Immobilization-induced changes in the response of striatal neurons to dexamphetamine

Bipolar multiple unit recording electrodes were implanted in the striata of male Long-Evans rats 5-7 days prior to experimentation. In subsequent experiments, striatal neuronal activity in response to dexamphetamine (1.0 or 2.5 mg/kg i.p.) was recorded in either freely moving or immobilized, artificially-respired rats. Whereas dexamphetamine produced only excitation of striatal neurons in freely moving animals, a multiplicity of responses, ranging from excitation to inhibition, and including biphasic as well as no change responses were observed in immobilized animals. It is concluded that the absence of dexamphetamine-induced behavior in immobilized animals modifies the striatal neuronal response to dexamphetamine, possibly through alteration of the activity of excitatory striatal afferents.