Effects of Immobilization Stress on Regional Cerebral Blood Flow in the Conscious Rat

Abstract

Immobilization stress of conscious, normotensive, freely breathing 10-month-old Wistar-Kyoto rats produced an overall decline in regional cerebral blood flow (rCBF), as measured with [14C]iodoantipyrine, except at the frontal lobe. In 14 brain regions, rCBF fell by an average of 14.3% after 5 min of immobilization and by 11.9% after 15 min. Immobilization stress also stimulated hyperventilation and thereby reduced Paco2. The slope relating rCBF to Paco2 averaged 1.5 ml 100 g−1 min−1 mm Hg−1 in 9 significantly affected regions. The findings suggest that rCBF declines during immobilization stress because of cerebrovascular constriction caused by a reduction in Paco2. Comparison of the average slope with published values indicates furthermore that were Paco2 to remain unchanged during immobilization, rCBF would increase by at most 20%.