Calcium-dependent inward currents in voltage-clamped guinea-pig olfactory cortex neurones

Abstract

Guinea-pig olfactory cortex neurones in vitro (23°C–25°C) were voltage clamped by means of a single microelectrode sample-and-hold technique. In most Cs⁺-loaded neurones (in the presence of tetrodotoxin), membrane depolarization beyond −60 mV elicited inward currents, which had rapid activation kinetics. The steady-state current-voltage relationship was N-shaped with a region of negative slope conductance between −50 mV and −20 mV. The rate of inactivation varied according to the holding potential and the command potential. The inward currents were maintained when external Ca²⁺ was replaced by Ba²⁺, and were blocked by Cd²⁺, suggesting that Ca²⁺ was the principal charge carrier. The results demonstrate the existence of calcium current in olfactory cortex neurones.