Abstract
Rats bred (generation 23) for low aerobic capacity running (LCR) and high aerobic capacity running (HCR) were studied. Body mass was significantly (P<0.001) greater in age‐matched male LCR (658 ± 35 g) than HCR (442 ± 43 g) rats. Telemetric recording of baseline ABP and HR in conscious rats revealed no statistical differences between stains. To test for differences in the contribution of sympathetic nerve activity (SNA) in the maintenance of ABP, ganglionic transmission was blocked in conscious rats with hexamethonium (20 mg/kg, iv). Within 5–10 minutes, mean ABP (MAP) fell to a similar level in LCR (n=4) and HCR (n=5) rats. Next, rats were exposed to intermittent hypoxia (IH; 3 min 21% O2 ‐ 3 min 10% O2, 8am–4pm) for 7 days to mimic the bouts of hypoxemia that occur in humans with sleep apnea. IH increased MAP from 101 ± 1 to 106 ± 1 mmHg in LCR rats (n=5) and from 104 ± 1 to 108 ± 1 mmHg in HCR rats (n=4). These findings indicated that resting ABP and its maintenance by ongoing SNA do not differ as a function of aerobic running capacity, in spite of clear differences in body mass between LCR and HCR rats. Similarly, differences in aerobic running capacity and body mass are not associated with different hypertensive responses to IH exposure. Support: HL088052, HL076312 (GMT), and RR 17718 (SLB and LGK).
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