P. GovitrapongV. PrapapanichM. EbadiMahidol UniversityUniversity of Nebraska Medical Center, College of Medicine2018-08-102018-08-101991-01-01Journal of Pineal Research. Vol.11, No.3-4 (1991), 182-1871600079X074230982-s2.0-0026357857https://repository.li.mahidol.ac.th/handle/20.500.14594/22001Abstract: The concentration of serotonin in the pineal gland is extremely high, which prompted speculation that in addition to serving as a precursor of melatonin, serotonin may have an independent function of its own. By using [3H]‐spiperone as a ligand, and ketanserine as a selective serotonin 5HT2receptor antagonist, we have identified 5HT2receptor in the bovine pineal gland, revealing a single population of binding sites with a dissociation equilibrium constant (Kd) value of 1.26 ± 0.41 nM and a receptor density (Bmax) value of 193 ± 38.85 fmol/mg protein. In displacement experiments, the concentrations of the drugs required to inhibit 50% of the specific binding of [3H]‐spiperone in descending order of potency were methysergide > ritanserin > pirenperone > pipamperone > ketanserin > cyproheptadine > M‐trifluoromethylphenyl‐piperazine > prazosin > 5‐methoxy‐N‐N‐dimethyltryptamine hydrogen oxalate > 1‐(3‐chlorophenol) piperazine > serotonin. In the rat pineal gland, [3H]‐spiperone revealed a low affinity serotonin binding site with a Kd value of 25.77 ± 10.7 nM and a Bmaxvalue of 1244 ± 472 fmol/mg protein. The results of these studies are interpreted to indicate that the bovine pineal gland possess serotonin 5HT2receptor. However, the rat pineal gland possess a serotoninergic binding site of unknown nature. Copyright © 1991, Wiley Blackwell. All rights reservedMahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1111/j.1600-079X.1991.tb00477.x