Potentiation of rabbit trigeminal responses to capsaicin in a low pH environment.
The sensitivity of 35 adult rabbit trigeminal ganglion neurons to low pH (pH 6.0), 10 microM capsaicin (CAP) and 10 microM capsaicin at low pH (CAP@pH6.0) was studied using voltage-clamp whole-cell recording techniques. Neurons responded to pH 6.0 with a transient inward current, followed by a more slowly activating (sustained) net inward current. Responses to capsaicin showed only a sustained current. Capsaicin caused an increase in membrane conductance, whereas responses to low pH were associated with either a net increase or decrease in conductance. A subset of neurons (n = 14) responded to CAP@pH6.0 with a sustained current which exceeded the sum of the peak sustained currents evoked by CAP and pH 6.0 applied singularly by approximately a factor of 4. The current was associated with a substantial increase in membrane conductance. The present results indicate that, in addition to a direct conductance activating effect, protons have the ability to enhance the current evoked by capsaicin.
Martenson
M E
ME
Division of Neurosurgery (L472), Oregon Health Sciences University, Portland 97201.
Ingram
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SL
Baumann
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TK
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D008297:Male; D009474:Neurons / Q000502:physiology*; D011817:Rabbits; D012668:Trigeminal Ganglion / Q000502:physiology*
D002211:Capsaicin