EFFECTS OF PROSTACYCLIN ON HEAVING RECOVERY ALTER REPETITIVE NOISE AND ON HISTOMORPHOLOGY OF THE INNER-EAR IN THE GUINEA-PIG

A probable relation between prostaglandin formation and the pathophysi ology of hearing loss led to the application of the potent vasodilator prostacyclin in the treatment of inner ear disorders. Two drugs may b e administered to humans: (1) unstable natural prostacyclin (epoproste nol) with a strong biological potency but with a high first-pass effec t, or (2) a prostacyclin analogue (taprostene) with less biological ac tivity, but a longer biological half-life and intravenous application. Therefore, the purpose of this study was to investigate potential dif ferences of both drugs in their effect on the inner ear. The therapeut ic potency of both drugs was evaluated in a recently developed animal model consisting in the recovery of hearing after a temporary threshol d shift obtained by two noise exposures at 100 dB. In addition, the ul trastructure of the stria vascularis was examined by electron microsco py after the application of the drugs. After administering epoprosteno l (12 ng/kg body weight/min) and taprostene (25 ng/kg body weight/min) histomorphological alterations in the stria vascularis did not differ from the controls. In the repetitive low-level noise model, neither d rug showed a significant difference in its effect on the recovery of t he hearing threshold. The results indicate that in the guinea pig epop rostenol has the same effect on the hearing threshold as the stable an alogue taprostene, as shown by auditory brain stem response.