CHANGES IN EXPERIMENTAL ANXIETY DURING PREGNANCY AND LACTATION

The animals' reactivity and the levels of experimental anxiety during pregnancy and lactation in female rats were studied using the burying behavior test. The three main parameters analyzed in this test were: t he cumulative burying behavior, the burying behavior latency, and the number of shocks necessary for displaying the behavior. The burying be havior was studied at the 7th, 14th, and 21st days of pregnancy and la ctation. An additional group tested 12 h after parturition was also in cluded. Simultaneously, in all animals, the ambulatory behavior was ev aluated. All results were compared with those obtained in a control gr oup of ovariectomized females. At the end of pregnancy a clear increas e in burying behavior latency accompanied by a decrease in cumulative burying behavior was observed. Similarly, a clear reduction in burying behavior immediately after parturition was found. The number of shock s necessary for displaying the burying behavior were not modified alon g pregnancy and lactation with the exception of a clear decrease for t he 7th lactation day. Changes in locomotor activity were observed at p regnancy, but not along lactation. These changes do not account for th e reduction in burying behavior observed at the 14th gestation day. Da ta related to the reduction in burying behavior observed during gestat ion are discussed on the possible participation of progestins, while t hose found during lactation are discussed on the bases of the variatio ns in serotonin and endorphins that normally occur during this period.