Behavioral and cardiac responses to a sudden change in environmental stimuli: effect of forced shift in food intake.
In order to test the possibility of a change in stress susceptibility induced by a forced change in activity rhythm, during control weeks food availability was restricted to the dark period only (fa-D) and to the light period only during the test week (fa-L). Stress susceptibility was measured on the basis of the decrease in heart rate (bradycardia) and an increase in freezing behavior in response to a sudden reduction in background noise. A significant increase in bradycardia both in magnitude and duration was observed during fa-L conditions as compared to the control fa-D condition. Also the duration of freezing behavior was increased during the fa-L condition. These results support the hypothesis that forced changes in circadian activities affect stress susceptibility. The significance of this finding for the incidence of stress pathologies is discussed.
Department of Animal Physiology, University of Groningen, Haren, The Netherlands.
J M
JM
Steenbergen
J M
JM
Koolhaas
J H
JH
Strubbe
B
B
Bohus
D000204:Activity Cycles; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D002940:Circadian Rhythm; D004562:Electrocardiography; D005247:Feeding Behavior; D006339:Heart Rate; D008297:Male; D009622:Noise; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000503:physiopathology*