Novel persistent activation of muscarinic M1 receptors by xanomeline.

The muscarinic agonists, xanomeline and carbachol, displayed similar intrinsic activities in stimulating neuronal nitric oxide synthase at muscarinic M1 receptors in Chinese hamster ovary (CHO) cells, with xanomeline being more potent. Pre-incubation (1 h) with 1 microM xanomeline, followed by extensive washing, resulted in a significantly elevated basal response, which was absent on co-incubation with atropine. This phenomenon was not observed with carbachol. This is the first report of a persistent, receptor-activating effect of a muscarinic agonist.