title: Identification and functional significance of nicotinic cholinergic receptors in the rat pineal gland.
abstract: The existence and subunit identification of the nicotinic cholinergic receptors in the rat pineal gland were examined by autoradiography, using [3H]cytisine and [125I]alpha-bungarotoxin as labelled ligands. The experiments performed with radioactive cytisine did not reveal specific binding, while iodinated alpha-bungarotoxin disclosed moderate specific binding density, suggesting that the nicotinic cholinergic receptor in the rat pineal is structurally organized with the alpha 7 or alpha 8 subunits present, the only ones that bind alpha-bungarotoxin with high affinity. In vitro functional experiments using pineal explants demonstrated that the binding site may represent a readily accessible nicotinic cholinergic receptor. Nicotine, though having no effect per se on the synthesis and release of melatonin, significantly diminished, in a dose-dependent manner, the norepinephrine-stimulated melatonin accumulation. This effect could be blocked by coincubation with the cholinergic antagonist d-tubocurarine, suggesting that the nicotinic cholinergic receptor in the rat pineal could be involved in the functional regulation of the gland.
authors.affiliation: Department of Pharmacology, University of Milan, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Stankov
authors.forename: M
authors.initials: M
authors.lastname: Cimino
authors.forename: P
authors.initials: P
authors.lastname: Marini
authors.forename: V
authors.initials: V
authors.lastname: Lucini
authors.forename: F
authors.initials: F
authors.lastname: Fraschini
authors.forename: F
authors.initials: F
authors.lastname: Clementi
mesh_terms: D000470:Alkaloids / Q000378:metabolism; D000818:Animals; D001392:Azocines; D002038:Bungarotoxins / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D009538:Nicotine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology*; D009924:Organ Culture Techniques; D010870:Pineal Gland / Q000378:metabolism*; D011807:Quinolizines; D051381:Rats; D017207:Rats, Sprague-Dawley; D011978:Receptors, Nicotinic / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D012016:Reference Values; D012741:Sexual Maturation; D014403:Tubocurarine / Q000494:pharmacology*; D000093843:Quinolizidine Alkaloids
chemical_list: D000470:Alkaloids; D001392:Azocines; D002038:Bungarotoxins; D007457:Iodine Radioisotopes; D008550:Melatonin; D009538:Nicotine; D009638:Norepinephrine; D011807:Quinolizines; D011978:Receptors, Nicotinic; D014403:Tubocurarine; C004712:cytisine; D000093843:Quinolizidine Alkaloids