Microinjections of dopamine agonists and cocaine elevate plasma corticosterone: dissociation effects among the ventral and dorsal striatum and medial prefrontal cortex

There is evidence suggesting the involvement of central dopamine (DA) systems in the regulation of plasma corticosterone (CORT). We examined whether or not microinjections of DA agonists and cocaine into three DA-rich terminal regions, the medial prefrontal cortex (MPC), ventral striatum (VStr) and dorsal striatum (DStr), would increase plasma CORT in Sprague–Dawley rats. The highest dose tested (18 nmol) of a mixture of the dopamine D 1 receptor agonist SKF 38393 and the D 2 agonist quinpirole (SKF/Quin) increased plasma CORT when injected into each of the three brain regions. Microinjections of the medium dose (i.e., 3 nmol) of SKF/Quin into the VStr also increased plasma CORT, while the injections into the MPC and DStr did not. Systemic pretreatment with haloperidol attenuated the elevated CORT induced by intra-VStr injections of SKF/Quin. Cocaine (25, 50, and 100 μg) also increased CORT when injected into the VStr, but not into the MPC or DStr. Microinjections of local anesthetics, lidocaine (100 μg) and procaine (100 μg), which have similar chemical structures to cocaine, into the VStr did not increase CORT. These results suggest that the VStr plays an important role in mediating the elevated plasma CORT induced by DA agonists and cocaine administration.