Temperature reduction in neonatal mice: Effects on later behavior

The effects of body temperature reduction in neonatal C57BL/6J mice were studied in 2 experiments. Experiment I investigated the development of the thermoregulatory response of mice from 1 to 15 days of age in their nest and in an ambient environment of 22°C. The experimental conditions could then be specified to produce body temperature reduction of either 5 or 10°C for 10 min from day 1 through 15. In Experiment 2, effects of these body temperature reductions at day 1 to 5, 6 to 10, or 11 to 15 on subsequent behavior at 30 and 70 days of age were studied. Three control groups (handled, non‐temperature maintained; handled, temperature maintained; and nonhandled) were treated at the same age periods. Behavioral tests were open field, water runway, water maze (preference) and single‐alternation problem, and water submersion. No consistent behavioral effects could be attributed to body temperature reduction or to age at treatment in infancy. Mice receiving body temperature reduction of 5 and 10°C, or handling (with or without body temperature reduction) behaved differently from nontreated subjects on latency and activity measures in an open field; on the latency measure in the water maze (preference) test; on the errors and days to criterion measures in the single‐alternation water maze; and in time‐to‐submersion in water. The behavioral alterations of the treated groups could be interpreted to represent reduced emotionality, and improved performance and learning ability resulting from the neonatal experiences.