Circadian behavioural resetting to NMDA in aged mice. Central injections of NMDA reset behavioural circadian rhythms in young animals (A, B, p<0.01, n= 9), however had very little impact in older mice (A, B, n= 11). NMDA microinjections, in vivo, result in behavioural clock resetting in a similar manner to light. This response was significantly reduced in older animals (p<0.01, A). Representative actograms for a young (B) and aged (C) mouse undergoing either NMDA or saline treatments; day and time of injections is indicated by ✶.