title: Characterization of sodium currents in mammalian sensory neurons cultured in serum-free defined medium with and without nerve growth factor.
abstract: The influence of nerve growth factor (NGF) on Na currents of rat dorsal root ganglia (DRG) was studied in neurons obtained from newborns and cultured for 2-30 hr in serum-free defined medium (SFM). Cell survival for the period studied was 78-87% both with and without NGF. Na currents were detected in all cells cultured for 6-9 hr. They were also detected after 2 hr in culture in 21.5% of the cells cultured without NGF (-NGF cells), and in 91.5% of the cells cultured with NGF (+NGF cells). Current density of the -NGF cells was 2.3 and 2 pA/microns 2 after growth for 2 and 6-9 hr, respectively, compared to 3.0 and 3.9 pA/microns 2 for the +NGF cells. The +NGF cells were separated into fast (F), Intermediate (I) and slow (S) cells, based on the Na current they expressed, while -NGF cells were all of the I type. F, I and S currents differed in their voltage-dependent inactivation (Vh50 = -79, -28 and -20 mV), kinetics of inactivation (tau h = 0.55, 1.3 and 7.75 msec), and TTX sensitivity (Ki = 60, 550 and 1100 nM). All currents were depressed by [Ca]0 with a KdCa of 22, 17 and 8 mM for F, I and S currents, respectively. Current density of F and S currents was 5.5 and 5 pA/micron 2 for the I current. The concentration-dependent curve of I current vs. TTX indicated that I current has two sites: one with F-like and another with S-like Ki for TTX. Hybridization of F and S currents yielded I-like currents. Thus, the major effect of NGF on Na currents in SFM is the acceleration of Na current acquisition and diversity, reflected in an increase of either the S or F type in a cell.
authors.affiliation: Department of Physiology and Biophysics, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa.
authors.forename: G
authors.initials: G
authors.lastname: Omri
authors.forename: H
authors.initials: H
authors.lastname: Meiri
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media; D004553:Electric Conductivity; D005727:Ganglia, Spinal / Q000378:metabolism*; D007700:Kinetics; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009475:Neurons, Afferent / Q000378:metabolism*; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
chemical_list: D003470:Culture Media; D009414:Nerve Growth Factors; D015222:Sodium Channels; D013779:Tetrodotoxin; D002118:Calcium