Role of the rostral ventrolateral medulla in the pressor response to stimulation of the nucleus raphe obscurus.
1. Electrical stimulation of the nucleus raphe obscurus (NRO) in urethane-anesthetized rats increases arterial blood pressure (BP) between 20 and 95 mmHg (mean, 61.14 +/- 6.57; N = 30). 2. Unilateral electrolytic destruction of the rostral ventrolateral medulla (RVLM) did not reduce BP or heart rate (HR) but significantly reduced the pressor response to NRO stimulation (control, delta 76.0 +/- 5.4 mmHg; after lesion, delta 26.0 +/- 13.9 mmHg; P < 0.01, N = 5). 3. Bilateral destruction of the RVLM reduced basal BP (control, 104.1 +/- 11.4 mmHg; after lesion, 58.0 +/- 5.7 mmHg; P < 0.01) and the pressor response to NRO stimulation (control, delta 71.6 +/- 7.3; after lesion, delta 12.5 +/- 3.8 mmHg; P < 0.01, N = 6). 4. When topically applied to or microinjected into the RVLM, pentobarbital sodium (200 nl/1 microliters, 10 nmol) decreased BP, HR and the pressor response to NRO stimulation (control, delta 56.2 +/- 6.7 mmHg; after pentobarbital, delta 11.2 +/- 3.1 mmHg; P < 0.01, N = 13). Similar effects were obtained when glycine (200 nl, 50 nmol) was microinjected into RVLM (control, delta 40.5 +/- 5.9 mmHg; after glycine, delta 18.1 +/- 4.9 mmHg; P < 0.01, N = 6). 5. We conclude that RVLM is essential for the pressor response to NRO stimulation.
Campos Júnior
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Departamento de Fisiologia, Escola Paulista de Medicina, São Paulo, Brasil.
Futuro-Neto
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Guertzenstein
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PG
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D004558:Electric Stimulation; D005998:Glycine / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D010424:Pentobarbital / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D010424:Pentobarbital; D005998:Glycine