[3H]TCP: a new tool with high affinity for the PCP receptor in rat brain.

PCP binding sites have previously been demonstrated in the central nervous system with [3H]PCP. We now describe the binding properties to rat brain membranes of [3H]TCP, a PCP derivative. It is very advantageous to use [3H]TCP instead of [3H]PCP for the 3 following reasons: (i) it has a better affinity (Kd = 7.4 nM) for PCP binding sites than PCP itself; (ii) it dissociates slowly from its binding sites (t 1/2 = 20 min); (iii) the non-specific binding component obtained with [3H]TCP is much lower than that found with [3H]PCP.