A longitudinal study of the relationship between aging and the duration of hexobarbital hypnosis in male CFN rats.

The duration of hexobarbital hypnosis was determined for individual male CFN rats at three month intervals over their total adult lifespan. The mean duration of hexobarbital hypnosis for the cohort linearly with advancing age. However, the sleeptimes for individual rats fell into one of four categories (gradual increase, terminal step increase, no change, or not possible to assign) when assigned as a function of duration of response to the barbiturate over the lifespan of the animals. These results suggest that the generally well-accepted increase in duration of drug response in aging animals is neither a ubiquitous nor concomitant feature of aging. Furthermore, the varying results obtained for individual animals in this longitudinal study point out the possible error which may be attendant when utilizing pooled tissue extracts to examine hepatic monooxygenase activity in vitro in senescent rodents.