神经递质对豚鼠左心室流出道自律细胞电活动的影响

为研究左心室流出道慢反应自律细胞的神经支配和受体分布,本实验采用标准玻璃微电极细胞内记录技术,分别观测了肾上腺素能和胆碱能受体激动剂及相应的受体拮抗剂对离体豚鼠左心室流出道组织自发慢反应电位的影响。观测指标有：最大舒张电位（maximal diastolic potential,MDP）、动作电位幅度（amplitude of action potential,APA）、0相最大去极速度（maximal rate of depolarization,Vmax）、4相自动去极速度（velocity of diastolic depolarization,VDD）、复极50％时间（50％of duration of action potential,APD50）和90％时间（90％ of duration of action potential,APD50）以及自发放电频率（rate of pacemaker firing,RPF）。结果表明：（1）100μmol／L异丙肾上腺素（isoprenaline,Iso）可使RPF和VDD显著加快（P〈0．01）,MDP绝对值和APA显著增大（P〈0．05,P〈0．01）,Vmax加快（P〈0．05）,APD50缩短（P〈0．01）,这些变化均可被5μmol／L心得安拮抗;（2）100μmol／L肾上腺素（epinephrine,E）可使RPF和VDD加快（P＜0．01,P〈0．05）,APA显著增大（P〈0．001）,Vmax加快（P〈0．05）,APD50和APD90缩短（P＜0．05）;（3）100μmol／L去甲肾上腺素（norepinephrine,NE）可使VDD和RPF加快（P＜0．05）,APA显著增大（P〈0．05）,Vmax明显加快（P〈0．05）,APD50缩短（P〈0．05）,这些变化可被100μmol／L酚妥拉明拮抗;（4）10μmol／L ACh可使VDD和RPF减慢（P〈0．05）,APA显著减小（P〈0．01）,APD50缩短（P〈0．05）;ACh对APD50的缩短效应可被10μmol／L阿托品拮抗（P〈0．05）。结果提示：左心室流出道自律细胞膜上可能存在α-肾上腺素能受体（α-adrenergic receptor,α-AR、β-肾上腺素能受体（β-adrenergic receptor,β-AR）以及M型胆碱能受体（muscarinic receptor,MR）,其自律性电活动可能也接受心交感神经和心迷走神经调控。

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

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 mumol/L isoprenaline (Iso) resulted in a significant increase in V(max) (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 mumol/L), propranolol (5 mumol/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 mumol/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 mumol/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 mumol/L), phentolamine (100 mumol/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 mmol/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), APD50 shortened markedly (P<0.05), Atropine (10 mmol/L) antagonized the effects of ACh (10 mumol/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.