Zhang Y H, Kenyon J L, Nicol G D
Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120, USA.
J Neurophysiol. 2001 Jan;85(1):362-73. doi: 10.1152/jn.2001.85.1.362.
The whole cell patch-clamp technique was used to examine the effects of protein kinase C (PKC) activation (via the phorbol ester, phorbol 12,13 dibutyrate, PDBu) on the modulation of potassium currents (I(K)) in cultured capsaicin-sensitive neurons isolated from dorsal root ganglia from embryonic rat pups and grown in culture. PDBu, in a concentration- and time-dependent manner, reduced I(K) measured at +60 mV by approximately 30% if the holding potential (V(h)) was -20 or -47 mV but had no effect if V(h) was -80 mV. The PDBu-induced inhibition of I(K) was blocked by pretreatment with the PKC inhibitor bisindolylmaleimide I and I(K) was unaffected by 4-alpha phorbol, indicating that the suppression of I(K) was mediated by PKC. The inhibition of I(K) by 100 nM PDBu at a V(h) of -50 mV was reversed over several minutes if V(h) was changed to -80 mV. In addition, intracellular perfusion with 5 mM bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA) or pretreatment with omega-conotoxin GVIA or Cd(2+)-Ringer, but not nifedipine, prevented the PDBu-induced suppression of I(K) at -50 mV, suggesting that a voltage-dependent influx of calcium through N-type calcium channels was necessary for the activation of PKC. The potassium channel blockers tetraethylammonium (TEA, 10 mM) and 4-aminopyridine (4-AP, 3 mM and 30 microM) reduced I(K), but only TEA attenuated the ability of PDBu to further inhibit the current, suggesting that the I(K) modified by PDBu was sensitive to TEA. Interestingly, in the presence of 3 mM or 30 microM 4-AP, 100 nM PDBu inhibited I(K) when V(h) was -80 mV. Thus 4-AP promotes the capacity of PDBu to reduce I(K) at -80 mV. We find that activation of PKC inhibits I(K) in rat sensory neurons and that voltage-dependent calcium entry is necessary for the development and maintenance of this inhibition.
采用全细胞膜片钳技术,研究蛋白激酶C(PKC)激活(通过佛波酯,佛波醇12,13 - 二丁酸酯,PDBu)对从胚胎大鼠幼崽背根神经节分离并在培养中生长的辣椒素敏感神经元中钾电流(I(K))调制的影响。如果钳制电位(V(h))为-20或-47 mV,PDBu以浓度和时间依赖的方式使在+60 mV测量的I(K)降低约30%,但如果V(h)为-80 mV则无影响。PKC抑制剂双吲哚马来酰胺I预处理可阻断PDBu诱导的I(K)抑制,且I(K)不受4-α佛波醇影响,表明I(K)的抑制是由PKC介导的。如果将V(h)变为-80 mV,100 nM PDBu在V(h)为-50 mV时对I(K)的抑制在几分钟内可逆转。此外,用5 mM双(邻氨基苯氧基)-N,N,N',N'-四乙酸(BAPTA)进行细胞内灌流或用ω-芋螺毒素GVIA或Cd(2+) - 林格液预处理,但不用硝苯地平,可防止PDBu在-