EFFECTS OF HYPOSMOLAR SOLUTIONS ON MEMBRANE CURRENTS OF HIPPOCAMPAL INTERNEURONS AND MOSSY CELLS IN-VITRO

Whole cell voltage-clamp recordings in rat hippocampal slices were use d to investigate the effect of changes in extracellular osmolarity on voltage-activated potassium currents. Currents were evoked from oriens /alveus (O/A) interneurons, hilar interneurons, and mossy cells. Hypos molar external solutions produced a significant potentiation of K+ cur rent recorded from O/A and hilar interneurons, but not from mossy cell s. Hyposmolar solutions also dramatically potentiated the spontaneous excitatory postsynaptic currents recorded from mossy cells. These resu lts suggest that hippocampal excitability can be modulated by the comp lex actions exerted by changes in extracellular osmolarity.