Protection against the lethal effects of whole body vibration by the alpha-adrenergic system in rat.

To investigate the protective mechanism against the lethal effect of whole body vibration, the phentolamine (1 mg/kg) pretreated rats were exposed to whole body vibration with a frequency of 20 Hz under an acceleration of 5 G at 24 +/- 2 degrees C and 5 +/- 1 degrees C. Five of 9 rats pretreated with phentolamine died from the exposure to whole body vibration within one hour at 24 +/- 2 degrees C. In these rats, marked infrapleural hemorrhage, dilatation of alveolar capillary vessels, and intraalveolar hemorrhage and edema were observed. However, all of the 10 rats pretreated with saline survived through the one hour exposure to the same vibration, and showed only slight histological changes in the lung. On the other hand, no rats pretreated with saline or phentolamine died from the exposure to whole body vibration within one hour at 5 +/- 1 degrees C. These results suggest that the alpha-adrenergic system and cold have a role of protection against the lethal effects of whole body vibration.