Article date: August 1980
By: R.B. BARLOW, K.N. BURSTON, in Volume 69, Issue 4, pages 597-600
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 effects are competitively antagonized by hexamethonium.
The effects of pH on activity relative to a standard whose ionisation is constant (Me4N+ 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.
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.
Cinobufotenine and the quaternary derivative of tryptamine have less than one‐thousandth of the activity of 5‐hydroxytryptamine on the rat fundus strip.
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 effects are competitively antagonized by hexamethonium.
The effects of pH on activity relative to a standard whose ionisation is constant (Me4N+ 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.
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.
Cinobufotenine and the quaternary derivative of tryptamine have less than one‐thousandth of the activity of 5‐hydroxytryptamine on the rat fundus strip.
DOI: 10.1111/j.1476-5381.1980.tb07909.x
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