ENDOGENOUS CHOLECYSTOKININ REDUCES VOCALIZATION IN ISOLATED 10-DAY-OLD RATS

Devazepide, the cholecystokinin (CCK) A receptor blocker, markedly and specifically affected the behavior of 10-day-old rats isolated from t heir mother and siblings. Whereas intraoral infusions of milk or fat, which cause CCK release, calmed infants, that is, reduced levels of ul trasonic vocalization, devazepide fully blocked this reduction. Devaze pide did not affect calming caused by sucrose infusions, which do not release CCK. Moreover, devazepide did not reduce the elevated pain lim en caused by milk or fat infusions. These data parallel earlier findin gs obtained with administration of exogenous CCK and implicate endogen ous CCK in the maintenance of infant steady state and calm. The possib ility that CCK contributes to the normal development of mother-infant affectional systems is discussed.