Lack of M muscarinic receptors in the striatum, thalamus and intergeniculate leaflet alters the biological rhythm of locomotor activity in mice.

The deletion of M muscarinic receptors (MRs) changes biological rhythm parameters in females. Here, we searched for the mechanisms responsible for these changes. We performed biological rhythm analysis in two experiments: in experiment 1, the mice [C57Bl/6NTac (WT) and M MR -/- mice (KO)] were first exposed to a standard LD regime (12/12-h light/dark cycle) for 8 days and then subsequently exposed to constant darkness (for 24 h/day, DD regime) for another 16 days.

Acute restraint stress modifies the heart rate biorhythm in the poststress period.

We studied the changes in the heart and the activity biorhythms in mice exposed to acute (one 120-minute session) and repeated (7 two-hour sessions) restraint stress in 129J1/CF1 mice (WT) and in mice without M muscarinic receptors (MKO) during the prestress period, during stress (STR) and for five days after the last stress session (POST). There were changes in the mesor (a midline based on the distribution of values across the circadian cycles; decreased in MKO by 6% over all POST), day means (inactive period of diurnal rhythm in mice; higher in MKO and further increased on STR and on the second to the fifth POST) and night means (active period; lower by 13% in MKO and remained decreased in STR and in POST). The total area under the curve was decreased both in the WT and MKO on STR and in all POST.

Brain region-specific effects of immobilization stress on cholinesterases in mice.

Brain acetylcholinesterase (AChE) variant AChE expression increases with acute stress, and this persists for an extended period, although the timing, strain and laterality differences, have not been explored previously. Acute stress transiently increases acetylcholine release, which in turn may increase activity of cholinesterases. Also the AChE gene contains a glucocorticoid response element (GRE), and stress-inducible AChE transcription and activity changes are linked to increased glucocorticoid levels.