A metabolically stable analog of 1,4,5-inositol trisphosphate activates a novel K + conductance in pyramidal cells of the rat hippocampal slice

Abstract

IP(s) 3, a metabolically stable analog of 1,4,5-inositol trisphosphate ON, inhibited action potential firing when injected into hippocampal pyramidal cells. This effect was associated with decreased input resistance, a more negative resting potential, outward rectification at depolarized potentials, and an afterhyperpolarization. The response to IP(s) 3, was unaffected by antagonists of Na +, Cat +, and Cl - conductances, but was sensitive to changes in extracellular K + concentration. The IP(s) 3-induced conductance was voltage-dependent, was activated in 10 ms with depolarization, and was blocked by extracellular Bat + or intracellular Cat + chelation. It was not suppressed by other K + conductance antagonists. Thus, IP(s) 3, may activate a novel K + conductance in CAI pyramidal cells. IP 3 itself did not elicit this conductance, suggesting it may be rapidly metabolized in these cells.