‘Emotionality’ and adrenal cortical function: Effects of strain, tests, and the 24-hour corticosterone rhythm

Abstract

Summary Open-field testing of rats and mice did not yield significant behaviour-steroid correlations in experiment 1. In experiment 2 albino and hooded rats maintained under a 12 hr light-dark regimen were observed in a reaction-to-handling situation and an open-field at the peaks and troughs in the previously determined 24 hr rhythm in adrenal cortical activity. Strain differences were observed in the reaction-to-handling test and to a lesser extent in the open-field, and were independent of the time of testing. Hooded animals had heavier adrenal glands than albinos, but neither adrenal weight nor plasma and adrenal corticosterone values were related to emotionality. The plasma corticosterone response to behavioural testing varied as a function of the test and the time at which it occurred.