Seasonal variations in the circadian activity of AChE in the brain stem reticular formation of mice under normal and constant light regimens.

AChE activity in mouse brain stem reticular formation was studied at 4 hr intervals for 48 hr at 4 different times of the year under normal (LD 12/12) and constant light (LL) regimens. Under both illumination regimens, a significant ultradian rhythm of AChE activity was observed. In the investigated seasons of the year, changes in AChE behaviour were limited to mean activity of the enzyme (median) as well as to the amplitude and acrophase of the rhythm.