Activation of GABAA but not GABAB receptors in the NTSblocked bradycardia of chemoreflex in awake rats
| Autor: | Anne Nosjean, João Carlos Callera, Benedito H. Machado, Leni G.H. Bonagamba, Raul Laguzzi |
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| Přispěvatelé: | Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto, SP, Brazil, Neuropsychopharmacologie moléculaire, cellulaire et fonctionnelle, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de la Santé et de la Recherche Médicale (INSERM) |
| Rok vydání: | 1999 |
| Předmět: |
Male
Baclofen Physiology [SDV.NEU.NB]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Neurobiology Peripheral chemoreceptors MESH: Microinjections chemistry.chemical_compound 0302 clinical medicine MESH: Animals MESH: Receptors GABA-B MESH: Receptors GABA-A 0303 health sciences MESH: Solitary Nucleus [SDV.NEU.PC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Psychology and behavior Muscimol Chemistry GABAA receptor [SDV.NEU.SC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences Chemoreceptor Cells MESH: Baclofen Cardiology and Cardiovascular Medicine circulatory and respiratory physiology medicine.drug Agonist medicine.medical_specialty MESH: Chemoreceptor Cells Microinjections MESH: Rats MESH: Reflex medicine.drug_class MESH: Cardiovascular Physiological Phenomena GABAB receptor MESH: Bradycardia Cardiovascular Physiological Phenomena 03 medical and health sciences MESH: GABA Agonists Physiology (medical) Internal medicine Reflex Bradycardia Solitary Nucleus medicine Animals Rats Wistar GABA Agonists Microinjection 030304 developmental biology MESH: Rats Wistar Bicuculline Receptors GABA-A MESH: Male Rats Endocrinology Receptors GABA-B nervous system 030217 neurology & neurosurgery MESH: Muscimol |
| Zdroj: | AJP-Heart and Circulatory Physiology AJP-Heart and Circulatory Physiology, 1999, 276 (6), pp.H1902-H1910. ⟨10.1152/ajpheart.1999.276.6.H1902⟩ AJP-Heart and Circulatory Physiology, American Physiological Society, 1999, 276 (6), pp.H1902-H1910. ⟨10.1152/ajpheart.1999.276.6.H1902⟩ |
| ISSN: | 1522-1539 0363-6135 |
| Popis: | In the present study we analyzed effects of bilateral microinjections of muscimol (a GABAA agonist) and baclofen (a GABAB agonist) into the nucleus tractus solitarius (NTS) on bradycardic and pressor responses to chemoreflex activation (potassium cyanide, 40 μg/rat iv) in awake rats. Bilateral microinjections of muscimol (25 and 50 pmol/50 nl) into the NTS increased baseline mean arterial pressure (MAP): 119 ± 8 vs. 107 ± 2 mmHg ( n = 6) and 121 ± 8 vs. 103 ± 3 mmHg ( n= 6), respectively. Muscimol at 25 pmol/50 nl reduced the bradycardic response to chemoreflex activation 5 min after microinjection; with 50 pmol/50 nl the bradycardic response to chemoreflex activation was reduced 5, 15, 30, and 60 min after microinjection. Neither muscimol dose produced an effect on the pressor response of the chemoreflex. Effects of muscimol (50 pmol/50 nl) on basal MAP and on the bradycardic response of the chemoreflex were prevented by prior microinjection of bicuculline (a GABAA antagonist, 40 pmol/50 nl) into the NTS. Bilateral microinjections of baclofen (12.5 and 25 pmol/50 nl) into the NTS produced an increase in baseline MAP [137 ± 9 vs. 108 ± 4 ( n= 7) and 145 ± 5 vs. 105 ± 2 mmHg ( n = 7), respectively], no changes in basal heart rate, and no effects on the bradycardic response; 25 pmol/50 nl only attenuated the pressor response to chemoreflex activation. The data show that activation of GABAA receptors in the NTS produces a significant reduction in the bradycardic response, whereas activation of GABAB receptors produces a significant reduction in the pressor response of the chemoreflex. We conclude that 1) GABAA but not GABAB plays an inhibitory role in neurons of the lateral commissural NTS involved in the parasympathetic component of the chemoreflex and 2) attenuation of the pressor response of the chemoreflex by activation of GABAB receptors may be due to inhibition of sympathoexcitatory neurons in the NTS or may be secondary to the large increase in baseline MAP produced by baclofen. |
| Databáze: | OpenAIRE |
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