Evidence for the involvement of Na+-K+ pump and K+ conductance in the post-tetanic hyperpolarization of the tetrodotoxin-resistant C-fibers in the isolated bullfrog sciatic nerve.
The post-tetanic hyperpolarizations (PTHPs) were recorded from the isolated bullfrog sciatic nerves using a modified vaseline gap method. Repetitive stimulation of tetrodotoxin-resistant (TTX-R) C-fibers produced frequency- and activity-dependent PTHPs. The ouabain solutions (0.1 mM), the solutions (0.1 mM ouabain + 2 mM tetraethylammonium (TEA)) and 5 mM TEA solutions reduced the PTHP amplitude to 56.2 +/- 10.7% (mean +/- SD, n = 9), to 37.0 +/- 12.3% (n = 8), to 76.0 +/- 10.9% (n = 5) of the control value, respectively. Each pair of the three solutions revealed a significant difference in their effects on the PTHP (P < 0.01). Furthermore, the Li-Ringer solutions and the solutions (Li-Ringer + 2 mM TEA) reduced the PTHP amplitude as well, thus resembling ouabain effects. These results strongly suggest that the repetitive stimulation of TTX-R C-fibers activates the membrane Na+-K+ pump resulting in a major part of the PTHP and induces TEA-sensitive K+ conductance composing a minor part of the PTHP, which might modulate repetitive firing of TTX-R C-fibers.
Kobayashi
J
J
Department of Prosthetic Dentistry I, Faculty of Dentistry, Kyushu University, Fukuoka, Japan.
Ohta
M
M
Terada
Y
Y
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004553:Electric Conductivity; D007552:Isotonic Solutions; D009412:Nerve Fibers / Q000187:drug effects / Q000201:enzymology*; D011188:Potassium / Q000378:metabolism*; D011892:Rana catesbeiana; D000077331:Ringer's Solution; D012584:Sciatic Nerve / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D007552:Isotonic Solutions; D013779:Tetrodotoxin; D019789:Tetraethylammonium; D000077331:Ringer's Solution; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium