A comparison of cinobufotenine (the quaternary derivative of 5-HT) and some related compounds with coryneine (the quaternary derivative of dopamine) on the frog rectus, guinea-pig ileum and rat fundus strip preparations.
1 Coryneine is 2.7 times as active as cinobufotenine on the frog rectus but on the guinea-pig ileum cinobufotenine is 1.5 times as active as coryneine. Cinobufotenine is a potent stimulant of parasympathetic ganglia and its effect are competitively antagonized by hexamethonium. 2 The effects of pH on activity relative to a standard whose ionisation is constant (Me4+N or the trimethylammonium analogue of tryptamine) are consistent with the phenate form being weaker than the phenolic form but the changes are smaller than with coryneine because cinobufotenine is a weaker acid. 3 The hydroxyl group makes a large contribution to activity. Cinobufotenine is 9 times as active as the analogue without a hydroxyl on the frog rectus and 12 times as active as it on the ileum. The 5-methoxy analogue is an antagonist on the frog rectus and a very weak partial agonist on the ileum. 4 Cinobufotenine and the quaternary derivative of tryptamine have less than one-thousandth of the activity of 5-hydroxytryptamine on the rat fundus strip.
D000009:Abdominal Muscles; D000818:Animals; D002027:Bufotenin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004298:Dopamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D006584:Hexamethonium Compounds / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007082:Ileum; D009130:Muscle, Smooth / Q000187:drug effects*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D011896:Rana temporaria; D051381:Rats; D012701:Serotonin / Q000031:analogs & derivatives* / Q000494:pharmacology; D013329:Structure-Activity Relationship
D006584:Hexamethonium Compounds; D000644:Quaternary Ammonium Compounds; D002027:Bufotenin; D012701:Serotonin; C027958:cinobufotenine; C012856:coryneine; D004298:Dopamine