The relevance of peripheral baroreceptors and chemoreceptors to regulation of cerebral blood flow in the cat.

The contribution of neural vasomotor reflexes to the control of cerebral blood flow (CBF) was investigated in 30 cats lightly anesthetized with pentobarbital. CBF was measured both by kinetic analysis and by the intial slope technique of the washout curve of a bolus of 133Xe. Autoregulation (10 cats) and responsiveness to alteration in arterial PCO2 (PaCO2) (10 cats) and arterial PO2 (Pao2) (five cats) were assessed both before and after bilateral intracranial division of the 9th and 10th nerves. In an additional group (five cats), related changes in CBF to alteration of PaCO2 were recorded before and after unilateral section of the 7th and 8th nerves. Autoregulation was preserve after division of the 9th and 10th nerves and there was no significant change in the PaCO2 response curves. Section of the 7th and 8th cranial nerves did not produce conclusive results in the small number of cats studied. A conclusion that the facial nerves are not dominant in responses to hypercapnia seems justified, but a modulating role for these nerves is possible. These studies do not exclude a physiological role for these nerves in the autoregulation of CBF, but do indicate that the cerebral vascular bed apparently is capable of functioning normally after their division.