Autoregulation of spinal cord blood flow.

The response of SCBF to changes in pACO2 was tested in Rhesus monkeys under normotensive conditions. A sigmoid shaped response was demonstrated. At a pACO2 of 10 to 50 mm. Hg, SCBF remained constant and in the normal range. As the pACO2 was raised from 50 to 90 mm. Hg, SCBF increased. Further increases in the pACO2 above 90 mm. Hg failed to effect further changes in SCBF. We conclude from these data that SCBF is somewhat less responsive than CBF to changes in pACO2. Next, the effect of changes in MAP on SCBF was studied under normocapnic conditions. SCBF remained constant and in the normal range with an MAP of 50 to 135 mm. Hg. Above 135 mm. Hg, SCBF rose with further increases in MAP. With decreases in MAP below 50 mm. Hg, SCBF fell passively. It is our conclusion that autoregulation exists in the lateral white matter of the spinal cord and follows a pattern similar to that suggested for the cerebrum.