General Anaesthesia Shifts the Murine Circadian Clock in a Time-Dependant Fashion

Abstract

Following general anaesthesia (GA), patients frequently experience sleep disruption and fatigue, which has been hypothesized to result at least in part by GA affecting the circadian clock. Here, we provide the first comprehensive time-dependent analysis of the effects of the commonly administered inhalational anaesthetic, isoflurane, on the murine circadian clock, by analysing its effects on (a) behavioural locomotor rhythms and (b) PER2::LUC expression in the suprachiasmatic nuclei (SCN) of the mouse brain. Behavioural phase shifts elicited by exposure of mice (n = 80) to six hours of GA (2% isoflurane) were determined by recording wheel-running rhythms in constant conditions (DD). Phase shifts in PER2::LUC expression were determined by recording bioluminescence in organotypic SCN slices (n = 38) prior to and following GA exposure (2% isoflurane). Full phase response curves for the effects of GA on behaviour and PER2::LUC rhythms were constructed, which show that the effects of GA are highly time-dependent. Shifts in SCN PER2 expression were much larger than those of behaviour (c. 0.7 h behaviour vs. 7.5 h PER2::LUC). We discuss the implications of this work for understanding how GA affects the clock, and how it may inform the development of chronotherapeutic strategies to reduce GA-induced phase-shifting in patients.

The Effects of General Anaesthesia and Light on Behavioural Rhythms and GABAA Receptor Subunit Expression in the Mouse SCN

“…The GA-induced shifts shown here (and those in our previous paper [ 9 ]) may be mediated, at least in part, through the activation of different GABA A R subunits or configurations within the SCN. Our demonstration here that three different GABA A R subunits are expressed in the mouse SCN and show strong temporal changes over the course of the day, highlights the complex and dynamic role GABA is likely to play in the central clock.…”

“…If the mammalian circadian system was shown to respond in a similar manner to GA and light as honey bees, our previous demonstration in bees that the phase shifting effects of isoflurane can be ameliorated by the concurrent administration of light [ 7 ] would provide, at least theoretically, a means to reduce GA-induced phase shifting in mammals. Initial data on the effects of GA on mice in free-running conditions (DD) indicated that, unlike bees, the times of GA-induced phase shifts were not in antiphase to those of light, but occurred at similar circadian times (both GA and light causing delays between CT7 and CT18) [ 9 , 10 ]. The phase response curve presented here for the combined effects of isoflurane (2% for 4 h) and light on behavioural rhythms in mice further these findings.…”

“…GA-induced behavioural phase shifts not only persist in the presence of a light pulse, the magnitude of these shifts are similar to those induced following isoflurane administration under free-running conditions. If anything, shifts are moderately larger in magnitude than those observed in DD, with a maximum phase delay of −1.05 h (compared to −0.77 h in DD) [ 9 ]. The GA + Light PRC appears to sit in-between the PRCs for light alone and GA alone.…”

“…We have shown that GA can phase shift behavioural rhythms of honeybees ( Apis mellifera ) and Drosophila melanogaster in a time-dependent manner [ 6 , 8 ], and that these behavioural shifts are underpinned by changes in the expression of core clock genes. Most recently, we have demonstrated that the inhalational agent isoflurane causes robust and reproducible shifts in behaviour and PERIOD2 (PER2) expression in mice, with maximal shifts occurring between CT6 and CT16 [ 9 ].…”

“…Whether this occurs in mammals remains to be understood. There is, however, a fundamental difference in the timing of GA-induced phase shifts and their relationship to light-induced phase shifts in mammals, as the circadian times at which phase advances and delays occur with GA and light are not in antiphase (as they are in bees) with both GA and light causing delays between CT6 and CT18 in mice [ 9 , 10 ].…”