Spontaneous activity of cochlear primary afferents in post-hatch birds has been widely studied. Primary afferent spontaneous activity in avian embryos has not been described. Spontaneous activity from the two age groups was compared to determine developmental changes. Analysing the TH-sensitive period of the inner ear in more detail, we learned that the presence of TH between P3 and P12 is sufficient for normal auditory function including the developmental improvement of the threshold shift. We shall present a survey of our research on spontaneous recovery from and protrection against hearing damage due to cisplatin administration in the guinea pig.
Circumstantial evidence suggests that the lesions occur late in the administration period.
After sixteen weeks the compound action potential amplitude tends to decrease again while we noticed vacuolation in the spiral ganglion. Chronical electrophysiological studies confirmed spontaneous recovery within animals after the cisplatin administration. The protective effect appears to be insensitive to the cisplatin dose while keeping the dose of the neuropeptides constant. This result suggests that animal-dependent systemic responses to the neuropeptides might be involved in their protective action. Also, the occurrence of hearing loss late in the administration period when no concomitant peptide is given suggests that concomitant administration of the neuropeptides may delay the accumulation of hearing loss.