[3H](+)-7-OH-DPAT and [3H]pramipexole binding in the striatum and nucleus accumbens of Sprague-Dawley and Fischer-344 rats.
The binding of the D2-like agonists, (+)-7-hydroxy-N,N-di-n-[3H]propyl-2-aminotetralin (7-OH-DPAT) and [3H]pramipexole (2-amino-4,5,6-tetrahydro-6-propylaminobenzthiazole; MIRAPEX) were determined in membranes from adult male Sprague-Dawley and Fischer-344 rats. Saturation analysis, which optimized binding to D3 receptors, revealed 3-6 fold differences in Bmax values between the two radioligands with no change in affinity. [3H](+)7-OH-DPAT labeled 41.4+/-4.1 to 61.8+/-3.0 fmol/mg protein in nucleus accumbens and striatal homogenates, yet [3H]pramipexole labeled only 7.0+/-1.2 to 18.9+/-5.3 fmol/mg protein. Regional differences with both radioligands were observed in Fischer-344 rats; the striatum exhibited a 52%-69% greater density of sites in comparison to the nucleus accumbens. These data suggest that D3 receptor density can vary significantly between animal strains depending on the radioligand used, and [3H]pramipexole identifies a different ratio of sites in the striatum and nucleus accumbens compared to [3H](+)7-OH-DPAT.
Wallace
D R
DR
Department of Pharmacology and Physiology, Oklahoma State University College of Osteopathic Medicine, Tulsa 74107-1898, USA. walladr@okway.okstate.edu
Owens
J
J
Booze
R M
RM
D000818:Animals; D052160:Benzothiazoles; D018491:Dopamine Agonists / Q000493:pharmacokinetics*; D008024:Ligands; D008297:Male; D017072:Neostriatum / Q000378:metabolism*; D009714:Nucleus Accumbens / Q000378:metabolism*; D000077487:Pramipexole; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D013764:Tetrahydronaphthalenes / Q000493:pharmacokinetics*; D013844:Thiazoles / Q000493:pharmacokinetics*
D052160:Benzothiazoles; D018491:Dopamine Agonists; D008024:Ligands; D013764:Tetrahydronaphthalenes; D013844:Thiazoles; D000077487:Pramipexole; C031349:7-hydroxy-2-N,N-dipropylaminotetralin