Excitatory amino acid receptors within NTS mediate arterial chemoreceptor reflexes in rats

W. Zhang, Steve Wayne Mifflin

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

The nucleus tractus solitarius (NTS) is the primary site of termination of arterial baroreceptor and chemoreceptor afferent fibers. Excitatory amino acid (EAA) receptors within NTS have been shown to play an important role in the mediation of arterial baroreceptor reflexes; however, the importance of EAA receptors within NTS in the mediation of arterial chemoreceptor reflexes remains controversial. Therefore, in chloralose-urethan-anesthetized, mechanically ventilated, paralyzed rats, 4 nmol of the broad-spectrum EAA receptor antagonist kynurenic acid (Kyn) was injected into the NTS to observe the effects of EAA receptor blockade on the pressor responses evoked by either activation of ipsilateral carotid body chemoreceptors (by close arterial injection of CO2-saturated bicarbonate) or electrical stimulation of ipsilateral carotid sinus nerve (CSN). Under control conditions, activation of carotid body chemoreceptors and CSN stimulation evoked increases in arterial pressure of 27 ± 2 (n = 24 sites) and 28 ± 3% (n = 8), respectively. Kyn microinjection into NTS significantly reduced the pressor responses evoked by activation of carotid body chemoreceptors and electrical stimulation of the CSN for 20 and 25 min, respectively. Attenuation of pressor responses evoked by chemoreceptor activation were maximal at 20 min post-Kyn injection (13 ± 2%), whereas CSN-evoked pressor responses were maximally attenuated at 15 min (6 ± 4%). Microinjection into NTS of 4 nmol of xanthurenic acid, a structural analogue of Kyn with no EAA receptor antagonist properties, had no effect on chemoreceptor reflexes. We conclude that EAA receptors within NTS play an important role in the mediation of arterial chemoreceptor reflexes.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume265
Issue number2 34-2
StatePublished - 1 Jan 1993

Fingerprint

Solitary Nucleus
Glutamate Receptors
Reflex
Kynurenic Acid
Carotid Sinus
Carotid Body
Excitatory Amino Acid Antagonists
Microinjections
Electric Stimulation
Chloralose
Pressoreceptors
Injections
Baroreflex
Urethane
Bicarbonates
Arterial Pressure

Keywords

  • brain stem
  • cardiovascular regulation
  • kynurenic acid

Cite this

@article{16b42a418fdd4c82bd84e0faa96bf6a7,
title = "Excitatory amino acid receptors within NTS mediate arterial chemoreceptor reflexes in rats",
abstract = "The nucleus tractus solitarius (NTS) is the primary site of termination of arterial baroreceptor and chemoreceptor afferent fibers. Excitatory amino acid (EAA) receptors within NTS have been shown to play an important role in the mediation of arterial baroreceptor reflexes; however, the importance of EAA receptors within NTS in the mediation of arterial chemoreceptor reflexes remains controversial. Therefore, in chloralose-urethan-anesthetized, mechanically ventilated, paralyzed rats, 4 nmol of the broad-spectrum EAA receptor antagonist kynurenic acid (Kyn) was injected into the NTS to observe the effects of EAA receptor blockade on the pressor responses evoked by either activation of ipsilateral carotid body chemoreceptors (by close arterial injection of CO2-saturated bicarbonate) or electrical stimulation of ipsilateral carotid sinus nerve (CSN). Under control conditions, activation of carotid body chemoreceptors and CSN stimulation evoked increases in arterial pressure of 27 ± 2 (n = 24 sites) and 28 ± 3{\%} (n = 8), respectively. Kyn microinjection into NTS significantly reduced the pressor responses evoked by activation of carotid body chemoreceptors and electrical stimulation of the CSN for 20 and 25 min, respectively. Attenuation of pressor responses evoked by chemoreceptor activation were maximal at 20 min post-Kyn injection (13 ± 2{\%}), whereas CSN-evoked pressor responses were maximally attenuated at 15 min (6 ± 4{\%}). Microinjection into NTS of 4 nmol of xanthurenic acid, a structural analogue of Kyn with no EAA receptor antagonist properties, had no effect on chemoreceptor reflexes. We conclude that EAA receptors within NTS play an important role in the mediation of arterial chemoreceptor reflexes.",
keywords = "brain stem, cardiovascular regulation, kynurenic acid",
author = "W. Zhang and Mifflin, {Steve Wayne}",
year = "1993",
month = "1",
day = "1",
language = "English",
volume = "265",
journal = "American Journal of Physiology - Heart and Circulatory Physiology",
issn = "0363-6135",
publisher = "American Physiological Society",
number = "2 34-2",

}

Excitatory amino acid receptors within NTS mediate arterial chemoreceptor reflexes in rats. / Zhang, W.; Mifflin, Steve Wayne.

