Dopaminergic neurons in the nigro-striatal and mesolimbic pathways: mediation of specific effects of D-amphetamine.

The administration of d-amphetamine (15 mg/kg, i.p.) to rats causes stereotypy, hypothermia among animals placed in a cold environment, and paradoxical behavioral thermoregulation (i.e., animals in a cold environment choose not to place themselves under the beam emitted by a heat lamp). These effects are blocked in animals lesioned unilaterally in the mesolimbic dopaminergic projections to the olfactory tubercule and nucleus accumbens. In contrast, a unilateral lesion destroying the nigro-striatal projections within the caudate nucleus blocks none of these responses, and actually potentiates the induction of stereotypy by d-amphetamine. Both lesions cause the animal to exhibit rotational behavior in response to the subsequent administration of d-amphetamine. These observations suggest that the mesolimbic dopaminergic projections mediate some of the behavioral and visceral effects of d-amphetamine.