- 作者: Mario Vassalle; John N Catanzaro; Michael P Nett; Marcello Rota
- 作者服務機構: Department of Physiology and Pharmacology, Box 31, State University of New York, Downstate Medical Center, NY, USA.
- 中文摘要: --
- 英文摘要:
Background :
The diastolic oscillatory after-potential Vos and pre-potential ThVos play an essential role in the
pacemaker mechanism of sino-atrial node (SAN). The aim of this study was to investigate
whether these oscillatory potentials are also involved in adrenergic control of SAN discharge.
Methods :
Vos and ThVos were visualized by superfusing guinea pig SAN in high [K+]o. The actions of
adrenergic agonists on oscillatory potentials were studied by means of a microelectrode
technique. Statistical significance was determined by means of Student's paired t-test.
Results :
In non-spontaneous SAN, norepinephrine (NE) decreased the resting potential into a voltage
range (“oscillatory zone”) where increasingly larger ThVos appeared and initiated spontaneous
discharge. In slowly discharging SAN, NE gradually increased the rate by increasing the
amplitude and slope of earlier-occurring ThVos and of Vos until these oscillations fused with
initial diastolic depolarization (DD1). In the presence of NE, sudden fast rhythms were initiated
by large Vos that entered a more negative oscillatory zone and initiated a large ThVos. Recovery
from NE exposure involved the converse changes. The ß-adrenergic agonist isoproterenol had
similar actions. Increasing calcium load by decreasing high [K+]o, by fast drive or by recovery in
Tyrode solution led to growth of Vos and ThVos which abruptly fused when a fast sudden rhythm
was induced. Low [Ca2+]o antagonized the adrenergic actions. Cesium (a blocker of If) induced
spontaneous discharge in quiescent SAN through ThVos. In spontaneous SAN, Cs+
increased Vos
and ThVos, thereby increasing the rate. Cs+ did not hinder the positive chronotropic action of NE.
Barium increased the rate, as Cs+ did. - 中文關鍵字: --
- 英文關鍵字: --