Evaluations of ventral pallidal dopamine receptor activation in behaving rats

Recent evidence justifies the inclusion of the ventral pallidum/substantia innominata (VP) into the category of dopaminoceptive brain regions. Since the VP is known to mediate both cognitive and motoric processes, the present study employed intracerebral microinjections of dopamine directly into the VP of rats to determine if the catecholamine influences these processes. Dopamine concentrations of up to 10 micrograms were ineffectual in altering performance parameters in a working memory task. However, concentrations as low as 0.01 micrograms increased locomotion in an open field. The magnitude of this response was related to the dopamine dose injected and the effect was attenuated by systemic pretreatment with the dopaminergic antagonist, flupentixol. These studies suggest that dopamine neurotransmission at the level of the VP may be important in the locomotor functions attributed to ascending dopamine systems.