[3H]-YM-09151-2 binding sites in human brain postmortem

The controversial and limited data on the distribution of dopamine (DA) receptors of type 4 (D4) in the human brain prompted us to explore their density and pharmacological characteristics in the prefrontal cortex, striatum and hippocampus, through a series of binding assays. Brain samples were taken during autopsy from seven subjects. Tissue homogenates were incubated with increasing concentration of [3H]-YM-09151-2, a D2-like receptor antagonist, and L-745,870 and/or sulpiride to define the non-specific binding, while PPAP was used to block sigma receptors. The results showed a low density of D4 receptors in the hippocampus only, with a preponderance of D2/D3 and sigma receptors in the prefrontal cortex and striatum. In conclusion, these findings underline that it is possible to label D4 receptors by means of [3H]-YM-09151-2, provided that D2, D3 and sigma receptors are blocked.