CIRCADIAN PHASE-SHIFTING ASSOCIATED WITH ROUTINE CAGE MAINTENANCE - ARETROSPECTIVE ANALYSIS

Stimuli that evoke behavioral activation can phase-shift free-running circadian activity rhythms in Syrian hamsters. Activation-induced phas e shifting is characterized by a phase-response curve (PRC) that is di ssimilar to the PRC for photic phase shifting, and recent studies indi cate that complex interactions may occur between photic and non-photic phase shifting. Since animals in the laboratory may be exposed to bot h photic and behaviorally activating stimulation during routine cage m aintenance procedures, we performed a retrospective analysis of possib le phase shifts associated with cage cleaning in individually housed h amsters maintained in either constant darkness (DD) or dim red light ( RR) during the course of an ongoing study of drug-induced phase shifti ng. All cage cleanings were conducted under RR and were separated from drug treatments by at least one week. The results indicated that both photic and non-photic phase shifts could be induced by routine cage m aintenance procedures, depending on the circadian timing of the proced ure, on lighting conditions, and on the degree of evoked activity.