Jayasundar S, Vohra M M
Arch Int Pharmacodyn Ther. 1978 Apr;232(2):192-201.
Nicotine and DMPP caused contraction of rat isolated vas deferens. The contractile response was antagonized by hexamethonium, phenoxybenzamine, phentolamine, guanethidine and bretylium, but not by atropine. The response was absent in tissues depleted of their norepinephrine content. Nicotine enhanced the outflow of tritium from tissues preloaded with 3H-norepinephrine. Only 50% of the nicotine-induced tritium outflow was due to unchanged norpinephrine, the rest were due to five metabolites of norepinephrine, chiefly glycol derivatives. As tissues, at the time of exposure to nicotine contained almost all of the tritium in the form of unchanged norepinephrine, it is likely that norepinephrine, only after being released from storage sites by nicotine was acted upon by the catabolizing enzymes to form various metabolites. Desensitization and cross desensitization phenomena were observed to both nicotine and DMPP. The tissues desensitized to nicotine were, however, responsive to norepinephrine, tyramine and transmural stimulation.
尼古丁和二甲基哌啶磷（DMPP）可引起大鼠离体输精管收缩。六甲铵、酚苄明、酚妥拉明、胍乙啶和溴苄铵可拮抗这种收缩反应，但阿托品无此作用。去甲肾上腺素含量耗尽的组织无此反应。尼古丁可增加预先用3H-去甲肾上腺素标记的组织中氚的流出量。尼古丁诱导的氚流出量中只有50%是由于未变化的去甲肾上腺素，其余是由于去甲肾上腺素的五种代谢产物，主要是二醇衍生物。由于在接触尼古丁时，组织中的几乎所有氚都以未变化的去甲肾上腺素形式存在，因此很可能去甲肾上腺素只有在被尼古丁从储存部位释放后，才会被分解酶作用形成各种代谢产物。观察到对尼古丁和DMPP均有脱敏和交叉脱敏现象。然而，对尼古丁脱敏的组织对去甲肾上腺素、酪胺和跨壁刺激有反应。
