Effects of asymmetric vertebral blood flow upon the vestibulo-ocular reflex of the rabbit.

Per-rotational nystagmus was recorded in rabbits with unilaterally narrowed vertebral arteries or following unilateral cervical sympathectomies. Asymmetry of per-rotational nystagmus could not be observed when the animal's systemic arterial blood pressure was within the normal range (about 90-120 mm Hg). However, directional preponderance of nystagmus occurred when blood pressure either increased or decreased beyond this level. The reason for the occurrence of directional preponderance can be interpreted as a failure of autoregulation of cerebral and/or inner ear blood flow.