Calcium-dependent action potentials in guinea-pig olfactory cortex neurones.
Ca2+-dependent action potentials were recorded in guinea pig olfactory neurones in vitro (23 degrees--25 degrees C). In most cells (in the presence of tetrodotoxin: TTX) the current-voltage relationship displayed 'anomalous' rectification (apparent high slope resistance) at potentials approximately 20 mV depolarized to the resting membrane potential (approximately -80 mV) and strong outward rectification at more positive potentials. Intracellular Cs+-loading blocked outward rectification and increased action potential duration. Such spikes were TTX-insensitive and were further prolonged by external addition of tetraethylammonium (TEA) or Ba2+. Spikes recorded from Cs+-loaded, TTX/TEA-treated neurones displayed a prolonged plateau and an after-depolarization. They persisted when Ba2+ or Sr2+ were substituted for external Ca2+, but not when Mg2+ was the sole extracellular divalent cation. The spikes were blocked in the presence of Cd2+ but persisted when 82% of the extracellular Na+ was substituted by choline. A TTX-insensitive, slowly inactivating inward current at depolarized potentials is believed to account for the subthreshold 'anomalous' rectification and prolonged spike plateau.
D000085:Acetates; D019342:Acetic Acid; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002490:Central Nervous System / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000502:physiology*; D002586:Cesium; D002712:Chlorides; D004566:Electrodes; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009474:Neurons / Q000502:physiology*; D009833:Olfactory Pathways / Q000166:cytology / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D000085:Acetates; D002712:Chlorides; D013757:Tetraethylammonium Compounds; D002586:Cesium; D013779:Tetrodotoxin; D019789:Tetraethylammonium; C028019:cesium chloride; D019342:Acetic Acid; D002118:Calcium