MATERNAL STATE AFFECTS INTESTINAL CHANGES OF RAT PUPS AT WEANING

Two treatments of hooded rat (Rattus norvegicus) mothers after the bir th of their pups affected the stage of development at which their pups started to take solid food and showed an increase in the expression o f sucrase, an enzyme needed for digesting solid food. The pups of moth ers that became pregnant in a post-partum oestrus showed the changes s ignificantly earlier than those in the control group (Fig. 1A, B). The pups of mothers that had been mildly food-restricted after birth show ed the changes significantly later than those in the control group. In brief, the pups of the pregnant mothers weaned first, the control pup s next and those of food-restricted mothers weaned last. Differences i n the timing of weaning between the three groups occurred in the absen ce of differences in pup body weight at the time of weaning. Within ea ch experimental group, on the day in which sucrase expression showed t he first detectable increase, sucrase activity was strongly predicted by the weight of the pups shortly after birth (Fig. 3). Pregnant mothe rs put on weight rapidly before implantation and their pups prepared f or early weaning even though they did not differ in body weight from c ontrol pups (Fig. 4A, B). Food-restricted mothers were significantly l ighter than control mothers and, with lighter pups before weaning star ted, settled for a longer period of suckling.