Voltage-activated sodium current is inhibited by capsaicin in rat atrial myocytes.
The effects of capsaicin, the active principle of hot pepper genus Capsicum, were studied on voltage-activated, tetrodotoxin-sensitive Na+ currents in isolated rat atrial cells using the patch clamp technique in the whole-cell configuration. 0.4 and 4 microM of capsaicin produced a significant tonic block on voltage-activated Na+ current (I(Na)) evoked by a depolarizing step to -40 mV from a holding potential of -100 mV (49 +/- 7% n = 11, P < 0.05 and 72 +/- 13% n = 4, P < 0.05 respectively). We didn't observe any use-dependent block of capsaicin in our experimental conditions. Capsaicin slowed the time decay of inactivation of I(Na), and increased the time constant of the recovery of inactivation. Capsaicin and tetrodotoxin (TTX) depressed contractility of isolated electrically driven left rat atria, being the depression of maximal velocity of force development (dF/dt(max)) with respect to control values of 19 +/- 3% at 1 microM of capsaicin and 22 +/- 2% at 1 microM of TTX. These results show an inhibitory effect of capsaicin on I(Na) in isolated atrial cells that may modify the electrical and contractile function of the rat heart.
Milesi
V
V
Anatomía y Fisiología, Departamento de Ciencias Biológicas, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calles 47 y 115, La Plata (1900), Argentina. veronica@hanuel.biol.unlp.edu.ar
Rebolledo
A
A
Alvis
A G
AG
Raingo
J
J
Grassi de Gende
A O
AO
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D002478:Cells, Cultured; D004553:Electric Conductivity; D005071:Evoked Potentials; D006325:Heart Atria / Q000187:drug effects; D007700:Kinetics; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D013779:Tetrodotoxin; D002211:Capsaicin