Diurnal fluctuation in striatal choline acetyltransferase activity and strain difference in brain protein content of...

Choline acetyltransferase (CAT) activity was measured in two brain regions of rat at different times of the day. A diurnal fluctuation of the CAT activity was found in the striatum with a high activity during the light period and a low activity during the dark period. In the hippocampus + cortex the CAT activity remained constant. A marked difference in the brain protein content was found between two strains of Sprague-Dawley rats. This finding emphasizes the importance of expressing enzyme activity both per g tissue and g protein especially when comparing data between different research groups.