Ruthenium red as a selective capsaicin antagonist of the motor response to capsaicin in the human isolated ileum.
We have investigated the effect of ruthenium red, omega-conotoxin fraction GVIA (CTX) and tetrodotoxin (TTX) on the relaxation produced in the circular muscle of the human isolated ileum by capsaicin, electrical field stimulation (EFS) or vasoactive intestinal polypeptide (VIP). Ruthenium red (10 microM) selectively blocked the capsaicin-evoked relaxation while leaving the response to EFS or VIP unaffected. CTX had no significant effect on the various stimuli. TTX blocked the relaxation due to EFS but not that due to capsaicin or VIP. It is concluded that capsaicin excitation of primary afferents in the human ileum, leading to VIP release and muscle relaxation, occurs with mechanisms similar to those operating in animal tissues and that ruthenium red acts as a selective capsaicin antagonist in the human ileum.
Giuliani
S
S
Pharmacology Department, A. Menarini Pharmaceuticals, Florence, Italy.
Turini
D
D
Barbanti
G
G
Maggi
C A
CA
D000368:Aged; D002211:Capsaicin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D004558:Electric Stimulation; D006801:Humans; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D008875:Middle Aged; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D012430:Ruthenium Red / Q000494:pharmacology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D012430:Ruthenium Red; D014660:Vasoactive Intestinal Peptide; D002211:Capsaicin