In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 265, No. 2 34-2, 01.01.1993.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Excitatory amino acid receptors within NTS mediate arterial chemoreceptor reflexes in rats

AU - Zhang, W.

AU - Mifflin, Steve Wayne

PY - 1993/1/1

Y1 - 1993/1/1

N2 - The nucleus tractus solitarius (NTS) is the primary site of termination of arterial baroreceptor and chemoreceptor afferent fibers. Excitatory amino acid (EAA) receptors within NTS have been shown to play an important role in the mediation of arterial baroreceptor reflexes; however, the importance of EAA receptors within NTS in the mediation of arterial chemoreceptor reflexes remains controversial. Therefore, in chloralose-urethan-anesthetized, mechanically ventilated, paralyzed rats, 4 nmol of the broad-spectrum EAA receptor antagonist kynurenic acid (Kyn) was injected into the NTS to observe the effects of EAA receptor blockade on the pressor responses evoked by either activation of ipsilateral carotid body chemoreceptors (by close arterial injection of CO2-saturated bicarbonate) or electrical stimulation of ipsilateral carotid sinus nerve (CSN). Under control conditions, activation of carotid body chemoreceptors and CSN stimulation evoked increases in arterial pressure of 27 ± 2 (n = 24 sites) and 28 ± 3% (n = 8), respectively. Kyn microinjection into NTS significantly reduced the pressor responses evoked by activation of carotid body chemoreceptors and electrical stimulation of the CSN for 20 and 25 min, respectively. Attenuation of pressor responses evoked by chemoreceptor activation were maximal at 20 min post-Kyn injection (13 ± 2%), whereas CSN-evoked pressor responses were maximally attenuated at 15 min (6 ± 4%). Microinjection into NTS of 4 nmol of xanthurenic acid, a structural analogue of Kyn with no EAA receptor antagonist properties, had no effect on chemoreceptor reflexes. We conclude that EAA receptors within NTS play an important role in the mediation of arterial chemoreceptor reflexes.

AB - The nucleus tractus solitarius (NTS) is the primary site of termination of arterial baroreceptor and chemoreceptor afferent fibers. Excitatory amino acid (EAA) receptors within NTS have been shown to play an important role in the mediation of arterial baroreceptor reflexes; however, the importance of EAA receptors within NTS in the mediation of arterial chemoreceptor reflexes remains controversial. Therefore, in chloralose-urethan-anesthetized, mechanically ventilated, paralyzed rats, 4 nmol of the broad-spectrum EAA receptor antagonist kynurenic acid (Kyn) was injected into the NTS to observe the effects of EAA receptor blockade on the pressor responses evoked by either activation of ipsilateral carotid body chemoreceptors (by close arterial injection of CO2-saturated bicarbonate) or electrical stimulation of ipsilateral carotid sinus nerve (CSN). Under control conditions, activation of carotid body chemoreceptors and CSN stimulation evoked increases in arterial pressure of 27 ± 2 (n = 24 sites) and 28 ± 3% (n = 8), respectively. Kyn microinjection into NTS significantly reduced the pressor responses evoked by activation of carotid body chemoreceptors and electrical stimulation of the CSN for 20 and 25 min, respectively. Attenuation of pressor responses evoked by chemoreceptor activation were maximal at 20 min post-Kyn injection (13 ± 2%), whereas CSN-evoked pressor responses were maximally attenuated at 15 min (6 ± 4%). Microinjection into NTS of 4 nmol of xanthurenic acid, a structural analogue of Kyn with no EAA receptor antagonist properties, had no effect on chemoreceptor reflexes. We conclude that EAA receptors within NTS play an important role in the mediation of arterial chemoreceptor reflexes.

KW - brain stem

KW - cardiovascular regulation

KW - kynurenic acid

UR - http://www.scopus.com/inward/record.url?scp=0027181136&partnerID=8YFLogxK

M3 - Article

C2 - 8368379

AN - SCOPUS:0027181136

VL - 265

JO - American Journal of Physiology - Heart and Circulatory Physiology

JF - American Journal of Physiology - Heart and Circulatory Physiology

SN - 0363-6135

IS - 2 34-2

ER -