Vestibular function and vasopressin.

Abstract

To investigate the relation between the vestibular system and vasopressin (AVP). We examined the effects of electrical and caloric vestibular stimulation on plasma AVP levels in anesthetized rats. Plasma AVP levels of patients with intractable Ménière's disease who were subjected to endolymphatic drainage and steroid instillation surgery (EDSS) or intratympanic gentamicin (GM) injection were measured before and after these interventions. Electrical vestibular stimulation increased plasma AVP levels in a current intensity-dependent manner. Plasma AVP levels were also increased by caloric stimulation with cold water. Plasma AVP levels decreased rapidly after EDSS, and were maintained at a low level even 6-12 months following EDSS or intratympanic GM injection. Vestibular activation or inhibition-induced imbalance of intervestibular activities increased plasma AVP levels in rats. Therefore, vestibular disorder would seem to increase plasma AVP and thus worsen endolymphatic hydrops. EDSS rapidly decreased plasma AVP and would seem to reduce hydrops. Inhibition of vertigo spells by EDSS or intratympanic GM injection would reduce a possible stress response, resulting in a decrease in plasma AVP levels a long time after the treatments. This resultant decrease in AVP would beneficially inhibit the formation and/or maintenance of hydrops and thus prevent vertigo spells.