Potassium Currents in Precursor Cells Isolated From the Anterior Subventricular Zone of the Neonatal Rat Forebrain

• Published in: Journal of neurophysiology 1999-01, Vol.81 (1), p.95-102
• Main Authors: Stewart, R. R, Zigova, T, Luskin, M. B
• Format: Article
• Language: English
• Subjects: Animals; Animals, Newborn - physiology; Cerebral Ventricles - cytology; Cerebral Ventricles - metabolism; Delayed Rectifier Potassium Channels; Electric Stimulation; Electrophysiology; Membrane Potentials - physiology; Patch-Clamp Techniques; Potassium Channels - metabolism; Potassium Channels, Voltage-Gated; Prosencephalon - cytology; Prosencephalon - metabolism; Rats; Tetraethylammonium Compounds - pharmacology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.1999.81.1.95

R. R. Stewart 1 , T. Zigova 2 , and M. B. Luskin 2 1  Laboratory of Molecular and Cellular Neurobiology, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-8115; and 2  Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322-3030 Stewart, R. R., T. Zigova, and M. B. Luskin . Potassium currents in precursor cells isolated from the anterior subventricular zone of the neonatal rat forebrain. J. Neurophysiol. 81: 95-102, 1999. The progenitor cells from the anterior part of the neonatal subventricular zone, the SVZa, are unusual in that, although they undergo division, they have a neuronal phenotype. To characterize the electrophysiological properties of the SVZa precursor cells, recordings were made of potassium and sodium currents from SVZa cells that were removed from postnatal day 0-1 rats and cultured for 1 day. The properties of the delayed rectifier and A-type potassium currents were described by classical Hodgkin and Huxley analyses of activation and inactivation. In addition, cells were assessed under current clamp for their ability to generate action potentials. The A-type potassium current ( I K(A) ) was completely inactivated at a holding potential of 50 mV. The remaining potassium current resembled the delayed rectifier current ( I K(DR) ) in that it was blocked by tetraethylammonium (TEA; IC 50 4.1 mM) and activated and inactivated slowly compared with I K(A) . The conductance-voltage ( G - V ) curve revealed that G increased continuously from 0.2 nS at 40 mV to a peak of 2.6 nS at +10 or +20 mV, and then decreased for voltages above +30 mV. Activation time constants were largest at 40 mV (~11 ms) and smallest at 100 mV (~1.5 ms). The properties of I K(A) were studied in the presence of 20 mM TEA, to block I K(DR) , and from a holding potential of 15 mV, to inactivate both I K(DR) and I K(A) . I K(A) was then allowed to recover from inactivation to negative potentials during 200- to 800-ms pulses. Recovery from inactivation was fastest at 130 mV (~21 ms) and slowest at 90 mV (~135 ms). Inactivation was voltage independent from 60 to +60 mV with a time constant of ~15 ms. At steady state, I K(A) was half inactivated at 90 mV. G K(A) increased from 0.2 nS at 60 mV to a peak of 2.4 nS at +40 mV. Finally, the activation time constants ranged from ~1.9 ms at 50 mV to 0.7 ms at +60 mV. The properties of I K(A) resembled those of I K(A) found in differentiating cerebellar granule neurons. Most SVZ