Na+ current kinetics are not the determinants of the action potential duration in neurons of the rat ventral tegmental area.
Na+ currents were recorded from two morphological subpopulations of neurons acutely dissociated from the rat ventral tegmental area (VTA). About 45% of 56 VTA cells examined possessed only the ordinary type of Na+ current which was blocked by a low concentration (0.2 microM) of TTX. However, the remaining 55% had the Na+ current which contained a small fraction of the TTX-insensitive component, irrespective of morphological variations and action potential durations of VTA cells. The peak amplitude of the TTX-insensitive component was less than 10% of the peak amplitude of the total Na+ current. The activation and inactivation kinetics of the TTX-insensitive component were much the same as those of the overwhelming TTX-sensitive component of the Na+ current in VTA cells but differed from those of the TTX-insensitive Na+ current reported in peripheral sensory neurons. Thus, it was concluded that the well-known different action potential durations found for subpopulations of VTA cells are not due to multiplicity of Na+ channel kinetics.
Ogata
N
N
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Tatebayashi
H
H
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D004298:Dopamine / Q000378:metabolism / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009474:Neurons / Q000502:physiology*; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism*; D013681:Tegmentum Mesencephali / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015222:Sodium Channels; D013779:Tetrodotoxin; D004298:Dopamine