Aging alters amphetamine-induced stereotyped gnawing and neostriatal elimination of amphetamine in mice

Amphetamine-induced compulsive gnawing was assessed in C57BL/6J male mice (4, 10 and 29 months old). The 29-month old mice displayed a longer latency before initiation of the compulsive-gnawing response and a longer duration of compulsive-gnawing response than either younger age group. Following administration of 10 mg/kg of ³H-amphetamine sulfate neostriatal amphetamine levels were equivalent for the first hour for all age groups, but the oldest group of mice has a longer amphetamine elimination half-life from the striatum despite no change in the elimination of amphetamine from the plasma. These changes suggest that in old mice there is an altered time course of stereotyped gnawing response to amphetamine. Also, plasma amphetamine levels may be less reliable as a measure of brain amphetamine levels in old age.