5-Methoxypsoralen enhances plasma melatonin concentrations in the male rat: non-noradrenergic-mediated stimulation and lack of effect in pinealectomized animals.
Previous studies have shown that 8-methoxypsoralen (8-MOP) is able to enhance melatonin secretion from rat pineal glands. The effect of another psoralen, 5-methoxypsoralen (5-MOP) on plasma melatonin concentrations alone or in combination with isoproterenol (Iso, 10 mg/kg BW, i.p.) or propranolol (Prop, 20 mg/kg BW, s.c.) was studied in the rat. An increase in plasma melatonin concentrations was observed 1 h after psoralen administration and lasted 8 h. The stimulatory effect of 5-MOP on circulating melatonin concentrations was dose dependent above 5-mg/kg, BW. 5-MOP also potentiated the Iso-induced rise in plasma melatonin levels. Furthermore, Prop did not block the effect of 5-MOP, indicating that the psoralen acts independently of the noradrenergic system controlling pineal melatonin synthesis. No increase in plasma melatonin levels was observed in pinealectomized (Px) animals after injection of 5-MOP (20 mg/kg BW) or 8-MOP (20 mg/kg BW). This demonstrates that the rise in plasma melatonin concentrations observed after treatment requires the presence of the pineal gland, and that neither 5-MOP nor 8-MOP stimulates melatonin release from other structures such as the retina or Harderian gland.
Mauviard
F
F
Neurobiologie des fonctions rythmiques et saisonnières, Université Louis Pasteur, Strasbourg, France.
Pévet
P
P
Forlot
P
P
D000078223:5-Methoxypsoralen; D000704:Analysis of Variance; D000818:Animals; D004305:Dose-Response Relationship, Drug; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008550:Melatonin / Q000097:blood*; D008730:Methoxsalen / Q000031:analogs & derivatives* / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology*; D010870:Pineal Gland / Q000187:drug effects* / Q000601:surgery; D011433:Propranolol / Q000494:pharmacology; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D000078223:5-Methoxypsoralen; D011433:Propranolol; D008550:Melatonin; D007545:Isoproterenol; D008730:Methoxsalen; D009638:Norepinephrine