[H-3] GBR-12935 LABELS MAINLY THE PIPERAZINE ACCEPTOR SITE IN THE RATPREFRONTAL CORTEX

The binding characteristics of [H-3]GBR 12935, a ligand for the dopami ne (DA) transporter, have been extensively investigated in the striatu m. The present study was designed to characterize [H-3]GBR 12935-bindi ng to prefrontal cortex (PFC) in rats. This region receives a dense DA input from the ventral tegmental area and is suspected to play a majo r role in higher associative functions. We demonstrated high-affinity, saturable, mazindol-sensitive [H-3]GBR 12935-binding in the rat PFC; however, in contrast to the striatum, such binding was inhibited by in creasing concentrations of Na+. This fact, together with the irregular pattern of the association kinetics and the marked sensitivity of [H- 3]GBR 12935-binding to piperazine derivatives, indicates the possible presence of more than one [H-3]GBR 12935-binding site in the PFC. Furt hermore, it appears that [3H]GBR 12935 in the rat PFC labels mainly 't he piperazine acceptor site' and not the DA transporter.