The Journal of Neurophysiology Vol. 84 No. 5 November 2000, pp. 2477-2483
Copyright ©2000 by the American Physiological Society
Effect of Extracellular HCO3
on Na+
Channel Characteristics in Hippocampal CA1 Neurons
Xiang Q.
Gu,1
Hang
Yao,1 and
Gabriel G.
Haddad1,2
1Department of Pediatrics (Section of
Respiratory Medicine) and 2Department of
Cellular and Molecular Physiology, Yale University School of
Medicine, New Haven, Connecticut 06510
Gu, Xiang Q.,
Hang Yao, and
Gabriel G. Haddad.
Effect of Extracellular HCO3 on Na+
Channel Characteristics in Hippocampal CA1 Neurons. J. Neurophysiol. 84: 2477-2483, 2000. The effect of
HCO3
/CO2 on
membrane properties of isolated hippocampal CA1 neurons was studied
with the use of the whole cell configuration of the patch-clamp
technique. Neurons were acutely dissociated from 21- to 30-day-old
mice. In the current-clamp mode,
HCO3/CO2
significantly hyperpolarized CA1 neurons by more than 10 mV and
decreased their input resistance. In addition, the overall excitability
of these neurons was lower in the presence of
HCO3/CO2 than in
HEPES. Spontaneous and evoked action potential firing frequency was
lower in the presence of
HCO3/CO2 than in
its absence. In the voltage-clamp mode, both activation and
steady-state inactivation of a fast Na+ current
were shifted in the hyperpolarized direction in such a way that the
window currents were smaller in
HCO3/CO2 than in
HEPES. Recovery from inactivation and deactivation from the open state
of the fast Na+ current was slower in
HCO3/CO2 than in
HEPES. We conclude that
HCO3/CO2
decreases the intrinsic excitability of CA1 neurons by altering not
only the passive properties of the neuronal membranes but also by
changing several characteristics of the fast Na+
current, including activation and inactivation kinetics as well as the
recovery from inactivation and deactivation.
