[3H]7-OH-DPAT labels both dopamine D3 receptors and sigma sites in the bovine caudate nucleus.

The binding of [3H]7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) to membranes of the bovine caudate nucleus was characterized and shown to be heterogenous. While [3H]7-OH-DPAT labels the dopamine D3 receptor in this tissue (Ki = 4.8 nM), as shown by its sensitivity to dopamine and (-)-quinpirole, it also binds with high affinity (Ki = 48 nM) to sigma recognition sites. The present results demonstrate that [3H]7-OH-DPAT is a useful radioligand to label native D3 receptors in the bovine caudate, although care must be taken to assure its selectivity.