Comparison of [3H]WIN 35,428 Binding, a Marker for Dopamine Transporter, in Embryonic Mesencephalic Neuronal Cultures with Striatal Membranes of Adult Rats

Abstract

Abstract: In contrast to striatal membranes of adult rats, where high‐ (KD1= 34 nM) and low‐ (KD2= 48,400 nM) affinity binding sites for [3H]WIN 35,428 are present, in primary cultures of ventral mesencephalon neurons (CVMNs) only low‐affinity binding sites were found (KD= 336,000 nM). The binding of [3H]WIN 35,428 in CVMNs prepared from rat embryos was reversible, saturable, and located in cytosol. Although dopamine (DA) uptake blockers inhibited [3H]DA uptake at nanomolar concentrations in CVMNs, the displacement of [3H]WIN 35,428 binding in CVMNs by DA uptake inhibitors required 100‐8,000 times higher concentrations than were needed to displace [3H]WIN 35,428 binding in striatal membranes. Piperazine derivatives, e.g., GBR‐12909, GBR‐12935, and rimcazole, inhibited [3H]WIN 35,428 binding in CVMNs more effectively than did cocaine, WIN 35,428, mazindol, nomifensine, or benztropin. A positive correlation (r= 0.779; p < 0.001) was found between drug affinities for the striatal membrane sites labeled by [3H]WIN 35,428 and their abilities to inhibit DA uptake in CVMNs, whereas no correlation existed between the IC50 values of drugs that inhibited [3H]WIN 35,428 binding and [3H]DA uptake in CVMNs. The cytosolic [3H]WIN 35,428 binding sites may be a piperazine acceptor and may not be involved in the regulation of the DA transporter. Copyright © 1993, Wiley Blackwell. All rights reserved