Alpha-2 adrenergic activity of bromocriptine and quinpirole in chicken pineal gland. Effects on melatonin synthesis and ( sup 3 H)rauwolscine binding

Journal Article · Sat Dec 01 04:00:00 EST 1990 · Journal of Pharmacology and Experimental Therapeutics; (USA)

OSTI ID:5989159

Zawilska, J; Iuvone, P M ^[1]

---

1. Emory Univ. School of Medicine, Atlanta, GA (USA)

In the pineal gland and retina of chickens, serotonin N-acetyl-transferase (NAT) activity and melatonin content are modulated by different receptors, alpha-2 adrenergic receptors in pineal gland and D2-dopamine receptors in retina. The effect of two D2-dopamine receptor agonists, bromocriptine and quinpirole (LY 171555), on melatonin synthesis in these tissues was investigated. Systemic administrations of bromocriptine and quinpirole decreased nocturnal NAT activity and melatonin content of both pineal gland and retina. Bromocriptine was equipotent in the two tissues, whereas quinpirole was approximately 100-fold more potent in retina than in pineal gland. In pineal gland, the suppressive effects of bromocriptine and quinpirole on NAT activity were blocked by yohimbine, a selective alpha-2 adrenergic receptor antagonist, but not by spiperone, a D2-dopamine receptor antagonist. In contrast, bromocriptine- and quinpirole-induced decreases of the enzyme activity in retina were antagonized by spiperone, and not affected by yohimbine. The nocturnal increase of NAT activity of pineal glands in vitro was inhibited with an order of potency clonidine greater than bromocriptine greater than quinpirole. Additionally, bromocriptine and quinpirole displaced the specific binding of (3H)rauwolscine, an alpha-2 adrenergic receptor antagonist, to membranes from chicken pineal gland, with potencies comparable to those observed for inhibition of NAT activity in vitro. It is suggested that bromocriptine and quinpirole, in addition to their D2-dopaminergic activity, can stimulate alpha-2 adrenergic receptors in pineal gland of chicken.

• OSTI ID: 5989159
• Journal Information: Journal of Pharmacology and Experimental Therapeutics; (USA), Journal Name: Journal of Pharmacology and Experimental Therapeutics; (USA) Vol. 255:3; ISSN 0022-3565; ISSN JPETA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINES
ANIMALS
AROMATICS
AUTONOMIC NERVOUS SYSTEM AGENTS
AZAARENES
AZOLES
BIOCHEMICAL REACTION KINETICS
BIOSYNTHESIS
BIRDS
BODY
BODY AREAS
CARDIOTONICS
CARDIOVASCULAR AGENTS
CELL CONSTITUENTS
CELL MEMBRANES
CHICKENS
DOPAMINE
DRUGS
ENZYME ACTIVITY
ENZYMES
EYES
FACE
FOWL
GLANDS
HEAD
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
INDOLES
ISOTOPE APPLICATIONS
KINETICS
MELATONIN
MEMBRANE PROTEINS
MEMBRANES
NEUROREGULATORS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANS
PHENOLS
PINEAL GLAND
POLYPHENOLS
PROTEINS
PYRROLES
REACTION KINETICS
RECEPTORS
RETINA
SENSE ORGANS
SPIPERONE
SYMPATHOLYTICS
SYMPATHOMIMETICS
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
TRITIUM COMPOUNDS
TRYPTAMINES
VERTEBRATES