Pseudo-muscarine

Choline nitrite, or pseudo-muscarine, was at one time thought to be identical with natural muscarine, the highly poisonous alkaloid of the mushroom Amanita muscaria (Fly Agaric), and to be the aldehyde corresponding to choline. Both suppositions are wrong. The natural alkaloid is much more toxic than choline nitrite, and its effects are antagonised by atropine, which has little protective effect against the synthetic ester. 

Inhibition of AChE can increase the stimulation of both muscarinic and nicotinic receptors produced by synaptically released ACh. Nicotinic receptors can also be stimulated directly by AChE inhibitors with a quaternary ammonium group, and this can potentiate their cholinomimetic effect. Finally, although inhibition of true AChE is most important for potentiating the synaptic activity of ACh, several AChE inhibitors also inhibit the pseudo-ChE in plasma. This can permit plasma concentrations of ACh to rise markedly and activate endothelial muscarinic receptors. 

Derivatives of Tropine and Pseudo-tropine. The configuration of the 3-OH group in the tropine part of the molecule has significant influence on the activity at the muscarinic receptor (Table 3.15). The derivatives of i//-tropine (pseudotropine, 3) are less active the activity ratio for the if/ compound relative to the isomeric tropine varies from 2 to 13, but more information is needed on this point. 

---