Glutamatergic inputs to the CVLM independent of the NTS promote tonic inhibition of sympathetic vasomotor tone in rats
| Autor: | Ann M. Schreihofer, Daniel A. Mandel |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Male
Nitroprusside medicine.medical_specialty Sympathetic nervous system Sympathetic Nervous System Time Factors Baroreceptor Microinjections Physiology Glutamine Blood Pressure Vagotomy Biology Baroreflex Kynurenic Acid Kynurenate Rats Sprague-Dawley Glutamatergic Physiology (medical) Internal medicine Neural Pathways Solitary Nucleus medicine Animals GABA Agonists Neurons Medulla Oblongata Muscimol Solitary nucleus Respiratory center Neural Inhibition Splanchnic Nerves Articles Rostral ventrolateral medulla Respiratory Center Rats body regions Disease Models Animal Endocrinology medicine.anatomical_structure nervous system Anesthesia Blood Vessels Hypotension Cardiology and Cardiovascular Medicine Excitatory Amino Acid Antagonists circulatory and respiratory physiology |
| Zdroj: | American Journal of Physiology-Heart and Circulatory Physiology. 295:H1772-H1779 |
| ISSN: | 1522-1539 0363-6135 |
| DOI: | 10.1152/ajpheart.216.2008 |
| Popis: | GABAergic neurons in the caudal ventrolateral medulla (CVLM) are driven by baroreceptor inputs relayed via the nucleus tractus solitarius (NTS), and they inhibit neurons in rostral ventrolateral medulla to reduce sympathetic nerve activity (SNA) and arterial pressure (AP). After arterial baroreceptor denervation or lesions of the NTS, inhibition of the CVLM continues to increase AP, suggesting additional inputs also tonically activate the CVLM. This study examined whether the NTS contributes to baroreceptor-independent drive to the CVLM and whether glutamate promotes baroreceptor- and NTS-independent activation of the CVLM to tonically reduce SNA. In addition, we evaluated whether altering central respiratory drive, a baroreceptor-independent regulator of CVLM neurons, influences glutamatergic inputs to the CVLM. Splanchnic SNA and AP were measured in chloralose-anesthetized, ventilated, paralyzed rats. The infusion of nitroprusside decreased AP below threshold for baroreceptor afferent firing (A agonist muscimol did not further increase SNA. In contrast, after inhibition of the NTS, blockade of glutamatergic inputs to CVLM by microinjection of kynurenate increased SNA (274 ± 54%; P < 0.05; n = 7). In vagotomized rats with baroreceptors unloaded, inhibition of glutamatergic inputs to CVLM evoked a larger rise in SNA when central respiratory drive was increased (219 ± 16% vs. 271 ± 17%; n = 5; P < 0.05). These data suggest that baroreceptor inputs provide the major drive for the NTS-mediated excitation of the CVLM. Furthermore, glutamate tonically activates the CVLM to reduce SNA independent of the NTS, and this excitatory input appears to be affected by the strength of central respiratory drive. |
| Databáze: | OpenAIRE |
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