Issue Archive

Electrophysiological effects of neurotransmitters on pacemaker cells in guinea pig left ventricular outflow tract

Zhao Lanping, Zhang Xiaoyun, Chen Yanjing, Li Jiandong, Zhang Sanming, Wang Xuefang, Ge Fugui

Department of Physiology, Hebei North University.Zhangjiakou 075000,Hebei

Abstract

This study was designed to explore the innervation of autonomic nervous system and the distribution of receptors on pacemaker cell membrane in guinea pig left ventricular outflow tract (aortic vestibule). By using conventional intracellular microelectrode technique to record action potentials, autonomic neurotransmitters and antagonists were used to investigate the electrophysiological features and regularities of spontaneous activity of left ventricular outflow tract cells. Electrophysiological parameters examined were: maximal diastolic potential (MDP), amplitude of action potential (APA), maximal rate of depolarization (V_(max)), velocity of diastolic depolarization (VDD), rate of pacemaker firing (RPF), 50% and 90% of duration of action potential (APD_(50) and APD_(90)). The results are listed below: (1) Perfusion with 100 #mu#mol/L isoprenaline (Iso) resulted in a significant increase in Vmax (P<0.05), VDD, RPF, and APA (P<0.01), a notable decrease in MDP (P<0.05), and also a marked shortening in APD_(50) (P<0.01). Pretreatment with Iso (100 #mu#mol/L), propranolol (5 mmol/L) significantly decreased RPF and VDD (P<0.01), decreased APA, MDP and V_(max) (P<0.01) notably, prolonged APD_(50) (P<0.01) and APD_(90) (P<0.05) markedly. (2) Application of 100 #mu#mol/L epinephrine (E) resulted in a significant increase in VDD (P<0.05), RPF (P<0.001), V_(max) (P<0.05) and APA (P<0.001), and a notable shortening in APD_(50) and APD_(90) (P<0.05). (3) Perfusion with 100 #mu#mol/L norepinephrine (NE) led to a significant increase in VDD, RPF，APA and V_(max) (P<0.05), and a marked shortening in APD_(50) (P<0.05). Pretreatment with NE (100 #mu#mol/L), phentolamine (100 #mu#mol/L) significantly decreased RPF and VDD, MDP and APA (P<0.01), decreased V_(max) notably (P<0.05), prolonged APD_(50) and APD_(90) markedly (P<0.01).(4) During perfusion with 10 #mu#mol/L acetylcholine (ACh), VDD and RPF slowed down notably (P<0.05), APA decreased significantly (P<0.001), V_(max) slowed down notably (P<0.01),APD_(50) shortened markedly (P<0.05), Atropine (10 #mu#mol/L) antagonized the effects of ACh (10 #mu#mol/L) on APD_(50) (P<0.05). These results suggest that there are probably #alpha#-adrenergic reecptor (#alpha#-AR), #beta#-adrenergic receptor (#beta#-AR) and muscarinic receptor (MR) on pacemaker cell membrane of left ventricular outflow tract in guinea pig. The spontaneous activities of left ventricular outflow tract cells are likely regulated by sympathetic and parasympathetic nerves.

Key words: Neurotransmitters;Guinea pig;ventricular outflow;electrophysiology

Received: 　　Accepted:

Corresponding author: 　　E-mail:

Citing This Article：

Zhao Lanping, Zhang Xiaoyun, Chen Yanjing, Li Jiandong, Zhang Sanming, Wang Xuefang, Ge Fugui. Electrophysiological effects of neurotransmitters on pacemaker cells in guinea pig left ventricular outflow tract . Acta Physiol Sin 2005; 57 (5): (in Chinese with English abstract).