Betahistine reduces the resting firing rate of vestibular receptors in thefrog

Although betahistine is widely used in the treatment of vertigo, it remains unclear whether it directly affects the vestibular system at the periphera l level. The effects of betahistine were therefore assessed in an isolated preparation of frog semicircular canal. Betahistine was administered either in the endolymphatic or the perilymphatic fluid and the ampullar receptor potential and mass nerve discharge were recorded at rest and during mechani cal stimulation. Endolymphatic administration was without effect. In contra st, perilymphatic administration resulted in a marked reduction in ampullar receptor resting discharge, although the mechanically evoked responses wer e only slightly affected. As vertigo is generally caused by sudden and unco ntrolled changes in the resting discharge of vestibular receptors, the abil ity of betahistine to reduce the resting firing rate of vestibular receptor s is thought to contribute to its anti-vertigo actions.