Differential roles of ionotropic glutamate receptors in canine medullary inspiratory neurons of the ventral respiratory group. J Neurophysiol 1999 Jul;82(1):60-8
Date
07/13/1999Pubmed ID
10400935DOI
10.1152/jn.1999.82.1.60Scopus ID
2-s2.0-0032771345 (requires institutional sign-in at Scopus site) 33 CitationsAbstract
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 (Fn). The average (+/- SE) maximum reduction in peak Fn 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.
Author List
Krolo M, Stuth EA, Tonkovic-Capin M, Dogas Z, Hopp FA, McCrimmon DR, Zuperku EJAuthors
Eckehard A. Stuth MD Professor in the Anesthesiology department at Medical College of WisconsinEdward J. Zuperku PhD Professor in the Anesthesiology department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
2-Amino-5-phosphonovalerateAnimals
Dogs
Excitatory Amino Acid Antagonists
Female
Inhalation
Male
Medulla Oblongata
Membrane Potentials
Microinjections
N-Methylaspartate
Neurons
Quinoxalines
Receptors, Glutamate
Receptors, N-Methyl-D-Aspartate
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
