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Presynaptic inhibition of pre‐Bötzinger complex neurons in high calcium and disturbed seizure‐like inspiratory bursting in low calcium in newborn rat brainstem slices
Author(s) -
Ruangkittisakul Araya,
Panaitescu Bogdan,
Bornes Troy D,
Ballanyi Klaus
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.960.3
Subject(s) - bursting , brainstem , extracellular , calcium , postsynaptic potential , electrophysiology , rhythm , biology , anatomy , medicine , neuroscience , biophysics , microbiology and biotechnology , receptor
Inspiratory pre‐Bötzinger complex (preBötC) rhythm in brainstem slices in physiological (3mM) K + is depressed by raising superfusate Ca 2+ from 1mM to 1.5mM. Here, we studied cellular mechanisms of such Ca 2+ block of preBötC rhythm and quantified extracellular preBötC interneuron and preBötC‐driven hypoglossal (XII) motoneuron responses to varied Ca 2+ and Mg 2+ . In 400µm thick newborn rat brainstem slices, preBötC/XII rhythm stopped after <2h in 3K + ‐1.2Ca 2+ , but was restored in 7mM K + . Stable preBötC/XII rhythm in 7K + ‐1.2Ca 2+ was blocked by 2‐3mM Ca 2+ without effect on resting potential or input resistance of preBötC and non‐preBötC inspiratory neurons or tonic neurons. preBötC/XII burst rates increased while amplitudes decreased in <1.2Ca 2+ until rhythms stopped in <0.25Ca 2+ . =0.8mM Ca 2+ evoked seizure‐like activity, partially masking inspiratory XII bursts. Lowering Mg 2+ from 1mM to 0.25mM in 7K + ‐1.2Ca 2+ did not affect preBötC/XII rhythms, whereas 3mM Mg 2+ depressed their rate and amplitude to 43% and 82% of control, respectively. Findings show that inspiratory interneuron and XII motoneuron networks in brainstem slices are relatively insensitive to extracellular Mg 2+ , but generate stable rhythm only in 0.8‐1.2mM Ca 2+ . Lack of postsynaptic membrane effects suggests that Ca 2+ block of isolated preBötC networks involves primarily presynaptic mechanisms. Supported by CIHR‐MFN, CIHR, AHFMR.