Relative magnitude of tonic and phasic synaptic excitation of medullary inspiratory neurons in dogs. Am J Physiol Regul Integr Comp Physiol 2000 Aug;279(2):R639-49
Date
08/12/2000Pubmed ID
10938255DOI
10.1152/ajpregu.2000.279.2.R639Scopus ID
2-s2.0-0033859199 (requires institutional sign-in at Scopus site) 34 CitationsAbstract
The relative contribution of phasic and tonic excitatory synaptic drives to the augmenting discharge patterns of inspiratory (I) neurons within the ventral respiratory group (VRG) was studied in anesthetized, ventilated, paralyzed, and vagotomized dogs. Multibarrel micropipettes were used to record simultaneously single-unit neuronal activity and pressure microejected antagonists of GABAergic, glycinergic, N-methyl-D-aspartate (NMDA) and non-NMDA glutamatergic, and cholinergic receptors. The discharge patterns were quantified via cycle-trigger histograms. The findings suggest that two-thirds of the excitatory drive to caudal VRG I neurons is tonic and mediated by NMDA receptors and the other third is ramp-like phasic and mediated by non-NMDA receptors. Cholinergic receptors do not appear to be involved. The silent expiratory phase is produced by phasic inhibition of the tonic activity, and approximately 80% of this inhibition is mediated by gamma-aminobutyric acid receptors (GABA(A)) and approximately 20% by glycine receptors. Phasic I inhibition by the I decrementing neurons does not appear to contribute to the predominantly step-ramp patterns of these I neurons. However, this decrementing inhibition may be very prominent in controlling the rate of augmentation in late-onset I neurons and those with ramp patterns lacking the step component.
Author List
Krolo M, Stuth EA, Tonkovic-Capin M, 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-phosphonovalerateAcetylcholine
Animals
Dogs
Excitatory Amino Acid Antagonists
Female
GABA Antagonists
Glycine Agents
Male
Medulla Oblongata
Neurons
Picrotoxin
Quinoxalines
Respiratory Physiological Phenomena
Strychnine
Synapses
