Tilmisany A K, Abdel Aziz A, Osman O H, Mustafa A A
Toxicon. 1986;24(11-12):1162-5. doi: 10.1016/0041-0101(86)90143-1.
Venoms from N. haje, N. naja, N. nigricollis and N. mossambica were tested on the isolated guinea-pig trachea. The four venoms (1-30 micrograms/ml) contracted the tracheal smooth muscle after a delay of 40-60 sec. A second challenge with the venoms caused either no or a much reduced contraction or a relaxant effect. The contraction could be prevented by pretreatment with antihistaminics, but not by atropine, methysergide or indomethacin, indicating that it is due to histamine release by the venoms. This release requires extracellular Ca2+, as it could be prevented by pretreatment with verapamil. Under conditions which prevented histamine release or its effect, each of the four venoms resulted in a reproducible relaxant effect which was not blocked by propranolol. It is concluded that the venoms have one or more component(s) causing histamine release which masks the relaxation caused by another component(s) of the venoms.
对埃及眼镜蛇、印度眼镜蛇、黑颈眼镜蛇和莫桑比克射毒眼镜蛇的毒液进行了离体豚鼠气管试验。这四种毒液（1 - 30微克/毫升）在延迟40 - 60秒后使气管平滑肌收缩。再次用毒液刺激要么不引起收缩，要么收缩大大减弱，要么产生松弛作用。用抗组胺药预处理可防止收缩，但阿托品、甲基麦角新碱或消炎痛不能，这表明收缩是由于毒液释放组胺所致。这种释放需要细胞外钙离子，因为用维拉帕米预处理可防止。在防止组胺释放或其作用的条件下，四种毒液中的每一种都产生了可重复的松弛作用，这种作用不受普萘洛尔的阻断。结论是毒液含有一种或多种导致组胺释放的成分，这掩盖了毒液其他成分引起的松弛作用。
