DENSE INNERVATION OF DEITERS AND HENSENS CELLS PERSISTS AFTER CHRONICDEEFFERENTATION OF GUINEA-PIG COCHLEAS

Innervation of Deiters' and Hensen's cells has been described in the o rgan of Corti of several mammalian species and has been suggested to a rise from the olivocochlear (OC) efferent system (Wright and Preston [ 1976] Acta Otolaryngol. 82:41-47). In the present study, antineurofila ment immunostaining was used to reveal these outer supporting cell fib ers (OSCFs) in the normal guinea pig. In control ears, OSCFs were abse nt in the basal half of the cochlea but increased in number steadily t oward the apex, peaking at values of over 1,200 fibers/mm. These value s indicate a far more profuse innervation of supporting cells than has been described previously, suggesting that most OSCFs were not staine d in previous immunohistochemical studies. Chronic cochlear deefferent ation was used to test whether OSCFs are part of the OC system. The OC bundle was transected unilaterally, and the animals were allowed to s urvive for 4-8 weeks. Completeness of deefferentation was assessed by using acetylcholinesterase staining of the brainstem and measurement o f the density of OC fascicles in the cochlea. By using these metrics, unilateral deefferentation was nearly complete in three animals. In su ccessfully deefferented cases, the OSCF innervation density was not st atistically different from control values. We conclude that the vast m ajority of OSCFs are not of OC origin. We speculate that they may be b ranches of type II afferent fibers to outer hair cells and that a smal ler population of OSCFs with different morphology and immunoreactivity may arise from the OC system. (C) 1998 Wiley-Liss, Inc.