title: Non-stimulated Ca2+ leak pathway in cerebellar granule neurones.
abstract: The aim of this study was to investigate the pathways of calcium influx routes in non-stimulated cerebellar granule neurones by use of standard microspectrofluorimetric techniques. Repetitive application of Ca2+-free solutions for various time intervals induced decreases of resting cytosolic free Ca2+ concentration ([Ca2+]i) which were followed, on Ca2+ readmission, by a full recovery, always to the initial resting [Ca2+]i levels. Use of drugs to deplete calcium stores (thapsigargin, alone or combined with low levels of ionomycin) did not cause release of Ca2+ from the intracellular stores nor enhanced the activity of the Ca2+ entry pathway. This influx was mainly independent of voltage operated calcium channels, since both L-type channel blockers (nitrendipine) and the hyperpolarizing agent pinacidil (a K+-channel opener) were without effect. Contribution from glutamate receptors to this influx was eliminated since a combination of blockers of NMDA and AMPA glutamate receptors (NBQX and D-AP5) did not affect the properties of the Ca2+ response. The Ca2+ leak pathway was sensitive to micromolar levels of lanthanum and gadolinium, and to the compound 2-APB, features shared by several channels of the TRP superfamily. In summary, our results show the presence of a Ca2+ permeable pathway, active and patent in resting conditions in cerebellar granule neurones, and which is different from the voltage-operated calcium channels and not operated by depletion of the stores.
authors: Department of Physiology, University of Extremadura, Fac Vet Sci and Nursing School, 10071 Cáceres, Spain.
authors: P J Gómez
authors: PJ
authors: Pinilla
authors: A T
authors: AT
authors: Hernández
authors: M C
authors: MC
authors: Camello
authors: M J
authors: MJ
authors: Pozo
authors: E C
authors: EC
authors: Toescu
authors: P J
authors: PJ
authors: Camello
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D028581:Lanthanoid Series Elements / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D028581:Lanthanoid Series Elements; D019284:Thapsigargin; D002118:Calcium