Exposure to repeated, intermittent d-amphetamine induces sensitization of HPA axis to a subsequent stressor.

Previous studies have demonstrated that exposure to psychostimulant drugs can produce a lasting cross-sensitization to the behavioral effects of stress. The main purpose the present study was, therefore, to determine the effects of psychostimulant cross-sensitization on the stress-induced release of adrenocorticotropic hormone (ACTH) and corticosterone (CORT). Rats were given a series of injections of d-amphetamine or vehicle in a regimen that has been shown previously to induce cross-sensitization to a stressor. After two weeks, half the animals in the drug and vehicle-treated conditions were subjected to 30 min restraint stress; the remaining animals served as non-stressed controls. Animals were then sacrificed and trunk blood was assayed for CORT and ACTH. Prior d-amphetamine had no effect upon levels of CORT and ACTH in the non-stressed animals. Following 30 min restraint stress, however, levels of both hormones were significantly higher in drug-treated animals compared to controls. A second experiment confirmed behavioral sensitization to the current schedule of d-amphetamine injections, and demonstrated neuroendocrine sensitization of ACTH and CORT to a subsequent drug challenge. The augmented release of CORT and ACTH observed in d-amphetamine-treated rats might have important implications for human disorders in which processes resembling neurochemical sensitization have been hypothesized to play an etiological role.