IP3-activated calcium-permeable channels in the inside-out patches of cultured cerebellar Purkinje cells.
Inositol-1,4,5-trisphosphate (IP3)-activated calcium-permeable channels were recorded from inside-out patches of cultured cerebellar Purkinje cells. When 2-5 microM of IP3 was applied to the internal surface of the inside-out patches, inward Ba2+ currents were activated within 10 sec following the application in 11 out of 24 patches. In the presence of heparin (100 micrograms/ml), activation of Ba2+ currents by IP3 was inhibited. Unitary currents with different amplitudes and kinetics were observed; small and large unitary currents, and rapid fluctuations with various amplitudes. The small unitary currents (single channel conductance; 5.6 pS) were most frequent. Addition of inositol 1,3,4-trisphosphate (2-5 microM) slightly activated Ba2+ currents in 2 out of 10 patches, but the amount of the increment was much smaller than that produced by IP3. These results suggest a possibility that IP3 directly activates Ca(2+)-permeable channels in the plasma membrane of cerebellar Purkinje cells.
Kuno
M
M
Department of Physiology, Osaka City University Medical School, Japan.
Maeda
N
N
Mikoshiba
K
K
D000818:Animals; D000831:Animals, Newborn; D017609:Barium Compounds / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D007700:Kinetics; D015636:Magnesium Chloride / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008815:Mice, Inbred Strains; D011689:Purkinje Cells / Q000187:drug effects / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D017609:Barium Compounds; D015220:Calcium Channels; D002712:Chlorides; D015636:Magnesium Chloride; C024986:barium chloride; D013779:Tetrodotoxin; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002122:Calcium Chloride