INVESTIGATION INTO THE ROLE OF CHOLECYSTOKININ (CCK) IN THE INDUCTIONAND MAINTENANCE OF MATERNAL-BEHAVIOR IN RATS

The biochemical regulation of maternal behavior has been extensively s tudied. Cholecystokinin (CCK), a gut peptide that is also present in t he brain, recently has been implicated in the onset of maternal behavi or in estrogen-primed virgin rats. The objective of the present set of studies was to delineate the role of CCK in the onset (Experiments 1- 3) and maintenance (Experiments 4 and 5) of maternal behavior in rats. In the first study intracerebroventricular (i.c.v.) administration of CCK was unable to stimulate the onset of maternal behavior in estroge n-primed virgin rats. Similarly, i.c.v. infusions of CCK into pregnant rats, starting on Day 17 of gestation (Experiment 2), did not advance the onset of maternal behavior. Moreover, when CCK-filled minipumps w ere implanted intraperitoneally in estrogen-primed virgin rats, the ra te of onset of maternal behavior was unaffected (Experiment 3). In con trast, direct infusions of CCK into the MPOA blocked the disruptive ef fects of P-endorphin on the maintenance of maternal behavior in postpa rtum lactating rats (Experiment 4). In addition, proglumide, a CCK rec eptor antagonist, disrupted maternal behavior in postpartum lactating rats by increasing latencies to retrieve and crouch over the young (Ex periment 5). These results support an involvement of CCK in the mainte nance, but not the onset, of maternal behavior in rats. (C) 1995 Acade mic Press, Inc.