| TRPV4 is found as osmosensor. The non-PKC-activating synthetic phorbol ester 4a-phorbol 12,13-didecanoate (4аPDD) is a very robust and potent activator of TRPV4. The mechanisms of cell swelling and 4aPDD acting TRPV4 have not been known clearly. TRPV4 is an outwardly rectifying cation channel, calcium and sodium ion can be permeated. In the study, the effects of hypotonic solution and the phorbol ester 4аPDD on the sodium channels in the cultured trigeminal ganglion neurons were investigated through electrophysiological methods.(1)Whole-cell patch clamp technique was used to investigate the effect of hypotonic solution on the voltage-dependent sodium currents. The results indicated that: hypotonic solution could inhibit the voltage-dependent sodium currents in osmotic pressure dependent manner. The inhibition rate of voltage-dependent sodium currents by 280mOsm,260mOsm,220mOsm were 24.2%±10.2% (n=10, P < 0.05), 45.7%±15.6% (n=8, P < 0.05), 70.5%±18.1%(n=6, P < 0.05),respectively, and the IC50 was 268mOsm。The threshold potential of voltage-dependent sodium currents were 28.0mV,22.7 mV,17.4mV,7.3 mV (n=6, P < 0.05) by 300mOsm,280mOsm,260mOsm,220mOsm respectively. Hypotonic solution had no effect on the steady-state activation; hyperpolarizing shifts in the steady-state inactivation curve of voltage-dependent sodium currents. The V1/2 and k of inactivation were V1/2=-45.8±9.6 mV , k=-17.54±6.9 ; V1/2=-47.2±7.8 mV, k=-17.1±6.0 ;V1/2=-56.4±11.2mV, k=-14.4±5.8;V1/2=-60.6±10.8mV, k=-11.3±4.2 (n=6, P < 0.05) respectively。(2)Whole-cell patch clamp technique was used to investigate the effect of 4аPDD on the voltage-dependent sodium currents. Phorbol ester could also inhibit the voltage-dependent sodium currents in concentration dependent manner. The inhibition rate of voltage-dependent sodium currents by 0.1,0.3,1,3,10μmol·L-1 4аPDD were 24.68±7.2%(n=8, P < 0.05),32.02±9.4%(n=7, P < 0.05),52.7±12.2%(n=6, P < 0.05),67.48±9.8%(n=7, P < 0.05),73.9±14.6%(n=6, P < 0.05),respectively, and the IC50 was 0.41μmol·L-1。0.1μmol·L-1 4аPDD had no effect on steady-state activation and inactivation curve of voltage-dependent sodium currents(n=6, P > 0.05). Key words: TRPV4 (transient receptor potential channel vanilloid subfamily 4), Patch clamp, Sodium current, Hypotonic solution, Phorbol ester, 4аPDD (4a-phorbol 12, 13-didecanoate)... |
PDF Full Text Request