Thermotaxis in neonatal rat pups.

Deprived and nondeprived 3- and 6-day-old rat pups were tested on a thermal gradient for thermotaxis. Deprived 3-day olds demonstrated a marked thermotaxic responsiveness that was not observed in nondeprived 3-day olds or in deprived and nondeprived 6-day olds. Deprived 3-day olds did not show a strong thermal orientation immediately, but the distance moved by pups increased with repeated trials on the gradient. These findings demonstrate that neonatal rats are capable of thermotaxis, but that factors of age, deprivation and repeated handling determine pups' responsiveness to thermal gradients.