Intrastriatal injection of D-1 or D-2 dopamine agonists affects glucose utilization in both the direct and indirect pathways of the rat basal ganglia

Two distinct pathways are thought to connect the striatum to the basal gang lia output nuclei: a direct pathway, originating from neurons bearing dopam ine, D-1 receptors and an indirect pathway, originating from neurons expres sing D-2 receptors. It has been recently suggested, however, that dopamine receptor sub-types may co-localize and co-operate in the striatum. We sough t to verify the functional segregation of the two pathways by measuring cer ebral glucose utilization following intrastriatal injection of selective D- 1 (SKF 38393), D-2 (quinpirole), or non-selective indirect (amphetamine) an d direct (apomorphine) dopamine agonists, in freely-moving rats. All drugs- regardless of receptor selectivity - reduced glucose utilization in nuclei of both the direct and indirect pathways, thus lending further support to t he existence of a functional co-operation of striatal D-1 and D-2 receptors . (C) 2001 Published by Elsevier Science Ireland Ltd.