Modulation of catecholamine turnover rate in brain regions of rats exposed prenatally to morphine.

The concentration and turnover rate of brain catecholamines were measured in the hypothalamus, preoptic area (POA), frontal cortex, striatum and cerebellum of adult male and female rats exposed in utero to morphine (5-10 mg/kg/twice a day) during gestation days 11-18. Norepinephrine (NE) and dopamine (DA) turnover rates were estimated following alpha-methylparatyrosine (AMPT) administration. Prenatal morphine altered NE content and turnover in male and female rats in a regionally specific, sexually dimorphic manner. Basal NE content increased approximately 60% in the hypothalamus of male rats, but it decreased about 30% in the hypothalamus of female rats. NE turnover in the hypothalamus of morphine-exposed rats increased 50% in males and decreased 50% in females. Prenatal morphine had no effects on NE turnover in the male POA, but in female rats NE turnover decreased approximately 60%. Alterations in the frontal cortex of morphine-exposed male and female rats resembled the pattern in the hypothalamus; however, the differences did not reach statistical significance. In addition, prenatal morphine had no effect on striatal or cerebellar NE or on basal levels or turnover of DA in any brain regions. These results demonstrate that prenatal morphine alters the content and turnover of NE in a sexually dimorphic manner in specific brain regions of male and female rats, suggesting alterations in the density of terminals and/or utilization of NE. These sexually dimorphic alterations in hypothalamic NE induced by prenatal morphine may be related to the changes observed in adult male and female sexual behavior in our previous work.