Continuous recording of locomotor activity in groups of rats: postweaning maturation.

A method was developed for continuous recording of locomotor activity in ten groups of rats housed in standard plastic cages under controlled lighting conditions. An inexpensive pressure transducer detected movements in the cage, and a light resistor monitored the lighting. The output voltages from the sensors were digitized, integrated for 5 s, and stored for off-line analysis. The data from separate cages were averaged for the detection of statistical differences between the experimental groups. The method was applied to study maturational changes after weaning. Wistar rats were recorded from 21 to 62 days of age under 12/12 h light/dark cycle. The cumulative activity distributions of the pups of 4 and 5 weeks of age differed significantly from those of 7-9 weeks, or older. Differences between the rats aged 8 or 9 weeks and the older adults were less consistent, but still detectable. The cumulative activity distributions of the males and females did not differ significantly from each other.