Morphological and physiological effects of long duration infusion of strychnine into the organ of Corti

Acute strychnine administration has long been used as a method to eliminate the effects of efferent activity. It has been shown that long after termin ation of chronic strychnine infusion into the cochlea, the ear becomes more susceptible to acoustic trauma suggesting that chronic strychnine infusion results in long lasting or permanent disruption of efferent function. Much research has been directed towards the functional significance of the oliv ocochlear system. However, there is little information concerning the effec t of long duration inactivation of the medial olivocochlear system in an aw ake behaving animal. This study was designed to determine the structural an d functional consequences of inactivation of the efferents by chronic infus ion of strychnine into the cochlear perilymph of guinea pigs for two weeks via an osmotic pump. Physiological evaluations showed that the strychnine i nfusion eliminated the efferent induced reduction of the cochlear whole-ner ve action potential three weeks after cessation of strychnine infusion. Con tralateral efferent function remained unaltered. Histological evaluation at the light and electron microscopic levels revealed disoriented efferent sy napses under the outer hair cells.