RT Journal Article
SR Electronic
T1 Resurgent Sodium Current and Action Potential Formation in Dissociated Cerebellar Purkinje Neurons
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 4517
OP 4526
DO 10.1523/JNEUROSCI.17-12-04517.1997
VO 17
IS 12
A1 Raman, Indira M.
A1 Bean, Bruce P.
YR 1997
UL http://www.jneurosci.org/content/17/12/4517.abstract
AB Voltage-dependent sodium channels were studied in dissociated cerebellar Purkinje neurons from rats. In whole-cell recordings, a tetrodotoxin (TTX)-sensitive inward current was elicited when the membrane was repolarized to voltages between −60 and −20 mV after depolarizations to +30 mV long enough to produce maximal inactivation. At −40 mV, this “resurgent” current peaked in 8 msec and decayed with a time constant of 30 msec. With 50 mm sodium as a charge carrier, the resurgent current was on average ∼120 pA. CA3 pyramidal neurons had no such current. The current may reflect recovery of inactivated channels through open states, because in Purkinje neurons (but not CA3 neurons) there was partial recovery from inactivation at −40 mV, coinciding with the rise of resurgent current. In single-channel recordings, individual channels gave openings corresponding to resurgent and conventional transient current. Action potentials were recorded from dissociated neurons under current clamp to investigate the role of the resurgent current in action potential formation. Purkinje neurons fired spontaneously at ∼30 Hz. Hyperpolarization to −85 mV prevented spontaneous firing, and brief depolarization then induced all-or-none firing of conglomerate action potentials comprising three to four spikes. When conglomerate action potentials were used as command voltages in voltage-clamp experiments, TTX-sensitive sodium current was elicited between spikes. The falling phase of an action potential is similar to voltage patterns that activate resurgent sodium current, and thus, resurgent sodium current likely contributes to the formation of conglomerate action potentials in Purkinje neurons.