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.