The Journal of Neurophysiology Vol. 83 No. 4 April 2000, pp. 2349-2354
Copyright ©2000 by the American Physiological Society

Calcium Currents in Retrogradely Labeled Pyramidal Cells From Rat Sensorimotor Cortex

Department of Anatomy and Neurobiology, University of Tennessee, Memphis, Tennessee 38163

Stewart, Ansalan and Robert C. Foehring. Calcium Currents in Retrogradely Labeled Pyramidal Cells From Rat Sensorimotor Cortex. J. Neurophysiol. 83: 2349-2354, 2000. Our previous studies of calcium (Ca²⁺) currents in cortical pyramidal cells revealed that the percentage contribution of each Ca²⁺ current type to the whole cell Ca²⁺ current varies from cell to cell. The extent to which these currents are modulated by neurotransmitters is also variable. This study was directed at testing the hypothesis that a major source of this variability is recording from multiple populations of pyramidal cells. We used the whole cell patch-clamp technique to record from dissociated corticocortical, corticostriatal, and corticotectal projecting pyramidal cells. There were significant differences between the three pyramidal cell types in the mean percentage of L-, P-, and N-type Ca²⁺ currents. For both N- and P-type currents, the range of percentages expressed was small for corticostriatal and corticotectal cells as compared with cells which project to the corpus callosum or to the general population. The variance was significantly different between cell types for N- and P-type currents. These results suggest that an important source of the variability in the proportions of Ca²⁺ current types present in neocortical pyramidal neurons is recording from multiple populations of pyramidal cells.