The effects of phorbol-12,13-dibuterate (PDBu) on total sodium current (I(Na)-total), tetrodotoxin-resistant sodium current (I(Na)-TTXr), 4-AP-sensitive potassium current (I(A)) and TEA-sensitive potassium current (I(K)) in trigeminal ganglion (TG) neurons were investigated. Whole-cell patch clamp techniques were used to record ion currents in cultured TG neurons of rats. Results revealed that 0.5 micromol/L PDBu reduced the amplitude of I(Na)-total by (38.3+/-4.5)% (n=6, P<0.05), but neither the G-V curve (control: V (0.5)=-17.1+/-4.3 mV, k=7.4+/-1.3; PDBu: V (0.5)=-15.9+/-5.9 mV, k=5.9+/-1.4; n=6, P>0.05) nor the inactivation rate constant (control: 3.6+/-0.9 ms; PDBu: 3.6+/-0.8 ms; n=6, P>0.05) was altered. 0.5 micromol/L PDBu could significantly increase the amplitude of I(Na)-TTXr by (37.2+/-3.2)% (n=9, P<0.05) without affecting the G-V curve (control: V (0.5)=-14.7+/-6.0 mV, k=6.9+/- 1.4; PDBu: V (0.5)=-11.1+/-5.3 mV, k=8.1+/-1.5; n=5, P>0.05) or the inactivation rate constant (control: 4.6+/-0.6 ms; PDBu: 4.2+/-0.5 ms; n=5, P>0.05). 0.5 mumol/L PDBu inhibited I(K) by (15.6+/-5.0) % (n=16, P<0.05), and V (0.5) was significantly altered from - 4.7+/-1.4 mV to -7.9 +/-1.8 mV (n=16, P<0.05). I(A) was not significantly affected by PDBu, 0.5 mumol/L PDBu decreased I(A) by only (0.3+/-3.2)% (n=5, P>0.05). It was concluded that PDBu inhibited I(Na)-total but enhanced I(Na)-TTXr, and inhibited I(K) without affecting I(A). These data suggested that the activation of PKC pathway could exert the actions.

AIMTo investigate the role of serine/threonine protein phosphatases in regulation of cell signal transduction on voltage-dependent sodium channels in rat trigeminal ganglion (TRG) neurons. METHODSWhole-cell patch clamp techniques were used to record the total sodium current (INa-T) and the tetrodotoxin-resistant sodium current (INa-TTX-R) before and after okadaic acid, a potent inhibitor of the serine/threonine protein phosphatases 1 and 2A, perfusion on adult rat TRG neurons. RESULTS1μmol*L-1 okadaic acid inhibited INa-T by (20±13)% (n=9, P<0.05) and INa-TTX-R by (4±3)% (n=6, P<0.05), respectively. The inhibition on INa-T was significantly greater than that on INa-TTX-R (P<0.05). Furthermore, 1μmol*L-1 okadaic acid produced significant 3-4 mV hyperpolarizing shifts in the conductance-voltage curves of INa-T, while it had no effect on that of INa-TTX-R. CONCLUSIONThe serine/threonine protein phosphatases take part in the regulation of total and TTX-R sodium channels on rat TRG neurons. In addition, small-diameter TRG neurons express various voltage-gated sodium channel with different sensitivity to okadaic acid.

AIM To investigate the effects of serine/threonine protein phosphatases in regulation of cell signal transduction on voltage-gated potassium and calcium channels in cultured rat trigeminal ganglion (TRG) neurons. METHODS Whole-cell patch clamp technique was used to record the potassium and calcium currents from adult rat TRG neurons before and after perfusion of okadaic acid, a potent inhibitor of the serine/threonine protein phosphatases 1 and 2A. RESULTS Okadaic acid 1 μmol·L-1 inhibited transient outwards potassium currents (IA) by 28.6%, increased delay rectified potassium currents (IK) and calcium currents (ICa) by 22.7% and 20.0%, respectively. okadaic acid 1 μmol·L-1 produced significant hyperpolarizing shifts in the conductance-voltage (G-V) curves and inactivation curves of IA , also produced significant hyperpolarizing shifts in the G-V curves of IK, while it had no effect on the activation and inactivation kinetics of ICa. CONCLUSION Serine/threonine protein phosphatases 1 and 2A may be involved in the modulation of voltage-gated potassium and calcium channels on rat TRG neurons. In addition, voltage-gated potassium and calcium channels show different dependence on the dephosphorylation reactions of PP1 and PP2A phosphatases.

