A comparison of stereospecificity at central and peripheral 'muscarine-sensitive' acetylcholine receptors: observations with the enantiomeric forms of procyclidine and tricyclamol.

1 Procyclidine resembles hyoscine in enhancing the effects of amphetamine on ipsiversive turning by mice with a unilateral central dopamine lesion. 2 The stereospecific index for procyclidine is not greater than 10, in contrast to 173 for acetylcholine receptors in ileum from the same mice. 3 This suggests that although the central effects of procyclidine in this test involve acetylcholine receptors similar to those at peripheral sites, they cannot be identical with them unless there are differences at some secondary site, for example, if the weaker enantiomer were a stronger inhibitor of dopamine uptake or if there were a stereoselective uptake process for procyclidine itself.