DAILY VARIATION IN ACTIVE GLYCOGEN-PHOSPHORYLASE PATCHES IN THE MOLECULAR LAYER OF RAT DENTATE GYRUS

A larger number of discrete patches of active glycogen phosphorylase ( alphaGP) were found in the molecular layer of the hippocampal dentate gyrus in rats sacrificed during the daily dark phase (xBAR = 28.7/sect ion) than during the light phase (xBAR = 7.8/section). Light-dark diff erences in the patterns of alphaGP may reflect circadian differences i n metabolic demand in the hippocampus. Patch sizes were consistent wit h increased activation of single astrocytes or perisynaptic astrocyte clusters by focal input at night.