ELECTROPHYSIOLOGICAL PROPERTIES OF CANINE CARDIAC GANGLION-CELL TYPES

Intracellular recordings were made from 110 canine cardiac ganglion ce lls to study their electrophysiological properties. According to their discharge responses to depolarizing currents, these neurons were clas sified as tonic, phasic and non-discharging cells. Of these cell types , the order of the resting membrane potentials was non-discharging > p hasic > tonic cells, which was the reverse of the order of their input resistances. Tonic and phasic cells could not be distinguished by the nature of their after hyperpolarizations which involved Ca2+-sensitiv e K+ currents. Although both cell types demonstrated fast Na+ and slow Ca2+-mediated action potentials, the tonic cells' action potentials w ere more sensitive to tetrodotoxin than those of the phasic cells.