A mobilizable pool of d-amphetamine in adipose after daily administration to rats

Six daily injections (subacute) of 2.5 mg d-amphetamine/kg resulted in a 60% higher concentration of unchanged drug in adipose compared with adipose from rats injected once. Subacute treatment also resulted in 30% less amphetamine in brain one hour after injection, when the animals were killed for tissue analysis. Moderate stress, in the form of foot shock for fifteen minutes, terminating fifteen minutes prior to sacrifice, mobilized the drug from adipose and doubled brain levels of amphetamine in the subacute group. Brain levels in the group given a single dose of drug were unaltered by shock, but heart content of amphetamine was increased 30% as a result of shock. It is concluded that enhanced reactivity to some of the behavioral effects of amphetamine, upon repeated administration, may be due to cumulation of the drug in mobilizable pools.