ABSTRACT
This study consists of two parts, first to compare the pharmacological profile of atropine and CEB-1957 substance toward muscarinic receptor subtypes. In various rat brain structures, binding properties were determined by competition experiments of [3H]pirenzepine, [3H]AF-DX 384, and [3H]4-DAMP in quantitative autoradiography of M1, M2, and M3 muscarinic receptor subtypes, respectively. Competition curves have shown that atropine presents similar nanomolar inhibition constants toward each subtype, while CEB-1957 has distinct affinities (Ki from 0.26 to 73 nM) with the following range order: M3 > or = M2 > M1. The second part is to compare atropine and CEB-1957 (in combination with pralidoxime) for their ability to protect against the lethality induced by 2 x LD50 of the acetylcholinesterase inhibitor sarin. CEB-1957 reduced the mortality at doses 10 times lower than atropine. Finally, from these results, it is proposed that a selective blockade of M2 and M3 receptor subtypes could play a pivotal role in the protective effect against sarin poisoning.
