MPP+（1-甲基-4-苯基吡啶）是一个分子式为C₁₂H₁₂N带正电的化合物。它能够影响线粒体中的氧化磷酸化，造成ATP耗尽及细胞死亡，因此具有毒性。 同时，它还能阻断儿茶酚胺的合成，减少多巴胺和心脏中去甲肾上腺素的水平，和引发酪氨酸羟化酶的失活。

神经毒素MPTP在大脑里会被单胺氧化酶B转化成MPP+，后者能够杀死黑质中某些产生多巴胺的神经细胞，从而导致灵长类动物产生类似帕金森氏症的症状。

MPP+的氯化物曾被用作名为牧草快（cyperquat）的除草剂，而该除草剂的化学结构与百草枯十分相似。

MPP+ (1-methyl-4-phenylpyridinium) is a positively charged molecule with chemical formula C₁₂H₁₂N. It is toxic and acts by interfering with oxidative phosphorylation in mitochondria by inhibiting complex I, leading to the depletion of ATP and cell death. Mitochondria in cells treated with MPP+ also display a phenotype indicative of apoptosis: small, round, and fewer in number. It also inhibits the synthesis of catecholamines, reduces levels of dopamine and cardiac norepinephrine, and inactivates tyrosine hydroxylase.