title: Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels in cultured rat hippocampal neurons.
abstract: OBJECTIVE
  To investigate the effect of ginsenoside Rb1 on voltage-gated calcium currents in cultured rat hippocampal neurons and the modulatory mechanism.
  
  
  METHODS
  Cultured hippocampal neurons were prepared from Sprague Dawley rat embryos. Whole-cell configuration of the patch-clamp technique was used to record the voltage-gated calcium currents (VGCCs) from the hippocampal neurons,and the effect of Rb1 was examined.
  
  
  RESULTS
  Rb1 (2-100 μmol/L) inhibited VGCCs in a concentration-dependent manner, and the current was mostly recovered upon wash-out. The specific L-type Ca(2+) channel inhibitor nifedipine (10 μmol/L) occluded Rb1-induced inhibition on VGCCs. Neither the selective N-type Ca(2+) channel blocker ω-conotoxin-GVIA (1 μmol/L), nor the selective P/Q-type Ca(2+) channel blocker ω-agatoxin IVA (30 nmol/L) diminished Rb1-sensitive VGCCs. Rb1 induced a leftward shift of the steady-state inactivation curve of I(Ca) to a negative potential without affecting its activation kinetics or reversal potential in the I-V curve. The inhibitory effect of Rb1 was neither abolished by the adenylyl cyclase activator forskolin (10 μmol/L), nor by the PKA inhibitor H-89 (10 μmol/L).
  
  
  CONCLUSIONS
  Ginsenoside Rb1 selectively inhibits the activity of L-type voltage-gated calcium channels, without affecting the N-type or P/Q-type Ca(2+) channels in hippocampal neurons. cAMP-PKA signaling pathway is not involved in this effect.
authors.affiliation: Fujian Institute of Geriatrics, the Affiliated Union Hospital of Fujian Medical University, Fuzhou, China.
authors.forename: Zhi-ying
authors.initials: ZY
authors.lastname: Lin
authors.forename: Li-min
authors.initials: LM
authors.lastname: Chen
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiao-dong
authors.initials: XD
authors.lastname: Pan
authors.forename: Yuan-gui
authors.initials: YG
authors.lastname: Zhu
authors.forename: Qin-yong
authors.initials: QY
authors.lastname: Ye
authors.forename: Hua-pin
authors.initials: HP
authors.lastname: Huang
authors.forename: Xiao-chun
authors.initials: XC
authors.lastname: Chen
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D036145:Ginsenosides / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D005894:Panax / Q000737:chemistry; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D020746:Calcium Channels, L-Type; D036145:Ginsenosides; C442759:ginsenoside Rb1