Effects of melatonin on 2-deoxy-[1-14C]glucose uptake within rat suprachiasmatic nucleus.
Previously, we have demonstrated that metabolic activity, shown by autoradiographic determination of 2-deoxy-[1-14C]glucose (2-DG) uptake, within the rat hypothalamic suprachiasmatic nuclei (SCN) was inhibited by subcutaneous injection of 1 mg/kg melatonin. To determine whether this effect was specific to a particular time of day, the effects of melatonin on 2-DG uptake were studied in several hypothalamic areas, including the SCN, supraoptic nuclei (SON), lateral hypothalamic area (LHA), and anterior hypothalamic area (AHA) every 4 h throughout the circadian day. In a second experiment, the effects of different melatonin doses were studied at the time of day at which melatonin had its maximal effect to determine the dose-response relationship of melatonin-induced inhibition of SCN 2-DG uptake. The data indicate that melatonin inhibited 2-DG uptake in the SCN alone at one time of day, primarily at circadian time (CT) 6 and CT10, 2-6 h before subjective dusk, and secondarily at CT22, just before subjective dawn. This effect was dose dependent with a 50% effective dose of 1.49 +/- 2.30 micrograms/kg. The temporal and dose-response characteristics of these effects are similar to those characterizing the entraining effects of melatonin on circadian patterns of locomotion and drinking.
Cassone
V M
VM
Department of Neurology, State University of New York, Stony Brook 11794-8121.
Roberts
M H
MH
Moore
R Y
RY
D000818:Animals; D001345:Autoradiography; D001693:Biological Transport, Active / Q000187:drug effects; D002250:Carbon Radioisotopes; D002940:Circadian Rhythm; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D051381:Rats; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism*
D002250:Carbon Radioisotopes; D003837:Deoxy Sugars; D003847:Deoxyglucose; D008550:Melatonin