[Effect of deoxypodophyllotoxin on membrane potential of dorsal unpaired median neurons and its relationship with sodium channel].
OBJECTIVE
to investigate the effect of deoxypodophyllotoxin (DOP) on membrane potential of dorsal unpaired median neurons (DUM, neurons) and its correlation with sodium channel.


METHODS
DUM neurons were labeled with DiBAC4(3). Laser scanning confocal microscope was used to monitor the changes of membrane potential at real time on these neurons that were treated with different concentrations of the DOP. The effect of sodium channel blocker tetrodotoxin (TTX) on the changes was also observed.


RESULTS
membrane potential depolarization induced by the DOP peaked at 5 min and became stabilized after 8min. After compared with fluorescence intensity without treatment, the normalized fluorescence intensity was 69.6 ± 3.0, 72.1 ± 2.7, 77.8 ± 3.6, 86.2 ± 3.1 in cells which were treated with 1, 5, 25, 125 micromol/L DOP, respectively. These numbers were significantly lower than those from untreated control cells (P < 0.01). When DUM neurons were co-incubated with 1 micromol/L TTX for 20 min, then treated with 25 micromol/L DOP, the intensity changed to 63.6 ± 5.4, which was similar to that of the control (P > 0.05). This indicated that the effect of DOP could be completely inhibited by TTX.


CONCLUSIONS
DOP induced membrane depolarization of DUM neurons in the range of 1 approximately 125 micromol/L and the sodium channel should be involved in this process.
Key Laboratory of Contemporary Toxicology, Nanjin Medical University, Nanjing 210029, China.
Qin
Q
Sun
Peng
P
Xu
Li-Shan
LS
Wang
Fan
F
Hu
Jie
J
Cheng
Hang
H
Xiao
Rong
R
Gao
D000818:Animals; D002478:Cells, Cultured; D004365:Drugs, Chinese Herbal; D017952:Ganglia, Invertebrate / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D010526:Periplaneta / Q000187:drug effects / Q000502:physiology; D011034:Podophyllotoxin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism*
D004365:Drugs, Chinese Herbal; D015222:Sodium Channels; C014451:deoxypodophyllotoxin; D011034:Podophyllotoxin