双甲脒对大鼠脑 α_2-肾上腺素受体的影响

Effects of Amitraz on α 2 adrenoceptors in the Rat Brain

为探讨双甲脒与α２－肾上腺素受体的相互关系以及为甲脒类农药中毒的受体学说提供进一步的证据，采用放射性配体结合技术研究双甲脒与α２－肾上腺素受体的相互关系。体外受体结合试验表明，双甲脒抑制大鼠前脑３Ｈ－可乐定结合的ＩＣ５０值为４５．８ｎｍｏｌ／Ｌ，且明显增大３Ｈ－可乐定结合的解离常数（Ｋｄ值），但对３Ｈ－可乐定的最大结合容量（Ｂｍａｘ值）无影响。对各脑区α２－受体作用的研究表明，一次大剂量双甲脒（７０ｍｇ／ｋｇ）明显抑制大鼠大脑皮层和脑干的３Ｈ－可乐定结合，但海马、纹状体和小脑的３Ｈ－可乐定结合量无改变。多次小剂量双甲脒染毒（７ｍｇ／ｋｇ，连续１０日）对大脑皮层３Ｈ－可乐定结合的抑制程度小于一次大剂量双甲脒的抑制效应。上述结果进一步支持脑α２－肾上腺素受体是双甲脒毒作用部位的假说。

In order to study the relationship between amitraz and α 2 adrenoceptors and make a further evidence for the receptor theory of formamidine pesticide poinsoning,this paper presented a study on the interaction of the pesticide amitraz with brain α 2 adrenoceptors using radioactive lig and binding techniques.Amitraz was a potent inhibitor of the binding of 3H clonidine to rat forebrain with an IC 50 of 45.8nM in vitro.The saturation binding study showed that amitraz did not alter the maximal capacity(Bmax)of 3H clonidine,but significantly decreased its affinity with an increase in the Kd value.A single dose of amitraz (70 mg/kg i.p.)significantly decreased 3H clonidine binding in cerebral cortex and brain stem. but not in hippocampus,striatum and cerebellum.Repeated dose of amitraz (7mg/kg per day for 10 days )also decreased 3H clonidine binding in cerebral cortex,but the inhibition was less potent than that of above dose of amitraz (70 mg/kg).The results of the present study further supported the hypothesis that amitraz acts on α 2 adrenocepters to cause toxic actions in mammals.