Lower body negative pressure in the tranquilized rat.

The application of lower body negative pressure (LBNP) to tranquilized rats was assessed as an experimental technique to evaluate the response of the cardiovascular system to hypotension. After pilot studies had demonstrated that diazepam (600 micrograms X kg-1, i.v.) had no significant influence on the pressor response to unilateral carotid occlusion in unanesthetized and unrestrained rats, subsequent rats were tranquilized. When LBNP was applied, the decline in central venous pressure was linearly related to the level of negative pressure as was the initial fall in mean arterial pressure (MAP). Pulse-interval was highly correlated with the initial fall of MAP. The results indicate that the application of LBNP in the tranquilized rat can effectively produce systemic hypotension and elicit cardiovascular reflexes similar to those reported for other animals in response to LBNP, including humans.