Comparison of [ 3H] Phencyclidine ([ 3H] PCP) and [ 3H] N- [1 - (2-thienyl) cyclohexyl] Piperidine ([ 3H] TCP) binding properties to rat and human brain membranes.

Abstract

The investigation of [ 3H] PCP and [ 3H] TCP binding properties to rat cerebrum and cerebellum resulted in the demonstration of multiple binding sites for the two drugs. In the two tissue preparations PCP had a lower affinity than TCP. In membranes from the cerebrum an equal number of high affinity binding sites were present for [ 3H] PCP and [ 3H] TCP. However, low affinity binding sites were two times more numerous for [ 3H] PCP than for [ 3H] TCP. In the cerebellum, the number of high and low affinity sites labeled by the two radioligands was identical, but the number of high affinity sites was about 7 fold lower than in the cerebrum. Taken together these results may indicate that in the cerebrum [ 3H] PCP labels other sites than NMDA/PCP receptor(s), maybe sigma receptors and/or the dopamine uptake complex. In human cerebral cortex samples [ 3H] TCP also bound to two different sites. The number of high and low affinity sites were 12 and 3 times, respectively, less abundant than in the rat cerebrum. Low affinity sites were of higher affinity (5 times) than corresponding sites in the rat brain. In the human cerebellum [ 3H] TCP binding parameters were identical to those measured in the same region in the rat.