敌敌畏对大鼠膈肌的直接毒性作用

Direct toxicity of dichlorvos on isolated rat diaphragm

目的 观察敌敌畏是否对膈肌具有直接抑制作用。方法 用自制双功能电极剌激膈神经或直接剌激离体大鼠膈肌 ,引起膈肌收缩 ,观察农药敌敌畏对膈肌的直接抑制作用。用箭毒阻断神经肌肉接头后 ,剌激膈神经不再引起膈肌收缩 ,直接刺激膈肌引起的收缩与神经肌肉接头无关 ,对这种收缩的影响为对膈肌的直接作用。结果 10V直接刺激膈肌出现类似于强直收缩的波形。敌敌畏浓度大于1.4 5mmol·L- 1时可使该收缩显著抑制 ,4 .34mmol·L- 1时抑制 80 % ,5 .79mmol·L- 1完全抑制 ,氯磷定不能减轻之。浓度大于 3.62mmol·L- 1的敌敌畏对单收缩也有明显抑制。

AIM To observe if dichlorvos having the direct toxicity on the diaphragm. METHODS Isolated rat diaphragm was directly stimulated with a home-made double-functional electrode after the neuromuscular synaptic transmission was blocked with tubercurarine. The contraction of the rat diaphragm caused in this way had no relation to the neuromuscular synaptic transmission. The direct action of dichlorvos could be observed by its influences on such kind of contraction. RESULTS After the neuromuscular synaptic transmission was completely blocked with tubercurarine, stimulating phrenic nerve was not able to induce the contraction of diaphragm, while directly stimulating diaphram could still result in its contraction. Dichlorvos at the concentration of 0.724 mmol·L -1 began to inhibit the directly-stimulated tetanic-like contraction of the rat diaphragm. At the concentration of 4.34 mmol·L -1, such contraction was inhibited by 80%. At the concentration of 5.79 mmol·L -1, both the tetanic-like and simple contractions were completely inhibited by dichlorvos, pralidoxime could not reduce the inhibition. CONCLUSION Dichlorvos has direct inhibition effect on the diaphragm, which is unrelated to the block of the neuromuscular transmission and the inhibition of acetylcholinesterases.