Dialysis of inositol 1,4,5-trisphosphate induces inward currents and Ca2+ uptake in frog olfactory receptor cells

Frog olfactory receptor cells (Rana ridibunda) were isolated with an enzyme-free procedure and loaded with fura-2 from the patch pipette. The cells responded to superfusion with ''IP3-odorants'' with an inward current and an increase of the intracellular Ca2+ concentration, [Ca2+](i) An odorant-induced inward current and an increase in [Ca2+](i) were also observed while flooding cells with 1 mM cAMP from the pipette, a condition which drives the cAMP signal pathway into adaptation. Flooding of cells with 50 mu M IP3 from the pipette also induced an inward current with an increase in [Ca2+](i) in normal Ringer solution and an inward current without changes in [Ca2+](i) in Ca2+-free solution. The experiments suggest that IP3 activates a cation channel at the plasma membrane, allowing inflow of Na+ and Ca2+ ions. (C) 1996 Academic Press, Inc.