PERINATAL EXPOSURE TO MORPHINE ALTERS THE DENSITY, BUT NOT THE SENSITIVITY, OF DOPAMINE-RECEPTORS IN THE 10-DAY-OLD RAT-BRAIN

On gestation day 7, osmotic pumps containing morphine base, 66.5 mg/ml , or 0.9% sodium chloride vehicle were implanted into anesthetized pre gnant female rats to determine the effects of chronic perinatal exposu re to morphine on the neurochemical and behavioral development of 10-d ay-old rat offspring. There was a significant decrease in the density of D1 receptors in the nucleus accumbens (NAc) of offspring exposed to morphine. In contrast, D2 receptor density was significantly increase d in the NAc at this age compared with controls. Perinatal exposure to morphine significantly decreased the density of D2 receptors in the s triatum, but had no significant effect on the K-d of D1 or D2 receptor s in this brain area. Exposure to morphine also had no significant eff ect on the locomotor response of 10-day-old offspring to SKF 38393 com pared with pair-fed controls, nor was there a significant difference i n the response of experimental offspring to quinpirole compared with c ontrols. The results indicate that chronic perinatal exposure to morph ine alters the density, but not the sensitivity, of DA receptors in th e 10-day-old rat brain.