Characterization of [3H]nisoxetine binding in rat vas deferens membranes: modulation by sigma and PCP ligands.
Sigma (sigma) and phencyclidine (PCP) receptor ligands, apart from their main effects on sigma receptors and NMDA receptor-mediated neurotransmission, have been found to interact with catecholamine systems in several central and peripheral tissues. In the present study the binding profile of [3H]nisoxetine ([3H]NIS), a selective marker of the noradrenaline transporter, has been characterized in rat vas deferens membranes to further study its modulation by a number of characteristic sigma and PCP ligands. The binding of [3H]NIS was found to be of high affinity (Kd = 1.63 +/- 0.36 nM), saturable, sodium-dependent and to a single population of binding sites (nH = 1.003 +/- 0.017). The maximal binding capacity was 1,625 +/- 500 fmol/mg of protein. Kinetic experiments gave a k(+1) of 3.9 x 10(7) min(-1)M(-1) and a k(-1) of 0.005 min(-1). The [3H]NIS binding was totally inhibited, with IC50 values in the micromolar range, by all the sigma and PCP ligands tested, with the following order of potency: haloperidol > dextromethorphan > dizocilpine > dextrorphan > (+)-3-PPP > PCP > tenocyclidine. This order correlates well with that described in other tissues using [3H]desmethylimipramine. The inhibition by all these compounds, except that of (+)-3-PPP, was competitive. These results suggest that sigma and PCP ligands bind, at low micromolar concentrations, to a site in the noradrenaline transporter that is labelled by [3H]NIS.
Pubill
D
D
Unitat de Farmacologia i Farmacognòsia, Facultat de Farmàcia, Universitat de Barcelona, Spain. pubill@farmacia.far.ub.es
Gasulla
D
D
Sureda
F X
FX
Camins
A
A
Pallàs
M
M
Escubedo
E
E
Camarasa
J
J
D000818:Animals; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D005473:Fluoxetine / Q000031:analogs & derivatives* / Q000378:metabolism; D008297:Male; D050484:Norepinephrine Plasma Membrane Transport Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D017478:Receptors, Phencyclidine / Q000378:metabolism*; D017480:Receptors, sigma / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D027981:Symporters; D014649:Vas Deferens / Q000378:metabolism*
D002352:Carrier Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D017478:Receptors, Phencyclidine; D017480:Receptors, sigma; C493226:Slc6a2 protein, rat; D027981:Symporters; D005473:Fluoxetine; C011386:nisoxetine; D012964:Sodium