This study was performed to determine whether electrical stimulation of the autonomic centers, that is, the medial nuclei of the hypothalamus in the diencephalon causes asymmetric per-rotational nystagmus (PRN) in healthy or sympathectomized rabbits. The superior cervical ganglion was removed on one or both sides. Asymmetric PRN occurred very rarely in normal or bilaterally sympathoectomized animals, while directional preponderance (DP) appeared in more than half of the recordings in unilaterally sympathectomized animals. Although the rise in blood pressure (BP) during the intravenous influsion of norepinephrine in unilaterally sympathectomized animals also caused significant DP (previous paper), it was less than the degree of DP appearing with the same increment of BP caused by hypothalamic stimulation. Three of 5 animals with asymmetric PRN caused by stimulation showed side differences of cerebellar oxygen tension.
These findings show that asymmetric PRN following hypothalamic stimulation can be explained by a neural action on the vestibular neurons from the hypothalamus via the brainstem reticular formation or the cerebellum in addition to the asymmetric vertebral blood flow induced by symathetic vasoconstriction. We propose that this experimental model shows how psychogenic vertigo and/or dizziness can originate from distrubances of the central autonomic nervous system.