Chronic Intermittent Hypoxia Alters Nmda and Ampa-evoked Currents in Nts Neurons Receiving Carotid Body Chemoreceptor Inputs.
From: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA. mifflin@uthscsa.edu
American journal of physiology. Regulatory, integrative and comparative physiology
- Publish Date: Jun 2007
- ISSN: 0363-6119
- Volume: 292
- Issue: 6
- Pages: R2259-65
- Medium: Print
- Language: English
- Citation (JAMA): de Paula Patricia M, Tolstykh Gleb, Mifflin Steve, et al. Chronic Intermittent Hypoxia Alters Nmda and Ampa-evoked Currents in Nts Neurons Receiving Carotid Body Chemoreceptor Inputs.. Am. J. Physiol. Regul. Integr. Comp. Physiol. Jun 2007;292:R2259-65
Abstract
Chronic exposure to intermittent hypoxia (CIH) has been used in animals to mimic the arterial hypoxemia that accompanies sleep apnea. Humans with sleep apnea and animals exposed to CIH have elevated blood pressures and augmented sympathetic nervous system responses to acute exposures to hypoxia. To test the hypothesis that exposure to CIH alters neurons within the nucleus of the solitary tract (NTS) that integrate arterial chemoreceptor afferent inputs, we measured whole cell currents induced by activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors in enzymatically dispersed NTS neurons from normoxic (NORM) and CIH-exposed rats (alternating cycles of 3 min at 10% O2 followed by 3 min at 21% O2 between 8 AM and 4 PM for 7 days). To identify NTS neurons receiving carotid body afferent inputs the anterograde tracer 4- (4-(dihexadecylamino)styryl-N-methylpyridinum iodide (DiA) was placed onto the carotid body 1 wk before exposure to CIH. AMPA dose-response curves had similar EC50 but maximal responses increased in neurons isolated from DiA-labeled CIH (20.1 +/- 0.8 microM, n = 9) compared with NORM (6.0 +/- 0.3 microM, n = 8) rats. NMDA dose-response curves also had similar EC50 but maximal responses decreased in CIH (8.4 +/- 0.4 microM, n = 8) compared with NORM (19.4 +/- 0.6 microM, n = 9) rats. These results suggest reciprocal changes in the number and/or conductance characteristics of AMPA and NMDA receptors. Enhanced responses to AMPA receptor activation could contribute to enhanced chemoreflex responses observed in animals exposed to CIH and humans with sleep apnea.
Mesh Headings (Keywords): Afferent Pathways, Animals, Carotid Body, Cells, Cultured, Chemoreceptors, Dose-Response Relationship, Drug, Evoked Potentials, Male, N-Methylaspartate, Rats, Rats, Sprague-Dawley, Solitary Nucleus, alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
Check for Full Text / PubMed Unique Identifier (PMID): 17332161
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