赛庚啶对豚鼠乳头状肌的收缩性与动作电位的影响

Cyp对豚鼠孔头状肌有浓度依赖性负性肌力作用,提高浴液钙浓度此作用减弱,对高K~+除极后ISO恢复的收缩抑制作用更强。较高浓度的Cyp使频率依赖性正阶梯现象取消和翻转。对乳头状肌AP,Cyp浓度依赖性地使APD_(20),APD_(50),APD_(90)和ERP缩短。灌流液中Ca~(2+)降低或升高分别使该作用增强或减弱,K~+的改变对其作用影响较小。提示Cyp对豚鼠乳头状肌收缩性和AP的作用可能主要是抑制心肌跨膜Ca~(2+)内流所致。

Effects of cyproheptadine on contractility and action potential of guinea pig papillary muscles

It was found that the effects of cle was a concentration-dependent negatively cyproheptadjne (Cyp) on the guinea pig papillary mus- inotropic action. With the increase of Ca2+]0 from 1.8 to 3.6 mmol/ L, this action was decreased (IC50 = 4.4 and 12.4 μmol/ L, respectively). In the contractile response restored by Iso in guinea pig papillary muscles depolarized by high potassium, Cyp showed more markedly depressant effect (IC50 = 0.53 μmol/ L). Cyp 32 μmol/L and Ver 0.8 μmol/L abolished and reversed the frequency-dependent positive staircase phenomenon to the negative one. Conventional microelectrode techniques were used to determine the effects of Cyp on the action potentials of guinea pig papillary muscles. The effects of Cyp (2-32 μmol / L) on action potential showed a shortening of the action potential duration (APD20, APD50, APD90) and the ef-fective refractory period (ERP) in a concentration-dependent manner. Cyp-induced shortening in APD was attenuated or slightly enhanced by the increased or decreased Ca2+]0 respectively. But the effects of changes in K+]0 on the Cyp-induced shortening in APD were minor. The results suggest that the Cyp-induced shortening in APD and the decrement of contractile response may be primarily due to a blockade of slow calcium influx.