Postnatal cochlear function development in normal dogs and deaf Dalmatians

Pigmentation-associated congenital deafness occurs in humans and other species, including dogs (especially Dalmatians). The deafness generally results from degeneration of the stria vascularis after an otherwise normal period of development; time of occurrence is unknown in humans but is early postnatal in several animal species. Noninvasive perinatal studies of audition in dogs are not possible until 2–3 weeks of age, when the ear canals open. Methods developed to follow the postnatal development of peripheral auditory function in dogs and preliminary findings in normal pups and deaf Dalmatians are reported here. Surgery was performed 24–48 h after birth to implant recording electrodes and tubing for auditory stimulation in the sealed ear canal near the tympanum. Pups stayed with mothers except for recordings. Daily recordings (150–3000 Hz, 10 ms) were collected between the implanted electrode and vertex in response to click stimuli (100 μs, 11.4/s, 135 dB SPL [machine setting]) applied through the implanted tubing. The normal postnatal pattern of response development is presented. Deafness in Dalmatians developed by 3 weeks following normal initial development. [Work supported by NIH/NIDCD.]