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NMDA receptors in preBötzinger complex neurons can drive respiratory rhythm independent of AMPA receptors
Author(s) -
MorgadoValle Consuelo,
Feldman Jack L.
Publication year - 2007
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2007.130617
Subject(s) - nbqx , ampa receptor , nmda receptor , excitatory postsynaptic potential , postsynaptic potential , respiratory system , respiratory center , neuroscience , glutamate receptor , dizocilpine , receptor , chemistry , dnqx , biology , anesthesia , medicine , inhibitory postsynaptic potential
The role of AMPA receptors (AMPARs) in generation and propagation of respiratory rhythm is well documented both in vivo and in vitro , whereas the functional significance of NMDA receptors (NMDARs) in preBötzinger complex (preBötC) neurons has not been explored. Here we examined the interactions between AMPARs and NMDARs during spontaneous respiratory rhythm generation in slices from neonatal rats in vitro . We tested the hypothesis that activation of NMDARs can drive respiratory rhythm in the absence of other excitatory drives. Blockade of NMDARs with dizocilpine hydrogen maleate (MK‐801, 20 μ m ) had a negligible effect on respiratory rhythm and pattern under standard conditions in vitro , whereas blockade of AMPARs with NBQX (0.5 μ m ) completely abolished respiratory activity. Removal of extracellular Mg 2+ to relieve the voltage‐dependent block of NMDARs maintained respiratory rhythm without a significant effect on period, even in the presence of high NBQX concentrations (≤ 100 μ m ). Removal of Mg 2+ increased inspiratory‐modulated inward current peak ( I I ) and charge ( Q I ) in preBötC neurons voltage‐clamped at −60 mV by 245% and 309%, respectively, with respect to basal values. We conclude that the normal AMPAR‐mediated postsynaptic current underlying respiratory drive can be replaced by NMDAR‐mediated postsynaptic current when the voltage‐dependent Mg 2+ block is removed. Under this condition, respiratory‐related frequency is unaffected by changes in I I , suggesting that the two can be independently regulated.