Animal models for the study of the effect of prolonged stress on lactation in rats.

The suppressive effect of stress on lactation is well acknowledged. Animal models used to study this problem have used primarily acute stressors. As such, they are not adequate for the study of the effect of prolonged stress on lactation. This study aimed at developing a paradigm(s) in rats for the study of the effect on lactation of prolonged exposure to a stressful situation. Two models were examined. The first consisted of a separation paradigm whereby dams had 1, 2, 4, or 6 contacts per day with their pups, but only for a total of 4 h per day. The second model implicated the introduction of a male intruder into the home cage during the 12-h light period. Both protocols were implemented for four consecutive days beginning on Days 10/11 postpartum. Milk release was measured on Day 13/14 postpartum. For both models, milk release was significantly reduced following the preexposure period. During the assessment of milk release, maternal behavior of the experimental and control animals was similar at all times. It is advanced that these two rat models of stress are appropriate for the study of lactation following a prolonged exposure to stress.