【Purpose】 Optimal exercise performance depends upon appropriate circulatory regulation and blood supply to active skeletal muscles. We hypothesized that the hypothalamic tuberomammillary nucleus (TMN) is the anatomical territory actively involved in the central command, which refers to a feed-forward control of hemodynamic regulation, including blood flow (BF) redistribution during exercise. To test this hypothesis, we investigated the effects of TMN stimulation on mean arterial pressure (MBP), heart rate (HR), and BF to the skeletal muscles and kidney, which constitutes an important intra-abdominal organ. Furthermore, we calculated the peripheral vascular resistance (VR).
【Method】 Microelectrodes were inserted into the TMN of urethane-anesthetized Wistar rats (n = 10), followed by microelectrical stimulation (200 µA, 50 Hz, and 30 s). We measured the MBP, HR, and muscle and renal BF in response to electrical stimulation of the TMN. We histologically identified the stimulation site after the experiment.
【Results】 We observed a significant increase in the MBP (4.67 ± 0.59 mmHg), renal VR (0.31 ± 0.06 mmHg/mL/min), and muscle BF (2.25 ± 0.88 mL/min) and a decrease in renal BF (-1.27 ± 0.31 mL/min) upon electrical stimulation of the TMN; however, no significant changes were observed in the HR (1.31 ± 1.14 beats per minute) and muscle VR (-0.36 ± 0.27 mmHg/mL/min).
【Conclusion】 This study highlights that TMN may be involved with organ-specific modulation of vasoactive sympathetic innervation. Further studies are warranted to investigate whether the TMN affects BF redistribution during exercise.
