Betahistine increases vestibular blood flow

Betahistine is used for treatment of several vestibular disorders. Despite the accepted use of this histamine-like substance, its mechanism of action is not well understood. The purpose of this study was to assess the possibi lity that one of the activities of betahistine is increasing blood flow in the peripheral vestibular end organs. Using a novel surgical approach, we i dentified the posterior semicircular canal ampulla of guinea pigs and place d a laser Doppler probe in position to obtain blood flow measurements from the posterior semicircular canal ampulla, Blood pressure, heart rate, and v estibular blood flow were continuously recorded, Concentration-response cur ves were obtained for betahistine (2.5, 5, 7.5, and 10 mg/kg) and control-v ehicle (0.15 mol/L NaCl) infusions, A separate group of subjects was pretre ated with the competitive selective H3 agonist, thioperimide maleate, befor e betahistine treatment. Increases in vestibular blood flow and decreases i n blood pressure were observed in response to betahistine infusions. Pretre atment with thioperamide maleate abolished these changes at low doses of be tahistine and attenuated the responses at higher doses of betahistine, Thes e results show that betahistine administration induces increases in vestibu lar blood flow. These findings support the potential use of betahistine for treatment of vestibular disorders, which may be caused by compromised circ ulation.