Jb. Zawilska et Jz. Nowak, CHARACTERIZATION OF MELATONIN RECEPTORS IN THE BRAIN OF 4 AVIAN SPECIES - DUCK, GOOSE, PIGEON, AND TURKEY, General and comparative endocrinology, 101(2), 1996, pp. 227-234
Melatonin receptor sites were characterized in the brains of four avia
n species (duck, goose, pigeon, and turkey) by an in vitro binding tec
hnique, using 2-[I-125]iodomelatonin as a labeled ligand. The specific
binding of 2-[I-125]iodomelatonin to avian brain membranes was found
to be stable, saturable, reversible, and of high affinity. Scatchard a
nalysis revealed that 2-[I-125]iodomelatonin binds to a single class o
f sites in brain membrane preparations of these species with high affi
nity (affinity constants K-d between 153 and 289 pM) and low capacity
(total number of binding sites B-max between 5.07 and 10.15 fmol/mg pr
otein). Competition studies showed the following relative order of pot
ency of indolic compounds to inhibit the specific 2-[I-125]iodomelaton
in binding: melatonin >> N-acetyltryptamine> > N-acetyl-5-hydroxytrypt
amine > 5-hydroxytryptamine >>> 5-methoxytryptamine. We conclude that
the 2-[I-125]iodomelatonin-binding sites in brains of duck, goose, pig
eon, and turkey have similar binding and pharmacological characteristi
cs, and may represent ML-1 melatonin receptor sites. (C) 1996 Academic
Press, Inc.