TY - JOUR
T1 - Differential roles of ionotropic glutamate receptors in canine medullary inspiratory neurons of the ventral respiratory group
AU - Krolo, M.
AU - Stuth, E. A.
AU - Tonkovic-Capin, M.
AU - Dogas, Z.
AU - Hopp, F. A.
AU - McCrimmon, D. R.
AU - Zuperku, E. J.
PY - 1999
Y1 - 1999
N2 - The relative roles of ionotropic N-methyl-D-aspartate (NMDA) and non- NMDA glutamate receptors in supplying excitatory drive to inspiratory (I) augmenting pattern neurons of the ventral respiratory group were studied in anesthetized, ventilated, paralyzed, and vagotomized dogs. Multibarrel micropipettes were used to record simultaneously single-unit neuronal activity and pressure microeject the NMDA antagonist, 2-amino-5- phosphonovalerate (AP5; 2 mM), the non-NMDA antagonist 2,3-dihydroxy-6- nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX; 0.25 mM), and an artificial cerebrospinal fluid vehicle. Ejected volume-rates were measured directly via meniscus level changes. The moving time average of phrenic nerve activity was used to determine respiratory phase durations and to synchronize cycle- triggered histograms of the discharge patterns. Both AP5 and NBQX produced dose-dependent reductions in peak spontaneous I neuronal discharge frequency (F(n)). The average (± SE) maximum reduction in peak F(n) produced by AP5 was 69.1 ± 4.2% and by NBQX was 47.1 ≠ 3.3%. Blockade of both glutamate receptor subtypes nearly silenced these neurons, suggesting that their activity is highly dependent on excitatory synaptic drive mediated by ionotropic glutamate receptors. Differential effects were found for the two glutamatergic antagonists. AP5 produced downward, parallel shifts in the augmenting pattern of discharge, whereas NBQX reduced the slope of the augmenting discharge pattern. These results suggest that time-varying excitatory input patterns to the canine I bulbospinal neurons are mediated by non-NMDA glutamate receptors and that constant or tonic input patterns to these neurons are mediated by NMDA receptors.
AB - The relative roles of ionotropic N-methyl-D-aspartate (NMDA) and non- NMDA glutamate receptors in supplying excitatory drive to inspiratory (I) augmenting pattern neurons of the ventral respiratory group were studied in anesthetized, ventilated, paralyzed, and vagotomized dogs. Multibarrel micropipettes were used to record simultaneously single-unit neuronal activity and pressure microeject the NMDA antagonist, 2-amino-5- phosphonovalerate (AP5; 2 mM), the non-NMDA antagonist 2,3-dihydroxy-6- nitro-7-sulfamoyl-benzo(f)quinoxaline (NBQX; 0.25 mM), and an artificial cerebrospinal fluid vehicle. Ejected volume-rates were measured directly via meniscus level changes. The moving time average of phrenic nerve activity was used to determine respiratory phase durations and to synchronize cycle- triggered histograms of the discharge patterns. Both AP5 and NBQX produced dose-dependent reductions in peak spontaneous I neuronal discharge frequency (F(n)). The average (± SE) maximum reduction in peak F(n) produced by AP5 was 69.1 ± 4.2% and by NBQX was 47.1 ≠ 3.3%. Blockade of both glutamate receptor subtypes nearly silenced these neurons, suggesting that their activity is highly dependent on excitatory synaptic drive mediated by ionotropic glutamate receptors. Differential effects were found for the two glutamatergic antagonists. AP5 produced downward, parallel shifts in the augmenting pattern of discharge, whereas NBQX reduced the slope of the augmenting discharge pattern. These results suggest that time-varying excitatory input patterns to the canine I bulbospinal neurons are mediated by non-NMDA glutamate receptors and that constant or tonic input patterns to these neurons are mediated by NMDA receptors.
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U2 - 10.1152/jn.1999.82.1.60
DO - 10.1152/jn.1999.82.1.60
M3 - Article
C2 - 10400935
AN - SCOPUS:0032771345
SN - 0022-3077
VL - 82
SP - 60
EP - 68
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 1
ER -