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Titolo:
STIMULATION OF PROLACTIN-RELEASE BY DOPAMINE WITHDRAWAL - ROLE OF MEMBRANE HYPERPOLARIZATION
Autore:
GREGERSON KA; GOLESORKHI N; CHUKNYISKA R;
Indirizzi:
UNIV MARYLAND,DEPT PEDIAT,10-039 BRB,655 W BALTIMORE ST BALTIMORE MD 21201 UNIV MARYLAND,CTR STUDIES REPROD,DEPT PHYSIOL BALTIMORE MD 21201
Titolo Testata:
American journal of physiology: endocrinology and metabolism
fascicolo: 5, volume: 30, anno: 1994,
pagine: 781 - 788
SICI:
0193-1849(1994)30:5<781:SOPBDW>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
ANTERIOR-PITUITARY CELLS; RAT LACTOTROPH CELLS; ACTION-POTENTIALS; SECRETION; RECEPTOR; MODULATION; CHANNELS; CURRENTS; HORMONE; BLOOD;
Keywords:
STIMULUS-SECRETION COUPLING; PITUITARY; ELECTROPHYSIOLOGY; PERIFUSION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
31
Recensione:
Indirizzi per estratti:
Citazione:
K.A. Gregerson et al., "STIMULATION OF PROLACTIN-RELEASE BY DOPAMINE WITHDRAWAL - ROLE OF MEMBRANE HYPERPOLARIZATION", American journal of physiology: endocrinology and metabolism, 30(5), 1994, pp. 781-788

Abstract

Hypothalamic dopamine (DA) tonically inhibits prolactin (PRL) releasefrom the anterior pituitary gland, whereas removal of DA markedly augments its release to values exceeding pre-DA rates. We investigated whether electrical events induced by DA contribute to this secretory rebound. In primary cultured lactotropes, spontaneous Ca2+-dependent spiking activity was enhanced after recovery from DA-induced hyperpolarization. Voltage clamp studies showed a rapidly and a slowly inactivatingCa2+ current that were both augmented by a hyperpolarizing conditioning potential. We measured PRL release from perifused cells exposed to DA to correlate the electrical with the secretory responses. DA inhibited PRL release by 67%, whereas PRL secretion increased three- to fourfold over basal release after washout of DA. Valinomycin, used to directly hyperpolarize the cell membrane, mimicked the actions of DA, inhibiting PRL release (65%) and, upon washout, augmenting PRL secretion. Blocking the DA- or valinomycin-induced hyperpolarization by elevatingexternal K+ concentration blocked both the inhibition and rebound of PRL release. These novel results demonstrate that hyperpolarization ofthe lactotrope membrane by DA is critical for the development of PRL rebound after DA withdrawal. We hypothesize the mechanism involves theremoval of inactivation from a population of Ca2+ channels, leading to enhanced Ca2+ influx and PRL release upon recovery of the resting membrane potential after DA removal.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 20/01/20 alle ore 16:18:15