Identification of a subregion within rat neostriatum for the dopaminergic modulation of lateral hypothalamic self-stimulation.

Experiments were conducted to test the hypothesis that the involvement of neostriatal dopaminergic transmission in lateral hypothalamic self-stimulation might be specific to a striatal subregion. Crystalline application of dopamine or D-amphetamine increased self-stimulation rate only when made to ventral anterior striatum (VAS); more dorsal or posterior applications were ineffective. A comparison of dose-response functions for dopamine using solution injections in VAS and posterior striatum (PS) confirmed that only VAS was responsive. Injections or applications of 6-hydroxydopamine suppressed responding only when made into VAS. Haloperidol injections decreased responding only for VAS and not PS injection sites. Applications or injections of scopolamine often increased responding when made into VAS, but this effect was unreliable. Applications or injections of scopolamine to more posterior sites consistently suppressed responding. It was concluded that dopaminergic transmission in VAS, alone among the striatal sites tested, is facilitatory on hypothalamic self-stimulation. The effects of drug applications to nucleus accumbens were generally similar to VAS, and it was suggested that these areas may be functionally similar. An examination of the known afferents to VAS indicated that this area of neostriatum, like n. accumbens, may be influenced by activity in limbic structures. This anatomy may help provide an understanding of how neostriatum, traditionally considered to have a motor function, might be involved in central reward processes.