Effect of capsaicin on membrane currents in cultured vascular smooth muscle cells of rat aorta.
The application of capsaicin (1 microM) produced a minor relaxant effect in endothelium-denuded rat aortae. However, capsaicin caused a greater relaxation of blood vessels precontracted with high K+ or phenylephrine. The effects of capsaicin on the ionic currents were also examined in A7r5 vascular smooth muscle cells. The tight-seal whole-cell voltage clamp technique was used. Capsaicin inhibited the Ba2+ inward current (IBa) through the voltage-dependent L-type Ca2+ channel in a concentration-dependent fashion, whereas calcitonin gene-related peptide and phenylephrine produced a minor increase in IBa. Capsaicin did not alter the overall shape of current-voltage relationship of IBa. However, capsaicin (3 microM) shifted the quasi-steady-state inactivation curve of IBa to more negative membrane potential by about 5 mV. These effects of capsaicin on IBa were reversible. In addition, capsaicin had inhibitory effects on voltage dependent K+ currents. These results suggest that inhibition of the voltage-dependent L-type Ca2+ channel is involved in the capsaicin-induced relaxation of the vascular smooth muscle, whereas capsaicin-induced inhibition of voltage-dependent K+ channels might produce an increase in cell excitability.
Lo
Y C
YC
Department of Pharmacology, Kaohsiung Medical College, Taiwan.
Wu
S N
SN
Wu
J R
JR
Chen
I J
IJ
D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar
D007473:Ion Channels; D002211:Capsaicin