[H-3](-7-OH-DPAT AND [H-3]PRAMIPEXOLE BINDING IN THE STRATUM AND NUCLEUS-ACCUMBENS OF SPRAGUE-DAWLEY AND FISCHER-344 RATS())

The binding of the D2-like agonists, (+)-7-hydroxy-N,N-di-n-[H-3]propy l-2-aminotetralin (7-OH-DPAT) and [H-3]pramipexole amino-4,5,6-tetrahy dro-6-propylamino-benzthiazole; MIRAPEX(R)) were determined in membran es from adult male Sprague-Dawley and Fischer-344 rats. Saturation ana lysis, which optimized binding to D3 receptors, revealed 3-6 fold diff erences in Bmax values between the two radioligands with no change in affinity. [H-3](+)7-OH-DPAT labeled 41.4+/-4.1 to 61.8+/-3.0 fmol/mg p rotein in nucleus accumbens and striatal homogenates, yet [3H]pramipex ole labeled only 7.0+/-1.2 to 18.9+/-5.3 fmol/mg protein. Regional dif ferences with both radioligands were observed in Fischer-344 rats; the striatum exhibited a 52%-69% greater density of sites in comparison t o the nucleus accumbens. These data suggest that D3 receptor density c an vary significantly between animal strains depending on the radiolig and used, and [H-3]pramipexole identifies a different ratio of sites i n the striatum and nucleus accumbens compared to [H-3](+)7-OH-DPAT. (C ) 1998 Elsevier Science Inc.