Faculty Collaboration Database

Breathing of awake goats during prolonged dysfunction of caudal M ventrolateral medullary neurons. J Appl Physiol (1985) 1998 Jan;84(1):129-40

Date

02/06/1998

Pubmed ID

9451627

DOI

10.1152/jappl.1998.84.1.129

Scopus ID

2-s2.0-0031884302 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

Cooling the caudal M ventrolateral medullary (VLM) surface for 30 s results in a sustained apnea in anesthetized goats but only a 30% decrease in breathing in awake goats. The purpose of the present study was to determine, in the awake state, the effect of prolonged (minutes, hours) caudal M neuronal dysfunction on eupneic breathing and CO2 sensitivity. Dysfunction was created by ejecting excitatory amino acid receptor antagonists or a neurotoxin on the VLM surface through guide tubes chronically implanted bilaterally on a 10- to 12-mm2 portion of the caudal M VLM surface of 12 goats. Unilateral and bilateral ejections (1 microliter) of selective antagonists for N-methyl-D-aspartic acid or non-N-methyl-D-aspartic acid receptors had no significant effect on eupneic breathing or CO2 sensitivity. Unilateral ejection of a nonselective excitatory amino acid receptor antagonist generally had no effect on eupneic breathing or CO2 sensitivity. However, bilateral ejection of this antagonist resulted in a significant 2-Torr hypoventilation during eupnea and a significant reduction in CO2 sensitivity to 60 +/- 9% of control. Unilateral ejection of the neurotoxin kainic acid initially stimulated breathing; however, breathing then returned to near control with no incidence of apnea. After the kainic acid ejection, CO2 sensitivity was reduced significantly to 60 +/- 7% of control. We conclude that in the awake state a prolonged dysfunction of caudal M VLM neurons results in compensation by other mechanisms (e.g., carotid chemoreceptors, wakefulness) to maintain near-normal eupneic breathing, but compensation is more limited for maintaining CO2 sensitivity.

Author List

Forster HV, Pan LG, Lowry TF, Feroah T, Gershan WM, Whaley AA, Forster MM, Sprtel B

Author

Hubert V. Forster PhD Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Carbon Dioxide
Cold Temperature
Excitatory Amino Acid Agonists
Excitatory Amino Acid Antagonists
Female
Goats
Kainic Acid
Male
Medulla Oblongata
N-Methylaspartate
Neurons
Neurotoxins
Receptors, N-Methyl-D-Aspartate
Respiratory Mechanics
alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid