Cardiovascular responses to some stressors in conscious rats.

The effects of several stressors on arterial blood pressure (BP), heart rate (HR), renal sympathetic nerve activity (RSNA) and renal blood flow (RBF) in conscious male rats were investigated. When conscious rats were exposed to smoke, the BP increased with marked decreases in HR and RBF, RSNA increased several times above the control level. During muscarinic blockade, smoke exposure reversed the HR response to an increase without any change in the RSNA. The results indicate that smoke exposure activates both the sympathetic and parasympathetic nervous systems. Whole body vibrations evoked increases in BP, HR and RSNA at frequencies less than 16 Hz. Higher frequency vibrations seemed to evoke no cardiovascular responses. It is suggested that cardiovascular responses to whole body vibration involve primarily the sympathetic nervous system.