The different effects of capsaicin on I(A) and I(K) currents in pain-conduct neurons of trigeminal ganglia (TG) were investigated. In cultured TG neurons of rats, whole-cell patch clamp techniques were used to record the I(A) and I(K) before and after capsaicin perfused. Results revealed that 1 micromol/L capsaicin could inhibit the amplitude of I(A) by 48.2% (n = 10, P < 0.05), but had no inhibitory effect on I(K) (n = 7, P > 0.05). Ten micromol/L capsaicin could significantly inhibit the amplitude of I(A) by 93.2% (n = 8, P < 0.01), but only slightly inhibit the amplitude of I(K) by 13.2% (n = 7, P < 0.05). Neither 1 micromol/L nor 10 micromol/L capsaicin had effects on the active curve of I(A) and I(K). It was concluded that capsaicin could selectively inhibit the I(A) current, and this effect might involve in the analgesic mechanisms of capsaicin.

To investigate the effect of interleukin-1beta (IL-1beta) on I(A) and I(K) currents in cultured murine trigeminal ganglion (TG) neurons, whole-cell patch clamp technique was used to record the I(A) and I(K) currents before and after 20 ng/mL I(L)-1beta perfusion. Our results showed that 20 ng/mL IL-1beta inhibited I(A) currents (18.3 +/- 10.7)% (n=6, P<0.05). I(L)-1beta at 20 ng/mL had no effect on G-V curve of I(A) but moved the H-infinity curve V0.5 from -36.6+/-6.1 mV to -42.4+/-5.2 mV (n=5, P<0.01). However, 20 ng/mL IL-1beta had effect on neither the amplitude nor the G-V curve of I(K). IL-1beta was found to selectively inhibit I(A) current in TG neurons and the effect may contribute to hyperalgesia under various inflammatory conditions.

This experiment aimed to investigate the effect of adrenergic system in the subnucleus commissuriu of nucleus solitrius tractus (CNTS) on renal nerve discharges. Norepinephrine (NE) was microinjected into the CNTS of rabbits and mean arterial blood pressure (MAP) and renal nerve discharges (FRND) were synchronously recorded. The results indicated that (1) microinjection of norepinephine into the CNTS of rabbit could significantly attenuate the frequency of renal nerve discharge, and at the same time decrease markedly the mean arterial pressure. (2) Microinjection of 0.3 nmol yohimbin into CNTS had no significant influence on FRND and MAP, but could attenuate and even reverse the effects of NE on FRND and MAP. These results suggest that microinjection of NE into CNTS may activate the alpha-adrenorecptor located in CNTS and secondarily produce a depressor effect by attenuating the activity of periphenal sympathetic nervous system.
Blood Pressure/drug effects ; Depression, Chemical ; Kidney/*innervation ; Microinjections ; Norepinephrine/*pharmacology ; Solitary Nucleus/*physiology ; Sympathetic Nervous System/drug effects ; Sympathetic Nervous System/*physiopathology ; Vasomotor System/physiopathology

Summary: This experiment aimed to investigate the effect of adrenergic system in the subnucleus commissuriu of nucleus solitrius tractus (CNTS) on renal nerve discharges. Norepinephrine (NE) was microinjected into the CNTS of rabbits and mean arterial blood pressure (MAP) and renal nerve discharges (FRND) were synchronously recorded. The results indicated that (1) microinjection of norepinephine into the CNTS of rabbit could significantly attenuate the frequency of renal nerve discharge, and at the same time decrease markedly the mean arterial pressure. (2) Microinjection of 0.3 nmol yohimbin into CNTS had no significant influence on FRND and MAP, but could attenuate and even reverse the effects of NE on FRND and MAP. These results suggest that microinjection of NE into CNTS may activate the alpha-adrenorecptor located in CNTS and secondarily produce a depressor effect by attenuating the activity of peripheral sympathetic nervous system.

