Dopamine Receptor Inactivation in the Caudateputamen and Nucleus Accumbens Differentially Affects the Locomotor Activity of Young Rats

Event Center A & B

Microinjecting the alkylating agent EEDQ into the caudate-putamen (CPu) of adult rats both inactivates DA receptors and blocks DA mediated behaviors. In contrast, DA receptor inactivation in the CPu of preweanling rats causes a paradoxical increase in DA agonist-induced locomotor activity. We have hypothesized that the heightened behavioral responsiveness exhibited by EEDQ-treated preweanling rats is due to elevated levels of high affinity D2 receptors. In other words, an EEDQ-induced increase in the percentage of D2(High) receptors is proposed to more than compensate for the overall loss of DA receptors, thus resulting in enhanced behavioral responsiveness when challenged with a DA agonist drug (cocaine or NPA). The purpose of the present study was threefold: (1) to replicate the finding that EEDQ potentiates the behavioral effects of NPA when microinjected into the CPu; (2) to determine whether administering EEDQ into the nucleus accumbens (NAcc) also potentiates the effects of NPA; and (3) to examine whether the ability to potentiate or attenuate DA agonist-induced locomotion is influenced by the amount of striatal and accumbal tissue affected by EEDQ.