Control of baboon limb blood flow and heart rate, role of skin vs. core temperature

To discover the relative importance of body core temperature versus body skin temperature in raising limb blood flow and heart rate, the authors exposed seven unanesthetized, chaired baboons (Papio anubis) to a variety of heating protocols. First, the baboons were exposed to a 40-45°C environment for 0.75-1.5 h. Arterial or right atrial blood temperature (T(bl)), skin temperature (T(sk)), mean right iliac blood flow (MRIF), and heart rate (HR) all increased gradually during heating. On the average, HR increased from 106 to 160 beats/min and MRIF rose to 286% of control level. To separate influences of T(bl) and T(sk) on cardiovascular changes, the authors manipulated T(bl) and T(sk) independently via a heart exchanger incorporated into a chronic femoral arteriovenous shunt. In most baboons, the MRIF and HR response to a hot environment could be essentially duplicated by elevation of T(bl) with T(sk) held neutral, while elevation of T(sk) with T(bl) held neutral had little effect. One baboon exhibited significant response to T(sk) elevation with T(bl) held neutral, although subsequent manipulation of T(bl) overrode this response. The authors conclude that the normal response to heating in baboons is mainly attributable to drives from internal temperature sensitive mechanisms. Elevated T(sk) shows large effects only in exceptional cases.