Localization and characterization of melatonin receptors in the rabbit spinal cord.
Melatonin receptors in the rabbit spinal cord were studied. Using in vitro quantitative autoradiography we have localized and characterized 2-[125I]iodomelatonin ([125I]MEL) binding sites in the central gray substance (lamina X) of the rabbit spinal cord. Saturation study revealed a single class of high affinity binding sites in the central gray substance with an equilibrium dissociation constant (Kd) of 38.8 +/- 5.25 pM and a maximum number of binding sites of 5.69 +/- 0.84 fmol/mg protein in the mid-light period. These [125I]MEL binding sites were highly specific for melatonin. Coincubation with 10 microM or 50 microM guanosine 5'-O-(3-thiotriphosphate) produced a significant change in Kd. These results suggest that melatonin receptors in the rabbit spinal cord are coupled to a guanine-nucleotide-binding protein (G-protein). Our studies suggest that melatonin exerts a direct action on the rabbit spinal cord.
Wan
Q
Q
Department of Physiology, University of Hong Kong.
Liao
M
M
Brown
G M
GM
Pang
S F
SF
D000818:Animals; D001345:Autoradiography; D019204:GTP-Binding Proteins / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007457:Iodine Radioisotopes; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives / Q000378:metabolism / Q000493:pharmacokinetics; D011817:Rabbits; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D044094:Receptors, Melatonin; D013116:Spinal Cord / Q000033:anatomy & histology* / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D018160:Receptors, Cytoplasmic and Nuclear; D044094:Receptors, Melatonin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C044556:2-iodomelatonin; D019204:GTP-Binding Proteins; D008550:Melatonin