Mesolimbic and Nigrostriatal Dopaminergic Systems: Behavioral Neuropharmacology.

This dissertation has examined drug-induced behaviors associated with the nucleus acumbens and striatum. The use of 6-Hydroxydopamine to anatomically enhance a behavior emanating from one of the above structures by allowing doses of drugs low enough to prevent major behavioral competition from the other was only partially successful. Thus, locomotor hyperactivity and circling were enhanced by 6-OHDA-induced lesions of the nucleus accumbens and the medial forebrain bundle, respectively. Bilateral lesions of the striatum did not result in simple enhancement of stereotypic behavior, but instead caused an unique, self-directed behavior termed stereotypic grooming. Competition between the nucleus accumbens and the striatum for behavioral expression was evident in most of these studies. For example, in control animals stereotypic behavior masked locomotor activity except for a very narrow dose range of apomorphine. Likewise, circling behavior in the output model was reduced at the higher doses of apomorphine by stereotypic grooming. Stereotypic grooming itself in animals with bilateral striatal lesions was not affected by accumbens lesions. Circling behavior in the last section emphasized the importance of the nucleus accumbens in both the nigrostriatal and striatonigral models.