Circadian Variations of Neurotransmitter Binding in Three Age Groups of Rats

Publisher Website
Google Scholar
Abstract
Binding in 14 ligand membrane receptor pairs and choline acetyltransferase activity were studied at 4 h intervals during a 24 h cycle (12:12 light:dary). Cortex, hippocampus, cerebellum, striatum and brainstem were prepared from 3, 12 and 24 mo. old male rats. Cholinergic, .alpha.- and .beta.-adrenergic, dopaminergic, serotonergic, gabaergic and opiate binding were determined. In the aged animals, the times of the binding maxima are no longer locked to the same time of the light:dark cycle, and the cycle phases themselves are shifted in comparison to those of the young and adult group. Cycle amplitudes were smallest in the 12 mo. old rats, increasing significantly in the 24 mo. group. The age changes in the overall (24 h) means fall into 4 different patterns, none of which shows a linear age-related decrease. This points out the great importance of including an adult group (12 mo.) in all aging studies on small mammals.