Carotid-Sinus Baroreflex Modulation of Core and Skin Temperatures in Rats: An Open-Loop Approach

The neural mechanisms of the thermoregulatory control of core and skin temperatures in response to heat and cold stresses have been well clarified. However, it has been unclear whether baroreceptor reflexes are involved in the control of core and skin temperatures. To investigate how the arterial baroreceptor reflex modulates the body temperatures, we examined the effect of pressure changes of carotid sinus baroreceptors on core and skin temperatures in halothane-anesthetized rats. To open the baroreflex loop and control arterial baroreceptor pressure (BRP), we cut vagal and aortic depressor nerves and isolated carotid sinuses. We sequentially altered BRP in 20-mmHg increments from 60 to 180 mmHg and then in 20-mmHg decrements from 180 to 60 mmHg while measuring systemic arterial pressure (SAP), heart rate (HR), and core blood temperature (T_core) at the aortic arch and skin temperature (T _skin) at the tail. In response to the incremental change in BRP by 120 mmHg, SAP, HR, and T_core fell by 90.3±51 mmHg, 60.3±10.5 beats min^-1, and 0.18± 0.01°C, respectively. T_skin rose by 0.84±0.10°C. The maximum rate of change per unit BRP change was -2.1±0.2 for SAP, -1.5±0.4 beats min^-1 mmHg^-1 for HR, -0.003±0.001°C mmHg^-1 for T_core, and 0.011±0.002°C mmHg ^-1 for T_skin. After the administration of hexamethonium or bretylium, these baroreflexogenic responses were completely abolished. We concluded that T_core and T_skin are modulated by the arterial baroreceptor reflex.