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Muscimol into the lateral parabrachial nucleus induces sympathetic‐dependent pressor responses
Author(s) -
de Oliveira Lisandra Brandino,
De Luca Laurival Antonio,
Colombari Eduardo,
Menani José Vanderlei
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a772
Subject(s) - lateral parabrachial nucleus , muscimol , chemistry , medicine , prazosin , endocrinology , blood pressure , parabrachial nucleus , mean arterial pressure , antagonist , gabaa receptor , heart rate , receptor , hypothalamus
Previous studies have shown the importance of the lateral parabrachial nucleus (LPBN) on the control of fluid‐electrolyte balance and cardiovascular regulation. Blockade of LPBN serotonergic receptors increases arterial pressure and sodium intake induced by different stimuli. The activation of GABAA receptors by bilateral injections of muscimol into the LPBN strongly stimulates 1.8% NaCl intake in satiated and normovolemic rats. In the present study we investigated the effects of bilateral injections of muscimol into the LPBN alone or combined with intravenous injection of prazosin (α 1 adrenergic receptor antagonist) on mean arterial pressure (MAP) and heart rate (HR) in unanesthetized normotensive rats. Male Holtzman rats (baseline MAP: 115±2 mmHg; baseline HR: 368±15 bpm; n=5–7) with bilateral stainless steel guide‐cannulas implanted into the LPBN were used. Muscimol (0.5 nmol/0.2 μl) injected bilaterally into LPBN increased MAP (18±3 vs. sal. 3±2 mmHg) for at least 2 h, with no changes on HR (8±10 vs. sal. −21±17 bpm). Intravenous administration of prazosin (1 mg/kg of body weight) reduced MAP (−22±2 mmHg), increased HR (102±14 bpm) and abolished the pressor response to muscimol into the LPBN (−2±2 mmHg). The results suggest that muscimol into the LPBN induces pressor responses increasing sympathetic activity. Research supported by: FAPESP, CAPES, CNPq.