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Role of A1 noradrenergic neurons in the pressor response induced by hypertonic saline (HS) infusion in unanesthetized rats
Author(s) -
Pedrino Gustavo R,
Korin Willian S,
Cravo Sergio L
Publication year - 2008
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.22.1_supplement.738.19
Subject(s) - microinjections , medicine , endocrinology , hypertonic saline , saline , medulla , lesion , chemistry , mean arterial pressure , homeostasis , anesthesia , blood pressure , microinjection , heart rate , pathology
Several findings suggest that A1 noradrenergic neurons in the caudal ventrolateral medulla (CVLM) contribute to body fluid homeostasis. The present study sought to determine the effects of lesions of these neurons on the cardiovascular responses induced by HS infusion in awake rats. All experiments were performed in Wistar rats (280–350g). Lesion of A1 neurons were performed by microinjections of anti‐DβH–saporin (6.3 ng in 60 nl; SAP‐rats, N=8) into the CVLM, whereas sham rats received microinjections of free saporin (1.3 ng in 60 nl, N=6). Two weeks later the rats were instrumented for mean arterial pressure (MAP) and heart rare (HR) recordings. In the following day, rats were submitted to iv infusion of HS (3M NaCl, 0.18 ml/100g bw, 1 min). In sham rats, HS induced a sustained (>90min) increase of MAP (38±3 mmHg, 10 min) and a reduction in HR (−42±12 bpm, 10 min). In SAP‐rats, we observed a significant reduction in the changes in the MAP (15±3 mmHg) and a decrease of HR (−50±13 bpm). Hypernatremia induced by HS was similar in sham (146±1.4 mM) and SAP‐rats (146±0.9 mM). Blood hemoglobin concentration remains unchanged after HS in sham rats (100±0.3%). However, in SAP‐rats, we observed a sustained increased on this parameter (108±2%). Extension of A1 neurons lesion was confirmed by immunocytochemistry. These results suggest that A1 neurons mediate pressor response to acute changes in circulating volume. Supported by CAPES.