Effect of putative melatonin receptor antagonists on melatonin-induced pigment aggregation in isolated Xenopus laevis melanophores.
The ability of putative melatonin receptor antagonists to antagonise melatonin-induced aggregation of pigment granules in cultured neural crest Xenopus laevis melanophores was examined. Neither ML 23 (N-(2,4-dinitrophenyl)-5-methoxytryptamine) nor 6-methoxy-2-benzoxazolinone showed agonist or antagonist activity. N-Acetyltryptamine and N-butanoyltryptamine were partial agonists; both compounds aggregated pigment granules in some cells, but also reversed melatonin-induced pigment agreggation in a fraction of the cells tested. In contrast, 2-benzyl N-acetyltryptamine (luzindole) did not show agonist activity (upto 10 microM) but did reverse the aggregating action of melatonin at 1 and 10 microM. Pretreatment of melanophores with luzindole shifted the melatonin concentration-response curve to the right.
Sugden
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Biomedical Sciences Division, King's College London, U.K.
D000818:Animals; D002449:Cell Aggregation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D008547:Melanophores / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008550:Melatonin / Q000494:pharmacology*; D010858:Pigmentation / Q000187:drug effects* / Q000502:physiology; D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter / Q000037:antagonists & inhibitors*; D014363:Tryptamines / Q000494:pharmacology; D014982:Xenopus laevis
D044094:Receptors, Melatonin; D017981:Receptors, Neurotransmitter; D014363:Tryptamines; C057154:luzindole; D008550:Melatonin