Phorbol Ester-Induced Inhibition of Potassium Currents in Rat Sensory Neurons Requires Voltage-Dependent Entry of Calcium

• Published in: Journal of neurophysiology Vol. 85; no. 1; pp. 362 - 373
• Main Authors: Zhang, Yi-Hong, Kenyon, J. L, Nicol, G. D
• Format: Journal Article
• Language: English
• Published: United States Am Phys Soc 01-01-2001
• Subjects: 4-Aminopyridine - pharmacology; Analysis of Variance; Animals; Calcium - metabolism; Calcium - pharmacology; Calcium Channel Blockers - pharmacology; Cells, Cultured; Chelating Agents - pharmacology; Dose-Response Relationship, Drug; Enzyme Inhibitors - pharmacology; Ganglia, Spinal - cytology; Ganglia, Spinal - drug effects; Ganglia, Spinal - metabolism; Membrane Potentials - drug effects; Neurons, Afferent - cytology; Neurons, Afferent - drug effects; Neurons, Afferent - metabolism; Patch-Clamp Techniques; Phorbol 12,13-Dibutyrate - pharmacology; Potassium Channel Blockers; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Rats; Tetraethylammonium - pharmacology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.2001.85.1.362

  1 Department of Pharmacology and Toxicology,
Indiana University School of Medicine, Indianapolis, Indiana
46202-5120; and   2 Department of Physiology and
Cell Biology/MS352, University of Nevada School of Medicine, Reno,
Nevada 89557
Zhang, Yi-Hong,
J. L. Kenyon, and
G. D. Nicol.
Phorbol Ester-Induced Inhibition of Potassium Currents in Rat
Sensory Neurons Requires Voltage-Dependent Entry of Calcium. J. Neurophysiol. 85: 362-373, 2001. 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
~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- 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 -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 µM) 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 µM 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.