8-[3H]hydroxy-2-(di-n-propylamino) tetralin binding sites in goldfish retina.
The binding sites of 8-[3H]hydroxy-2-(di-n-propylamino)tetralin ([3H]DPAT) were characterized in the retina of goldfish in order to evaluate the selectivity of the ligand for serotonin1A (5HT1A) receptors. Specificity of the binding was performed in the presence of serotonergic and dopaminergic agonists and antagonists. Buspirone, spiroxatrine and 5-methoxy-N,N-dimethyltryptamine were potent inhibitors, followed by propranolol, citalopram, imipramine and desipramine. Serotonin was not a potent inhibitor, and its interaction with the binding sites of [3H]DPAT was complex. Nomifensine displayed an important inhibition, however, other dopamine uptake blockers, such as bupropion and GBR-12909, were less potent. Haloperidol was also a good inhibitor, but the D1 receptor agonist, SKF-38393, the D2 receptor antagonist, sulpiride, and dopamine did not inhibit the binding. GppNHp inhibited the binding in the micromolar range. The analysis of saturation experiments by isotopic dilution, using buspirone to determine nonspecific binding, revealed two sites. The number of binding sites defined by buspirone were higher than the ones defined by nomifensine. The specific binding, using buspirone for definition, was reduced by the intraocular injection of 6-hydroxydopamine. This investigation demonstrates that [3H]DPAT labels 5HT1A receptors in goldfish retina, but also interacts with a non-5HT receptor site. These receptors seem to be localized in dopaminergic neurons.
Lima
L
L
Laboratorio de Neuroquímica, Centro de Biofisica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, Caracas.
Schmeer
C
C
Urbina
M
M
D000818:Animals; D001665:Binding Sites; D002065:Buspirone / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D065127:Dopamine D2 Receptor Antagonists; D006054:Goldfish; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007700:Kinetics; D009627:Nomifensine / Q000494:pharmacology; D011869:Radioligand Assay; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000378:metabolism; D011985:Receptors, Serotonin / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D013764:Tetrahydronaphthalenes / Q000378:metabolism*; D014316:Tritium
D065127:Dopamine D2 Receptor Antagonists; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D014316:Tritium; D009627:Nomifensine; D006165:Guanylyl Imidodiphosphate; C031349:7-hydroxy-2-N,N-dipropylaminotetralin; D002065:Buspirone