Sodium current in periglomerular cells of frog olfactory bulb in vitro.
Kinetic properties of the sodium current in periglomerular (PG) cells were investigated by applying whole-cell patch-clamp techniques to thin slices of the frog olfactory bulb. Eight of the cells were intracellularly stained with Lucifer Yellow for precise identification. Under current-clamp conditions PG cells showed rich spontaneous activity at rest. Na current was isolated from other current contributions by equimolar substitution of K+ with Cs+ in the intracellular solution to prevent K-currents, and 100 microM Cd2+ in the external solution to block Ca-current. Depolarisations beyond -40 mV activated a fast transient TTX-sensitive inward current. Once activated, INa declined exponentially to zero following a single exponential. The underlying conductance showed a sigmoidal activation between -40 and +30 mV, with half activation at -17.4 mV and a maximal value of 9.7 nS per neurone. The steady-state inactivation was complete at -30 mV and completely removed at -90 mV, with a midpoint at -56 mV. The activation process could be adequately described by third order kinetics, with time constants ranging from 260 microseconds at -20 mV to 70 microseconds at +50 mV.
Bardoni
R
R
Dipartimento di Scienze Biomediche, Modena, Italy.
Magherini
P C
PC
Belluzzi
O
O
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009830:Olfactory Bulb / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011893:Rana esculenta; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D002104:Cadmium; D002586:Cesium; D013779:Tetrodotoxin