Amphetamine sensitization of hallucinatory-like behaviors is dependent on prefrontal cortex in nonhuman primates.

BACKGROUND

Repeated amphetamine (AMPH) exposure in nonhuman primates produces a chronic state of monoamine dysregulation and long-lasting changes in behaviors elicited by acute AMPH (including tracking, grasping "at thin air," manipulating nonapparent stimuli, and hypervigilance) in a manner that bears a marked resemblance to symptoms of both amphetamine psychosis and paranoid schizophrenia. These abnormal responses have historically been referred to as psychotomimetic or hallucinatory-like. In contrast to negative symptoms and cognitive deficits, the positive symptoms of schizophrenia including hallucinations have not traditionally been linked to prefrontal dysfunction.

METHODS

The dorsomedial (9/8B), dorsolateral (46/8A), and inferior (45/12) sectors of prefrontal cortex were lesioned, singly or in combination. Lesioned and nonlesioned control monkeys were sensitized over a 6-week period using an intermittent schedule of escalating low doses of AMPH. Behavioral responses to acute AMPH after chronic exposure were compared with preexposure responses.

RESULTS

Bilateral lesions of prefrontal cortex performed before subchronic AMPH suppressed the sensitization of hallucinatory-like behaviors but markedly enhanced locomotor sensitization compared with control animals.

CONCLUSION

These findings indicate that the primate prefrontal cortex may be a substrate for the development of the full complement of behaviors elicited by AMPH sensitization, including hallucinatory-like behaviors.