Prenatally undernourished rats show increased preference for wheel running v. lever pressing for food in a choice task

Maternal nutrition during pregnancy has a significant influence in establishing patterns of metabolism and postnatal behaviours in offspring, and therefore shapes their risk of developing disorders in later life. Although it is well established that a mismatch between food consumption and energy expenditure leads to obesity and metabolic dysregulation, little research has investigated the biological origin of such behaviour. We conducted the present experiments to investigate effects of early-life nutrition on preference between wheel running and lever pressing for food during adult life. To address this issue we employed a well-established experimental approach in the rat which has shown that offspring of mothers undernourished during pregnancy develop obesity and metabolic disorders when kept under standard laboratory conditions. Using this experimental approach, two studies were conducted where offspring of ad libitum-fed dams and dams undernourished throughout pregnancy were given the choice between wheel running and pressing a response lever for food. Across subsequent conditions, the rate at which the response lever provided food was varied from 0·22 to 6·0 (study 1) and 0·19 to 3·0 (study 2) pellets per min. Compared with the control group, offspring from dams undernourished during pregnancy showed a consistently greater preference for running over lever pressing for food throughout both experiments of the study. The results of the present study provide experimental evidence that a mother's nutrition during pregnancy can result in a long-term shift in her offspring's lifestyle choices that are relevant to obesity prevention. Such a shift, if endorsed, will have substantial and wide-ranging health consequences throughout the lifespan.

Self-Punishment for Responding by Monkeys during Extinction of Discriminated Avoidance: Effects of Previous Stimulus Change Reinforcement

Two groups of rhesus monkeys acquired a discriminated avoidance response (lever-pressing) under different training procedures. One group was trained using a conventional escape-avoidance procedure for 6 training sessions. The other group received one escape-avoidance session following 5 training sessions with stimulus-change reinforcement in which lever pressing momentarily terminated the light-tone combination later used as CS during avoidance training. Experience with stimulus change reinforcement facilitated acquisition of avoidance responding. Both groups showed self-punishment during extinction and did not differ significantly on this dimension.