title: Circadian rhythms of plasma melatonin in the ruin lizard Podarcis sicula: effects of pinealectomy.
abstract: Plasma melatonin was measured in lizards (Podarcis sicula) at six different times of day under conditions of constant temperature and darkness. Intact animals showed a circadian rhythm of melatonin with a peak in the subjective night of 207 pg/ml (median) and a trough during the subjective day that was below the minimum detection level of the assay (50 pg/ml). Pinealectomy abolished the circadian rhythm of plasma melatonin; median levels were near or below the minimum detection level at all times sampled. The data suggest that the pineal is the only source of rhythmic blood-borne melatonin in Podarcis sicula, and are consistent with the hypothesis that changes in the free-running period of the locomotor rhythm induced by pinealectomy in this species are due to withdrawal of rhythmic melatonin from the blood.
authors.affiliation: Dipartimento di Scienze del Comportamento Animale e dell'Uomo Pisa, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Foà
authors.forename: D
authors.initials: D
authors.lastname: Janik
authors.forename: L
authors.initials: L
authors.lastname: Minutini
mesh_terms: D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D003623:Dark Adaptation; D008027:Light; D008116:Lizards; D008297:Male; D008550:Melatonin / Q000097:blood*; D010870:Pineal Gland / Q000502:physiology* / Q000601:surgery; D011863:Radioimmunoassay; D012160:Retina / Q000502:physiology
chemical_list: D008550:Melatonin