The Effect of General Anaesthesia on Circadian Rhythms in Behaviour and Clock Gene Expression of Drosophila melanogaster

Abstract

General anaesthesia (GA) is implicated as a cause of postoperative sleep disruption and fatigue with part of the disturbance being attributed to a shift of the circadian clock. In this study, Drosophila melanogaster was used as a model to determine how Isoflurane affects the circadian clock at the behavioural and molecular levels. We measured the response of the clock at both of these levels caused by different durations and different concentrations of Isoflurane at circadian time 4 (CT4). Once characterized, we held the duration and concentration constants (at 2% in air for 6 h) and calculated the phase responses over the entire circadian cycle in both activity and period expression. Phase advances in behaviour were observed during the subjective day, whereas phase delays were associated with subjective night time GA interventions. The corresponding pattern of gene expression preceded the behavioural pattern by approximately four hours. We discuss the implications of this effect for clinical and research practice.

Keywords: Drosophila; circadian clock; general anaesthesia; locomotor activity; period gene expression; phase response curve.

Figure 1

(A) The effect of anaesthetic duration on phase (2% Isoflurane treatment centred at circadian time 4 (CT4)). (B) The effect of anaesthetic concentration (6 h anaesthesia centred at CT4). Data shown as mean with SEM error bars. Asterisks denote significant difference from the control (Students t-test, * p < 0.002) shown uncorrected for multiple comparisons. See also Table S1.

Figure 2

Behavioural phase response curve (PRC) for anaesthesia (6 h of 2% Isoflurane, centred around the respective CT) administered over the circadian cycle in wild-type D. melanogaster. Solid circles indicate the mean phase shift to GA, and open circles indicate the associated control. Error bars indicate standard error of the mean. Significant differences compared to the CT4 bin calculated by general linear model (GLM) analysis indicated by asterisks, ** p < 0.01, *** p < 0.001. See also Table S5 and Figure S1.

Figure 3

Phase response curve of per expression to anaesthesia (6 h of 2% Isoflurane) administered over the circadian cycle in 8.0-luc transgenic D. melanogaster. Solid circles indicate the mean phase shift to GA, and open circles indicate the associated control. Error bars indicate standard error of the mean. Significant differences compared to the CT4 bin calculated by GLM analysis indicated by asterisks, * p < 0.05, *** p < 0.001. See also Table S6 and Figure S2.