Effect of pinealectomy and the light/dark cycle on 2-[125I]iodomelatonin binding in the chick optic tectum.
1. These studies investigated the regulation of melatonin receptor sites within the chick brain by the light/dark cycle and by endogenous melatonin using quantitative autoradiography. Saturation analyses performed in coronal brain sections of the optic tectum revealed a single class of high-affinity binding sites. 2. For diurnal rhythm studies, chicks were maintained on a 14:10 L:D cycle (light on 0400) and sacrificed at 4-h intervals. No significant variation was observed in either the affinity (KD = 67.8-76.4 pM) or the density (BMAX = 88.9-118.9 fmol/mg protein) of 2-[125I]iodomelatonin binding sites as a function of time of day. 3. In pinealectomized or age-matched sham-operated chicks, no changes were found in either the affinity (KD = 66.7-89.1 pM) or the density (BMAX = 112.8-180.4 fmol/mg protein) of 2-[125I]iodomelatonin binding sites at either 1, 7, or 14 days following surgery. These data suggest that endogenous pineal melatonin may not play a role in the regulation of melatonin receptor site affinity or density in the chick optic tectum.
Siuciak
J A
JA
Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois 60611.
Dubocovich
M L
ML
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism*; D002645:Chickens / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D015536:Down-Regulation / Q000528:radiation effects; D008027:Light; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism*; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery; D011956:Receptors, Cell Surface / Q000378:metabolism*; D044094:Receptors, Melatonin; D013045:Species Specificity; D013477:Superior Colliculi / Q000378:metabolism*; D015854:Up-Regulation / Q000528:radiation effects
D011956:Receptors, Cell Surface; D044094:Receptors, Melatonin; D008550:Melatonin