The different effects of capsaicin on IA and IK currents in pain-conduct neurons of trigeminal ganglia (TG) were investigated. In cultured TG neurons of rats, whole-cell patch clamp techniques were used to record the IA and IK before and after capsaicin perfused. Results revealed that 1 μmol/L capsaicin could inhibit the amplitude of IA by 48.2% (n=10, P＜0.05), but had no inhibitory effect on IK (n=7, P＞0.05). Ten μmol/L capsaicin could significantly inhibit the amplitude of IA by 93.2% (n=8, P＜0.01), but only slightly inhibit the amplitude of IK by 13.2% (n=7,P＜0.05). Neither 1 μmol/L nor 10 μmol/L capsaicin had effects on the active curve of IA and IK.It was concluded that capsaicin could selectively inhibit the IA current, and this effect might involve in the analgesic mechanisms of capsaicin.

The effects of phorbol-12,13-dibuterate (PDBu) on total sodium current (INa-total), tetrodotoxin-resistant sodium current (INa-TTXr), 4-AP-sensitive potassium current (IA) and TEA-sensitive potassium current (IK) in trigeminal ganglion (TG) neurons were investigated.Whole-cell patch clamp techniques were used to record ion currents in cultured TG neurons of rats. Results revealed that 0.5 μmol/L PDBu reduced the amplitude of INa-total by (38.3±4.5)% (n=6, P＜0.05), but neither the G-V curve (control: V0.5 =-17.1±4.3 mV, k=7.4±1.3; PDBu: V0.5=-15.9±5.9 mV, k=5.9±1.4; n=6, P＞0.05) nor the inactivation rate constant (control: 3.6±0.9 ms; PDBu: 3.6±0.8 ms; n=6, P＞0.05) was altered. 0.5 μmol/L PDBu could significantly increase the amplitude of INa-TTXr by (37.2± 3.2)% (n=9, P＜0.05) without affecting the G-V curve (control: V0.5=-14.7±6.0 mV, k=6.9±1.4; PDBu: V0.5=-11.1±±5.3 mV, k=8.1±1.5; n=5, P＞0.05) or the inactivation rate constant (control: 4.6±±0.6 ms; PDBu: 4.2±0.5 ms; n=5, P＞0.05). 0.5 μmol/L PDBu inhibited IK by (15.6±5.0) % (n=16, P＜0.05), and V0.5 was significantly altered from - 4.7±1.4 mV to -7.9 ±1.8 mV (n=16, P＜0.05). IA was not significantly affected by PDBu, 0.5 μmol/L PDBu decreased IA by only (0.3±3.2)% (n=5, P＞0.05). It was concluded that PDBu inhibited INa-total but enhanced INa-TTXr, and inhibited IK without affecting IA. These data suggested that the activation of PKC pathway could exert the actions.

To investigate the effects of WIN 55,212-2 on IK in cultured rat trigeminal ganglion (TG) neurons, whole-cell patch clamp techniques were used to record the IK before and after WIN 55,212-2 perfusion at different concentrations. 30 μmol/L WIN 55,212-2 markedly (35.7 %±7.3%, P＜0. 01, n=8) inhibited IK currents, and the currents were partially recovered after washing.30μmol/L WIN 55,212-2 also induced a significant depolarizing shift in conductance-voltage parameters (control: V0.5 =10.43 ± 4.25 mV, k= 16.27±3.86; WIN 55,212-2: V0. 5 =24.71±3.91mV, k =16.69±2.75; n = 8, P＜0.01 for V0. 5). 0.01μmol/L WIN 55,212-2 slightly (27.0 %± 7.9 %, P＜0.05, n=7) increased IK currents, but had no significant change in conductance voltage parameters (control: V0.5 =10. 74±5. 27 mV, k=17. 33±2. 96; WIN 55,212-2: V0.5 =11.06±2.05 mV, k=19. 69±6. 60; n=7, P＞0.05 for V0.5 and k). These results suggested that WIN 55,212-2 has dual action, which might be through different receptors.