Post-cultured development of basic electrophysiological properties of spinal neurons obtained from rat embryo

Basic electrical profiles of cultured neurons are modified by multiple fact ors, such as cell growth, differentiation and cell damage from the isolatio n procedure. In the present study, we assessed development of electrophysio logical properties of rat spinal neurons over the late embryonic and early postnatal period in a neuron-enriched culture. After recovery from acute da mage within 2 days after plating, the input conductance and amplitudes of v oltage-gated Na+ and K+ currents increased parallel to the increase in the cell capacitance. Whether this depended on the period or the growth of the cell area was estimated by normalizing the parameters with the cell capacit ance. The input conductance per unit area, the membrane time constant and t he Na+ current density remained constant for two weeks. However, densities of two types of outward K+ currents, an A-current and a delayed rectifier, required 3-5 days to reach the maximum, although neither thresholds for act ivation nor sensitivities to blockers (TEA and 4AP) altered. The hyperpolar izing shift of the resting membrane potential became stabilized within 6-8 days, suggesting that the development of the K+ currents underlay the shift . These results show that passive electrical properties and voltage-gated c urrents of rat spinal neurons in the neuron-rich culture differ in temporal patterns of development but stabilize at the latest within a week, corresp onding to the day of birth. (C) 2001 Elsevier Science B.V. All rights reser ved.