frontal cortex of adult male and female rats exposed to morphine (5-10 mg/kg, twice dai ly) or saline on gestation days 11-18, There was a gender-related diff erence in the density of norepinephrine uptake sites measured by [H-3] nisoxetine binding in the frontal cortex of saline controls, with cont rol males having significantly fewer binding sites than control female s, Prenatal morphine administration did not reverse or eliminate this difference. Additionally, prenatal morphine exposure had no effects on either the binding capacity or the affinity of norepinephrine uptake sites in the hypothalamus, preoptic area or frontal cortex of adult pr ogeny, Thus, alterations in hypothalamic norepinephrine content and tu rnover following prenatal morphine exposure are not reflected in alter ations in norepinephrine uptake sites, However, recent immunocytochemi cal work in our laboratory correlated reductions in hypothalamic norep inephrine content and turnover rate with reductions in tyrosine hydrox ylase and dopamine-beta-hydroxylase fiber density in the hypothalamus of morphine-exposed female rats, Therefore, the present results may su ggest that compensatory mechanisms increase the density of norepinephr ine uptake sites in hypothalamic terminal fields of morphine-exposed f emales. Copyright (C) 1996 IBRO.