Daily change in pineal N-acetyltransferase activity in a diurnal mammal, the ground squirrel

Pineal N-acetyltransferase (NAT) activity in the ground squirrel, a diurnal mammal, was found to have a daily fluctuation with peak activity during the dark time. This same daily change is found in nocturnal mammals and diurnal birds. NAT may play an important role in keeping track of light and dark cycles.