Comparison of the density and distribution of brain D-1 and D-2 dopamine receptors in Buffalo vs. Fischer 344 rats.

In vitro autoradiography was used to compare the D-1 and D-2 receptor densities in brains from Buffalo (BUFF) and Fischer 344 (F344) rats. The latter strain has been proposed as a model for human attention deficit disorder with hyperactivity (ADDH). The radioligands [3H]-SCH 23390 and [3H]-sulpiride were used to selectively identify dopamine D-1 and D-2 receptors, respectively. Certain forebrain structures from F344 rats have a higher density of D-2 receptors, but similar numbers of D-1 receptors compared to BUFF rats. Scatchard analysis of D-2 binding (in caudate-putamen) revealed a Bmax of 10.52 +/- 1.62 fmol/mg tissue and Kd of 12.72 +/- 0.93 nM in F344 rats and 3.00 +/- 0.57 and 3.87 +/- 0.58, respectively in BUFF rats (n = 3). These results support the hypothesis that high D-2 levels are correlated with certain behavioral traits, e.g., high levels of spontaneous activity. A similar increase in D-2 receptors may be responsible for some of the behavioral manifestations of ADDH in children.