Persistent Currents and Discharge Patterns in Rat Hindlimb Motoneurons

• DOI: 10.1152/jn.00380.2010
• Publication Date: 2010-07-12T10:20:23Z
• Authors: Thomas M. Hamm; Vladimir V. Turkin; Neha K. Bandekar; Derek O'Neill; Ranu Jung
• Keywords: Male; Motor Neurons; 0301 basic medicine; 03 medical and health sciences; Time Factors; Action Potentials; Animals; Female; Rats, Long-Evans; Hindlimb; Membrane Potentials; Rats

We report here the first direct measurements of persistent inward currents (PICs) in rat hindlimb motoneurons, obtained from ketamine-xylazine anesthetized rats during slow voltage ramps performed by single-electrode somatic clamp. Most motoneurons expressed PICs and current-voltage (I-V) relations often contained a negative-slope region (NSR; 13/19 cells). activated at -52.7 ± 3.89 mV, 9 mV negative to spike threshold. NSR onset was -44.2 4.1 mV. PIC amplitudes were assessed maximum measured relative extrapolated leak current NSR-onset current. conductance potentials just positive activation change slope (g(in)/g(leak)). varied widely; some exceeded 5 10 nA or current, respectively. did not vary significantly with input conductance, but normalized recruitment decreased increasing conductance. Similarly, g(in)/g(leak) Currents near resting potential on descending limbs I-V outward, ascending-limb currents. This residual outward correlated increases limb Excluding responses accommodation, matched differences between derecruitment currents, suggesting role for frequency adaptation. Comparison interspike trajectories discharge demonstrated correspondence frequency-current (f-I) range boundaries. Contributions motoneuron characteristics are discussed.