title: Inhibitory ryanodine prevents ryanodine receptor-mediated Ca²⁺ release without affecting endoplasmic reticulum Ca²⁺ content in primary hippocampal neurons.
abstract: Ryanodine is a cell permeant plant alkaloid that binds selectively and with high affinity to ryanodine receptor (RyR) Ca(2+) release channels. Sub-micromolar ryanodine concentrations activate RyR channels while micromolar concentrations are inhibitory. Several reports indicate that neuronal synaptic plasticity, learning and memory require RyR-mediated Ca(2+)-release, which is essential for muscle contraction. The use of micromolar (inhibitory) ryanodine represents a common strategy to suppress RyR activity in neuronal cells: however, micromolar ryanodine promotes RyR-mediated Ca(2+) release and endoplasmic reticulum Ca(2+) depletion in muscle cells. Information is lacking in this regard in neuronal cells; hence, we examined here if addition of inhibitory ryanodine elicited Ca(2+) release in primary hippocampal neurons, and if prolonged incubation of primary hippocampal cultures with inhibitory ryanodine affected neuronal ER calcium content. Our results indicate that inhibitory ryanodine does not cause Ca(2+) release from the ER in primary hippocampal neurons, even though ryanodine diffusion should produce initially low intracellular concentrations, within the RyR activation range. Moreover, neurons treated for 1 h with inhibitory ryanodine had comparable Ca(2+) levels as control neurons. These combined findings imply that prolonged incubation with inhibitory ryanodine, which effectively abolishes RyR-mediated Ca(2+) release, preserves ER Ca(2+) levels and thus constitutes a sound strategy to suppress neuronal RyR function.
authors.affiliation: Biomedical Neuroscience Institute and Centro de Estudios Moleculares de la Célula, Faculty of Medicine, Universidad de Chile, Santiago, Chile.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Adasme
authors.affiliation: Biomedical Neuroscience Institute and Centro de Estudios Moleculares de la Célula, Faculty of Medicine, Universidad de Chile, Santiago, Chile; Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile.
authors.forename: Andrea
authors.initials: A
authors.lastname: Paula-Lima
authors.affiliation: Biomedical Neuroscience Institute and Centro de Estudios Moleculares de la Célula, Faculty of Medicine, Universidad de Chile, Santiago, Chile; Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Chile. Electronic address: chidalgo@med.uchile.cl.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hidalgo
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D061207:Calcium Ionophores / Q000494:pharmacology; D002478:Cells, Cultured; D003408:Cresols / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D012433:Ryanodine / Q000819:agonists / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D061207:Calcium Ionophores; D003408:Cresols; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; C006984:chlorocresol; D015759:Ionomycin; D019284:Thapsigargin; D002118:Calcium
keywords: Ca(2+) signaling; Hippocampus; Neuronal RyR function; Thapsigargin