Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats

Sadamoto, Tomoko, and Kanji Matsukawa. Cardiovascular responses during spontaneous overground locomotion in freely moving decerebrate cats. J. Appl. Physiol.83(5): 1454–1460, 1997.—To examine whether the cerebrum is essential for producing the rapid cardiovascular adjustment at the beginning of overground locomotion, we examined heart rate (HR), mean arterial blood pressure (MAP), and integrated electromyogram (iEMG) of the forelimb triceps brachialis muscle in freely moving decerebrate cats during locomotion. Two to four days after decerebration surgery performed at the level of the precollicular-premammillary body, the animals spontaneously produced coordinated overground locomotion, supporting body weight. HR began to increase immediately before the onset of iEMG, and MAP began to rise almost simultaneously with the iEMG onset. Their increases in HR and MAP (24 ± 3 beats/min and 22 ± 4 mmHg) were sustained during locomotion. Sinoaortic denervation (SAD) did not affect the abrupt changes in HR and MAP at the beginning of locomotion (0–4 s from the onset of iEMG), whereas SAD had a contrasting effect during the subsequent period, a decrease in the HR response (9 ± 1 beats/min) and an increase in the MAP response (30 ± 3 mmHg). These results suggest that the cerebrum and the rostral part of the diencephalon are not essential for producing the rapid cardiovascular adjustment at the beginning of spontaneous overground locomotion. The arterial baroreflex does not contribute to this rapid adjustment but plays an important role in regulating the cardiovascular responses during the later period of spontaneous locomotion.

Children in Sauna: Cardiovascular Adjustment

Children's circulatory adjustment to a 10-minute heat stress in a climatic chamber was studied in 61 children and 20 adolescents and young adults. The thermal conditions corresponded to those of an ordinary Finnish sauna bath. In all subjects the rectal temperature and heart rate increased during the heat exposure (P < .001). Systolic and diastolic blood pressures remained unchanged in sauna, but the systolic and especially the diastolic blood pressure decreased (P < .001) in children less than 10 years of age immediately after the heat exposure; two vasovagal collapses developed. Cardiac output increased in all but the less than 5-year-old children (P < .001). This was due to a significant decrease in stroke volume (32.9%) (P < .001) in children less than 5 years old. Stroke volume declined slightly even in the older subjects. These changes indicate that the Finnish sauna bath puts great demands on a child's circulatory regulation. To avoid possible cardiovascular side effects, particularly small children should be supervised carefully during sauna bathing.