title: Effects of low-dose capsaicin on L-type calcium current in guinea pig ventricular myocytes.
abstract: The purpose of this study was to examine the effects of low-dose capsaicin (CAP) on L-type calcium current (I(Ca-L) ) in guinea pig ventricular myocytes and the underlying mechanism. I(Ca-L) was examined in isolated single guinea pig ventricular myocytes by using whole-cell patch clamp technique. CAP (1-25 nmol/L) increased the voltage-dependently activated peak amplitude of I(Ca-L) and downshifted the current-voltage (I-V) curve. CAP (1, 10, 25 nmol/L) increased the peak amplitude of I(Ca-L) from -9.67+/-0.7 pA/pF to -10.21+/-0.8 pA/pF (P>0.05), to -11.37+/-0.8 pA/pF and to -12.84+/-0.9 pA/pF (P<0.05), respectively. CAP 25 nmol/L shifted the steady-state activation curve of I(Ca-L) to the left and changed half activation potential (V(0.5)) from (-20.76+/-2.0) mV to (-26.71+/-3.0) mV (P<0.05), indicating that low-dose CAP may modify the voltage-dependent activation of calcium channel. Low-dose of CAP did not affect the steady-state inactivation curve of I(Ca-L) or half-recovery time of Ca(2+) channel from inactivation. Ruthenium red (RR, 10 micromol/L), a vanilloid receptor (VR1) blocker, antagonized the effects of low-dose CAP. These results suggest that low-dose CAP increases I(Ca-L) mainly by shifting its steady-state activation curve to the left. Such effects may be mediated by VR1.
authors.affiliation: Department of Physiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang 050017, China.
authors.forename: Yan-Ping
authors.initials: YP
authors.lastname: Cheng
authors.forename: Jing-Xiang
authors.initials: JX
authors.lastname: Yin
authors.forename: Li-Ping
authors.initials: LP
authors.lastname: Cheng
authors.forename: Rui-Rong
authors.initials: RR
authors.lastname: He
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006352:Heart Ventricles; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D012430:Ruthenium Red / Q000494:pharmacology
chemical_list: D020746:Calcium Channels, L-Type; D011955:Receptors, Drug; D012430:Ruthenium Red; D002211:Capsaicin