The influence of illumination upon general activity in normal, blinded, and castrated male white rats.

Abstract

The activity of [male] rats was measured in an especially designed bird cage type of recording apparatus and the effects on activity of various factors were measured. The following conclusions seem well supported by the evidence: A daily activity cycle exists; 3- of the activity occurring in the light and f in the dark. Changing the light-dark cycle during the 24 hrs. of a day results in the rats changing the hourly activities to correspond so that after a wk. or two the same light-dark cycle is shown. The daily cycle is observable in blind rats but is less pronounced than in the normal. The cycle in blind rats is not affected by light shifts showing the presence of an internal factor controlling the cycle. Castrated animals, although less active than normals, show the same variations as do the normals, indicating that the gonada probably are not an important internal regulator of the c.ycle. The activity cycle of c? rats is complexly detd.; both external and internal factors being important determiners.