Effect of /-ephedrine on cholinergic neurotransmission in the isolated guinea pig ileum.

Abstract

Abstract-In the isolated guinea pig ileum, the effects of /-ephedrine on the twitch response to field stimulation were investigated in the presence of propranolol. Ephedrine and clonidine inhibited the twitch response but not the contraction to exogenous acetylcholine. The inhibitory effect of clonidine was significantly diminished by yohimbine pretreatment. However, the inhibitory effect of ephedrine was not influenced by yohimbine, sulpiride or 6-hydroxydopamine (6-OHDA) pretreatment. Most of this action of ephedrine appeared to be cholinergic pre junctional in nature, but unrelated to activation of prejunctional a2-adrenoceptors and dopamine sensitive receptors on the cholinergic nerves in this preparation.

β-Phenylethylamines and the isoquinoline alkaloids

“…Cyclizations of the chiral iminium salt (4) with base afforded the carbinolamine ether (5) reduction of which with benzylic cleavage yielded (6, R = H). 13 The cyclization of the vinyl sulphoxides (7) and (8), obtained by Wittig reaction from the corresponding aldehyde, was achieved by base, when the 2isomer (7) gave the tetrahydroisoquinoline (9) and the E-isomer (8) yielded the enantiomer of (9). Desulphurizing reduction of (9) yielded 5-( -)-carnegine (6, R = Me) and desulphurization of its enantiomer gave R-( +)-carnegine.I4 Mescaline and homoveratrylamine have been converted by Pictet-Spengler cyclization with the masked aldehydes (10) and ( I I ) respectively into anhalinine (12, R1 = OMe, R2 = H)15 and calycotomine (12, R1 = H, R2 = CH20H).…”