Investigation into the Role of Cholecystokinin (CCK) in the Induction and Maintenance of Maternal Behavior in Rats

Abstract

The biochemical regulation of maternal behavior has been extensively studied. Cholecystokinin (CCK), a gut peptide that is also present in the brain, recently has been implicated in the onset of maternal behavior 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 estrogen-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 were implanted intraperitoneally in estrogen-primed virgin rats, the rate of onset of maternal behavior was unaffected (Experiment 3). In contrast, direct infusions of CCK into the MPOA blocked the disruptive effects of β-endorphin on the maintenance of maternal behavior in postpartum lactating rats (Experiment 4). In addition, proglumide, a CCK receptor antagonist, disrupted maternal behavior in postpartum lactating rats by increasing latencies to retrieve and crouch over the young (Experiment 5). These results support an involvement of CCK in the maintenance, but not the onset, of maternal behavior in rats.