Modulation of calcium currents in mouse ventral horn neurons by extracellular pH.
Neuronal activity has been shown to modulate the pH of the extracellular environment. Since neuronal circuits in the ventral horn of the spinal cord are highly active during patterned movements, and voltage-gated calcium channels play an important role in the production of spinal motoneuron output, the effects of changes in extracellular pH (pH(e)) on calcium currents in ventral horn neurons of the mouse spinal cord were examined. It is demonstrated that these channels are sensitive to modulation by pH(e). The amplitude of the current mediated by these channels increased as the pH(e) was elevated. The elevated pH(e) also led to a hyperpolarizing shift in the voltage dependence of both activation and inactivation. The opposite effects were seen for a decrease in pH(e). It was also noted that a decrease in pH(e) was associated with a faster inactivation of the current. It is concluded that voltage-gated calcium currents in ventral horn neurons are modulated by changes in pH(e), and that this modulation may play a physiologically important role in determining motoneuronal excitability during behaviors such as locomotion.
Carlin
Kevin P
KP
Spinal Cord Research Centre, Department of Physiology, The University of Manitoba, 730 William Avenue, BMSB 425, Winnipeg, Manitoba R3E 3J7, Canada. kevin@scrc.umanitoba.ca
D000818:Animals; D000831:Animals, Newborn; D000870:Anterior Horn Cells / Q000187:drug effects / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000187:drug effects / Q000502:physiology*; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology
D002121:Calcium Channel Blockers; D024642:Potassium Channels, Voltage-Gated