Allografted fetal dorsal root ganglion neuronal survival in the guinea pig cochlea.

Neural grafting is a potential strategy to help restore auditory function following loss of spiral ganglion cells. As a first step towards the reconstruction of a neural pathway from the cochlea to the brainstem, we have examined the survival of fetal dorsal root ganglion (DRG) neurons allografted into the cochlea of adult guinea pigs. In some animals implantation of DRGs was combined with a local infusion of neurotrophic substances whereas in others auditory sensory receptors were chemically destroyed prior to DRG implantation by injection of the ototoxin neomycin into the middle ear. The results show that many transplanted DRG neurons attached close to the cochlear spiral ganglion neurons. The survival of the implant was significantly increased by treatment with neurotrophic factors, but not reduced by the absence of auditory sensory structures. This study shows that implanted sensory neurons can survive heterotopic grafting immediately adjacent to the eighth cranial nerve, thereby providing a basis for further studies of the anatomical and functional influence of neural grafts in the inner ear.