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Titolo:
VOLTAGE-DEPENDENT CALCIUM CURRENTS IN BULBOSPINAL NEURONS OF NEONATALRAT ROSTRAL VENTROLATERAL MEDULLA - MODULATION BY ALPHA(2)-ADRENERGICRECEPTORS
Autore:
LI YW; GUYENET PG; BAYLISS DA;
Indirizzi:
UNIV VIRGINIA,DEPT PHARMACOL,BOX 448,5017 JORDAN HALL CHARLOTTESVILLEVA 22908 UNIV VIRGINIA,DEPT PHARMACOL CHARLOTTESVILLE VA 22908
Titolo Testata:
Journal of neurophysiology
fascicolo: 2, volume: 79, anno: 1998,
pagine: 583 - 594
SICI:
0022-3077(1998)79:2<583:VCCIBN>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
DORSAL RAPHE NEURONS; POTENTIAL WAVE-FORMS; SPINAL-CORD; HYPOGLOSSAL MOTONEURONS; SYMPATHETIC NEURONS; CATECHOL METABOLISM; PYRAMIDAL NEURONS; CA2+ CHANNELS; INHIBITION; NOREPINEPHRINE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
47
Recensione:
Indirizzi per estratti:
Citazione:
Y.W. Li et al., "VOLTAGE-DEPENDENT CALCIUM CURRENTS IN BULBOSPINAL NEURONS OF NEONATALRAT ROSTRAL VENTROLATERAL MEDULLA - MODULATION BY ALPHA(2)-ADRENERGICRECEPTORS", Journal of neurophysiology, 79(2), 1998, pp. 583-594

Abstract

The properties and modulation by norepinephrine (NE) of voltage-dependent calcium currents were studied in bulbospinal neurons (n = 116) ofthe rostral ventrolateral medulla (RVLM) using whole cell patch-clamptechniques in neonatal rat brain stem slices. RVLM bulbospinal neurons were identified visually by their location in slices and by the presence of flourescein isothiocyanate-tagged microbeads, which were injected into the spinal cord before the experiment; RVLM neurons were filled with Lucifer yellow during recordings, and the slice was processed for detection of tyrosine hydroxylase immunoreactivity (TH-IR). Thirty-four of 42 recovered cells (81%) were positive for TH-IR, indicating that most recorded cells were C1 neurons. Bulbospinal RVLM neurons expressed a prominent high-voltage-activated (HVA) calcium current, whichbegan to activate at -30 to -40 mV (from a holding potential of -60 or -70 mV), and peaked at similar to 0 mV (0.8 +/- 0.1 nA; mean +/- SE). HVA current comprised predominantly omega-conotoxin GVIA-sensitive, N-type and omega-agatoxin NA-sensitive, P/Q-type components, with smaller dihydropyridine-sensitive, L type, and residual current components. Most RVLM bulbospinal neurons (n = 44/52, including 12/14 histologically identified C1 cells) also expressed low-voltage-activated (LVA) calcium current. LVA current began to activate at similar to-60 mV (from a holding potential of -100 mV) and was nearly completely inactivated at -50 mV with a half-inactivation potential of -70 +/- 2 mV. The amplitude of LVA current at -50 mV was 78 +/- 24 pA with Ba2+ and 156 +/- 38 pA with Ca2+ as a charge carrier. NE inhibited HVA current in most bulbospinal RVLM neurons (n = 70/77) with an EC50 of 1.2 mu M; NE had no effect on LVA current. Calcium current inhibition by NE was mediated by alpha(2)-adrenergic receptors (alpha(2)-ARs) as the effect was mimicked by the selective alpha(2)-AR agonist, UK-14,304, and blocked by idazoxan, an alpha(2)-AR antagonist, but unaffected by prazosin andpropranolol (alpha(1)- and beta-AR antagonists, respectively). Most of the NE-sensitive calcium current was N- and P/Q-type. NE-induced inhibition of calcium current evoked by action potential waveforms (APWs)was significantly larger than that evoked by depolarizing steps (34 +/- 2.5 vs. 23 +/- 2.7%; P < 0.05). Although inhibition of calcium current was voltage dependent and partially relieved by strong depolarizations, when calcium currents were evoked with a 10-Hz train of APWs as a voltage command, the inhibitory effect of NE was maintained throughout the train. In conclusion, bulbospinal RVLM neurons, including C1 cells, express multiple types of calcium currents. Inhibition of HVA calcium current by NE may modulate input-output relationships and releaseof transmitters from C1 cells.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 31/03/20 alle ore 22:05:08