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Titolo:
ELECTROPHYSIOLOGICAL EFFECTS OF ALPHA(2)-ADRENERGIC STIMULATION IN CANINE CARDIAC PURKINJE-FIBERS
Autore:
SAMSON RA; CAI JJ; SHIBATA EF; MARTINS JB; LEE HC;
Indirizzi:
UNIV IOWA HOSP & CLIN,DEPT INTERNAL MED,DIV CARDIOVASC IOWA CITY IA 52242 UNIV IOWA,COLL MED,DEPT PEDIAT,DIV PEDIAT CARDIOL IOWA CITY IA 52242 UNIV IOWA,COLL MED,DEPT PHYSIOL & BIOPHYS IOWA CITY IA 52242 UNIV IOWA,COLL MED,DEPT INTERNAL MED,DIV CARDIOVASC IOWA CITY IA 52242
Titolo Testata:
American journal of physiology. Heart and circulatory physiology
fascicolo: 5, volume: 37, anno: 1995,
pagine: 2024 - 2035
SICI:
0363-6135(1995)37:5<2024:EEOASI>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
VASCULAR SMOOTH-MUSCLE; PERTUSSIS-TOXIN; DELAYED AFTERDEPOLARIZATIONS; ALPHA-ADRENOCEPTORS; TRIGGERED ACTIVITY; SIMULATED ISCHEMIA; ADENYLATE-CYCLASE; G-PROTEINS; RECEPTOR; BINDING;
Keywords:
ALPHA(2)-ADRENERGIC RECEPTOR; ACTION POTENTIAL DURATION; DELAYED AFTERDEPOLARIZATION; G PROTEIN; UK-14304;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
39
Recensione:
Indirizzi per estratti:
Citazione:
R.A. Samson et al., "ELECTROPHYSIOLOGICAL EFFECTS OF ALPHA(2)-ADRENERGIC STIMULATION IN CANINE CARDIAC PURKINJE-FIBERS", American journal of physiology. Heart and circulatory physiology, 37(5), 1995, pp. 2024-2035

Abstract

The effects of alpha(2)-adrenergic stimulation on action potentials were measured in isolated canine Purkinje fibers. Action potential durations at 50 and 90% of repolarization (APD(50) and APD(90)) were significantly prolonged by 0.25 mu M l-norepinephrine + 0.5 mu M dl-propranolol (NE + P) from baseline values of 166 +/- 7 and 249 +/- 9 (SE) ms (n = 7) to 174 +/- 7 and 265 +/- 9 ms, respectively (P < 0.05 for both). Selective alpha(2)-blockade with 0.01 mu M yohimbine (YO) reduced this prolongation by NE + P in APD(50) and APD(90) to 169 +/- 7 and 256+/- 8 ms, respectively (P < 0.05 compared with NE + P). Additional selective alpha(1)-blockade with 0.01 mu M prazosin (PZ) completely blocked the effects of NE + P, returning APD(50) and APD(90) to 163 +/- 7 and 250 +/- 9 ms (not different from baseline). After incubation of isolated Purkinje fibers with pertussis toxin (1 mu g/ml), which reducedthe availability of a 41-kDa membrane protein for ADP ribosylation by70 +/- 7% (n = 4, P < 0.05), YO failed to reverse the prolongation inaction potential durations brought on by NE + P, but the effects of PZ were intact. The effects of alpha(2)-stimulation on beta-adrenergic-induced delayed afterdepolarizations (DADs) were studied by burst pacing of Purkinje fibers in Tyrode solution containing 7.5 mM Ca2+. The DADs induced in the presence of NE + PZ (beta- + alpha(2)-stimulation) were significantly smaller in amplitude and required a shorter pacing cycle length to reach threshold than those induced in the presence of NE + PZ + YO (unopposed beta-adrenergic stimulation). Furthermore sustained triggered activity, seen in five of eight preparations under beta-stimulation, could no longer be elicited in the presence of beta- + alpha(2)-stimulation. These results suggest that the postjunctional alpha(2)-adrenergic receptors in canine Purkinje fibers are coupled to apertussis toxin-sensitive G protein and that stimulation of these receptors leads to action potential prolongation and suppression of DADs induced by beta-adrenergic stimulation.

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Documento generato il 29/11/20 alle ore 16:02:15