PREOPTIC AREA INFUSIONS OF MORPHINE DISRUPT - AND NALOXONE RESTORES -PARENTAL-LIKE BEHAVIOR IN JUVENILE RATS

As in the adult lactating female, opioids disrupt (and naloxone restor es), parental behavior in juvenile rats (similar to 25 days of age). B ecause the preoptic area regulates the display of parental behavior in lactating females, we examined its parental behavior role in the juve nile rat. At 21 days of age, juvenile rats were implanted with bilater al cannulae aimed at the preoptic area using a modified Kopf stereotax ic and extrapolating from a developing-rat brain atlas [58], and divid ed into two groups: initiation and maintenance. On day 25, the Initiat ion group received bilateral infusions of either morphine (0.50 mu g), saline (0.25 mu l), or morphine plus naloxone (0.25 mu g). Thirty min utes later, they were exposed to three 1-6-day-old pups; the maintenan ce group was exposed to pups until they displayed 2 consecutive days o f parental behavior, then infused. Morphine disrupted parental behavio r in both the Initiation and Maintenance groups, and naloxone restored the behavior to control/saline levels, Parental behavior in the juven ile animal of both sexes, therefore, is under opioid regulation that p arallels the adult female. (C) 1997 Elsevier Science Inc.