Serotonin release mechanisms in bovine pineal gland: stimulation by norepinephrine and dopamine.
An assessment of serotonin (5HT) release was made in bovine pineal gland. Bovine pineal fragments took up [3H]5HT by a Na+-dependent process exhibiting two apparent Km, i.e. a high affinity uptake system (Km = 220 nM) and a low affinity uptake system (Km = 197 microM). A significant release of [3H]5HT was elicited by increasing K+ concentrations in the medium (20-80 mM). Exposure of bovine pineal fragments to varying doses of catecholaminergic agonists indicated that a significant [3H]5HT release was elicited at the following threshold concentrations: 10(-6) M norepinephrine (NE), 10(-7) M dopamine (DA), 10(-6) phenylephrine and 10(-6) M isoproterenol. By employing specific receptor agonists and antagonists, the 5HT release activity of adrenergic agonists was found to be mediated by alpha 1-adrenoceptors, while that of DA by D2-dopaminergic receptors. 5HT release elicited by NE or DA, as well as that by 30 mM K+, was Ca2+-dependent. Both NE and DA increase 45Ca2+ uptake in a dispersed cell preparation of bovine pineal glands. As in the case of 5HT release, the effect of NE and DA on calcium uptake was mediated by alpha 1-adrenoceptors and D2-dopaminergic receptors, respectively. These results indicate that both NE and DA control 5HT release in bovine pineal gland.
Chuluyan
H E
HE
Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Rosenstein
R E
RE
Cardinali
D P
DP
D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D003000:Clonidine / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D018492:Dopamine Antagonists; D006220:Haloperidol / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009638:Norepinephrine / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011224:Prazosin / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism* / Q000502:physiology; D013469:Sulpiride / Q000494:pharmacology
D001552:Benzazepines; D018492:Dopamine Antagonists; D010656:Phenylephrine; D012701:Serotonin; D013469:Sulpiride; D011433:Propranolol; D006220:Haloperidol; D007545:Isoproterenol; D003000:Clonidine; D002118:Calcium; D004298:Dopamine; D009638:Norepinephrine; D011224:Prazosin; D010646:Phentolamine