Abstract
We studied the ability of α-adrenergic stimulation to induce delayed afterdepolarizations and triggered activity in Purkinje fibers from cat hearts in the presence of an elevated Ca++ concentration. Delayed afterdepolarizations could not be induced at drive cycle lengths of 200 to 500 msec in the presence of extracellular Ca++ concentrations of 2.7 to 8.1 mM. However, the addition of 10-5M phenylephrine in the presence of 5 x 10-7M propranolol elicited delayed afterdepolarizations in eight of 10 preparations at a Ca++ concentration of 8.1 mM; nondrive-triggered action potentials were recorded from three of the preparations. These afterpotentials were completely suppressed by 5 x 10-7M prazosin or 10-6M phentolamine. In the presence of 5 x 10-7M propranolol, 10-5M phenylephrine prolonged action potential duration and this effect was suppressed by 5 x 10-7M prazosin. Methoxamine, at a concentration of 5 x 10-6M, was also observed to potentiate delayed afterdepolarizations in all of three preparations studied. These results demonstrate that α-adrenergic stimulation can induce afterpotentials in the presence of elevated Ca++ levels in cat hearts. Stimulation of α-adrenoceptors may be responsible for arrhythmias under Ca++-loaded conditions such as ischemia and coronary reperfusion.
| Original language | English |
|---|---|
| Pages (from-to) | 1074-1082 |
| Number of pages | 9 |
| Journal | Circulation |
| Volume | 70 |
| Issue number | 6 |
| State | Published - Dec 1 1984 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Physiology
- Cardiology and Cardiovascular Medicine
Cite this
Delayed afterdepolarizations and triggered activity induced in feline Purkinje fibers by α-adrenergic stimulation in the presence of elevated calcium levels. / Kimura, S.; Cameron, J. S.; Kozlovskis, P. L.; Bassett, A. L.; Myerburg, Robert J.
In: Circulation, Vol. 70, No. 6, 01.12.1984, p. 1074-1082.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Delayed afterdepolarizations and triggered activity induced in feline Purkinje fibers by α-adrenergic stimulation in the presence of elevated calcium levels
AU - Kimura, S.
AU - Cameron, J. S.
AU - Kozlovskis, P. L.
AU - Bassett, A. L.
AU - Myerburg, Robert J
PY - 1984/12/1
Y1 - 1984/12/1
N2 - We studied the ability of α-adrenergic stimulation to induce delayed afterdepolarizations and triggered activity in Purkinje fibers from cat hearts in the presence of an elevated Ca++ concentration. Delayed afterdepolarizations could not be induced at drive cycle lengths of 200 to 500 msec in the presence of extracellular Ca++ concentrations of 2.7 to 8.1 mM. However, the addition of 10-5M phenylephrine in the presence of 5 x 10-7M propranolol elicited delayed afterdepolarizations in eight of 10 preparations at a Ca++ concentration of 8.1 mM; nondrive-triggered action potentials were recorded from three of the preparations. These afterpotentials were completely suppressed by 5 x 10-7M prazosin or 10-6M phentolamine. In the presence of 5 x 10-7M propranolol, 10-5M phenylephrine prolonged action potential duration and this effect was suppressed by 5 x 10-7M prazosin. Methoxamine, at a concentration of 5 x 10-6M, was also observed to potentiate delayed afterdepolarizations in all of three preparations studied. These results demonstrate that α-adrenergic stimulation can induce afterpotentials in the presence of elevated Ca++ levels in cat hearts. Stimulation of α-adrenoceptors may be responsible for arrhythmias under Ca++-loaded conditions such as ischemia and coronary reperfusion.
AB - We studied the ability of α-adrenergic stimulation to induce delayed afterdepolarizations and triggered activity in Purkinje fibers from cat hearts in the presence of an elevated Ca++ concentration. Delayed afterdepolarizations could not be induced at drive cycle lengths of 200 to 500 msec in the presence of extracellular Ca++ concentrations of 2.7 to 8.1 mM. However, the addition of 10-5M phenylephrine in the presence of 5 x 10-7M propranolol elicited delayed afterdepolarizations in eight of 10 preparations at a Ca++ concentration of 8.1 mM; nondrive-triggered action potentials were recorded from three of the preparations. These afterpotentials were completely suppressed by 5 x 10-7M prazosin or 10-6M phentolamine. In the presence of 5 x 10-7M propranolol, 10-5M phenylephrine prolonged action potential duration and this effect was suppressed by 5 x 10-7M prazosin. Methoxamine, at a concentration of 5 x 10-6M, was also observed to potentiate delayed afterdepolarizations in all of three preparations studied. These results demonstrate that α-adrenergic stimulation can induce afterpotentials in the presence of elevated Ca++ levels in cat hearts. Stimulation of α-adrenoceptors may be responsible for arrhythmias under Ca++-loaded conditions such as ischemia and coronary reperfusion.
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M3 - Article
VL - 70
SP - 1074
EP - 1082
JO - Circulation
JF - Circulation
SN - 0009-7322
IS - 6
ER -