Start, stop, reduce, or maintain? How training and detraining during pregnancy shape maternal memory, behavior, and mother-pup interaction after maternal separation

Maternal separation (MS) leads to changes in maternal behavior. Maternal exercise could be a potent modifier of maternal behavior (MB). Regular physical exercise is widely recommended but is frequently modified during pregnancy, so we tested whether stopping, starting, reducing, or maintaining the running intensity during pregnancy can protect dams from MS-induced behavior and memory alterations, as well as influence mother-pup bonding. Female rats were divided into six groups: non-exercised mothers that were not submitted to MS (Control); non-exercised mothers submitted to MS (MS); mothers that ran (physical exercise) only before pregnancy and were submitted to MS (PRE+MS); mothers that started to run at the beginning of pregnancy submitted to MS (GEST+MS); mothers that ran before pregnancy and reduced the running intensity during pregnancy and were submitted to MS (RED+MS); and, mothers that ran at the same intensity before and during pregnancy and were submitted to MS (EQUAL+MS). We performed MS from PND 1 to 10, three hours per day. We assessed MB for 30 min after MS from PND 1 to 5. We assessed object recognition (OR) memory before and during pregnancy and after weaning. We assessed maternal preference (MP) one week after weaning. We measured hippocampal lipid peroxidation and catalase levels 24 h after the ending of all tests. PRE+MS leads to detraining and memory deficits at the end of pregnancy and after weaning. MS, PRE+MS, and RED+MS increased the time spent in the nest. GEST+MS mothers preferred contact with their male and female offspring after weaning. GEST+MS prevents OR deficit after weaning. PRE+MS showed increased lipid peroxidation after weaning. MS increased catalase levels; all exercised groups prevented this effect.