DAILY RHYTHMS OF HEART-RATE, TEMPERATURE AND LOCOMOTOR-ACTIVITY ARE MODIFIED BY ANESTHETICS IN RATS - A TELEMETRIC STUDY

The aim of this study was to evaluate the effect of anaesthesia (ether or ketamine) on daily rhythms of temperature (T), heart rate (H) and locomotor activity (A) in unrestrained rats by using implanted radio-t elemetry transmitters. T, H and A were measured every 10 min, in Wista r male rats, and analysed using Cosinor. The mean+/-SEM days needed, a fter surgical implantation, to detect a daily rhythm in H, T and A wer e also assessed. Six rats were anaesthetized for about 50 min either b y ketamine or ether in a 3 by 3 cross-over design. Mesors, amplitudes and acrophases of T, H and A were calculated three days before (D-3; D -2; D-1), the day of anaesthesia (D0) as well as the three following d ays (D1; D2; D3). ANOVA was performed in order to detect, firstly a po ssible effect due to the order of application of anaesthesia, secondly a significant difference between ether or ketamine-induced anaesthesi a and finally a modification of the mesors, amplitudes and acrophases of T, H and A, induced by each anaesthesia, for D0, D1, D2 and D3 when compared to D-1. Our results indicate: (1) Alterations of the acropha ses, mesors and amplitudes, except for the amplitude of A, of the dail y rhythms of T, H and A on D0 of ketamine anaesthesia while regarding ether anaesthesia only amplitude of T and H and acrophase of A were mo dified on D0. Some of these modifications were still observed on the d ays following anaesthesia. A significant difference between ether and ketamine-induced anaesthesia was also observed. (2) A non-detection of T, H and A daily rhythms after surgical implantation, which was not o bserved after injection of either ether or ketamine alone. Almost 10 d ays were needed to detect a significant daily rhythm for T, H and A. T he authors suggest that, the general anaesthetic agent was responsible for a perturbation of the mesors, amplitudes and acrophases of the da ily rhythms of H, T and A while the non-detection of these rhythms aft er implantation was more due to the surgical aggression.