SUBTHRESHOLD MEMBRANE-POTENTIAL OSCILLATIONS IN IMMATURE RAT CA3 HIPPOCAMPAL-NEURONS

SUBTHRESHOLD membrane potential oscillations (MPOs) were recorded intr acellularly in 31 of 43 (>70%) immature CA3 hippocampal neurones (from 3-17 days postnatally). MPOs (3-5 mV, 3-15 Hz) occurred at resting me mbrane potential (RMP) in 20 of 31 neurones, or following depolarizati on (11 of 31 neurones); with sufficient depolarization spontaneous act ion potentials (APs) were generated from the positive-going phase of M POs. In all cells, MPOs were blocked by steady membrane hyperpolarizat ion. Tetrodotoxin abolished MPOs (n = 4); Co2+ markedly reduced them ( n = 3), and tetraethylammonium, added in the presence of TTX, revealed lower frequency oscillatory activity (n = 2). We conclude that subthr eshold MPOs in immature hippocampus, possibly linked to theta rhythm g eneration and memory acquisition, depend on voltage-dependent Na+ elec trogenesis and they might be additionally controlled by Ca2+ and K+ co nductances.