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Exaggerations in skeletal muscle metaboreflex activity are attenuated by increasing nitric oxide production within the brainstem of spontaneously hypertensive rats
Author(s) -
Leal Anna K,
Mitchell Jere H,
Smith Scott A
Publication year - 2009
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.23.1_supplement.608.1
Subject(s) - nitric oxide , medicine , endocrinology , brainstem , blood pressure , spontaneously hypertensive rat , capsaicin , skeletal muscle , receptor
In hypertension, evidence suggests the skeletal muscle metaboreflex (SMM) is exaggerated and contributes significantly to the heightened blood pressure (BP) response to exercise in this disease. The mechanisms underlying SMM overactivity remain unknown. Sensory information elicited by the SMM is processed within the nucleus tractus solitarius (NTS) of the brainstem. Normally, endogenously produced nitric oxide (NO) within the NTS attenuates the BP response elicited by the SMM. Therefore, we hypothesized that a decrease in the availability of NO within the NTS mediates the exaggerated SMM activity manifest in hypertension. The SMM was preferentially activated by injecting capsaicin (0.3 μg/ 100 μL) into the hindlimb arterial supply of male normotensive Wistar Kyoto (WKY; n=4) and spontaneously hypertensive (SHR; n=5) rats before and after the dialysis of the NO precursor L‐arginine (1.0 μM) into the NTS. Capsaicin injections resulted in larger increases in BP in SHR (41±9 mmHg) than WKY (21±4 mmHg). In both groups, L‐arginine dialysis attenuated the BP response. Interestingly, the magnitude of this reduction was greater in SHR (‐12±5 mmHg) than WKY (‐3±1 mmHg). Augmenting NO availability in the NTS partially corrected the exaggerated BP response to SMM activation in SHR. This finding suggests that decreases in NO within the NTS may contribute to SMM overactivity in hypertension. Supported by NIH HL‐088422