Neurotrophins decrease degeneration of out hair cells of the guinea pig after noise trauma

doi:10.3969/j.issn.1672-2922.2003.04.002

Abstract：Objective To investigate whether glial cell line - derived neurotrophic factor (GDNF) combined with neurotrophin- 3 (NT- 3) provides the synergetic protection on hair cells (HC) from acoustic trauma. Methods Guinea pigs were ex-posed to a 4 kHz narrow band noise at 115 dB SPL for 4 hrs. The left cochlea of the animals was infused with aaificial perilymph (AP) containing (the test group) or without containing (the control group) a mixture of GDNF ( 100 ng/ml) and NT- 3(2.5μg/ml) via a mini - osmotic pump connected to the scala tympani. The infusion began at 4 days before the noise exposure and continued for 10 days after the noise exposure. Hearing function was assessed by measuring the thresholds of auditory brainstem responses (ABRs) elicited by clicks, before and 3 days after the osmotic pump implantation, and repeated 10 days after the noise exposure ( 14 days after the pump implantation). The numbers of damaged OHCs were quantitatively assessed by staining with rhodamine - phalloidin for F- actin in the cuticular plates and with Hoechst 33342 for HC nuclei. Results There was a statistically significant increase in the number of survived out hair cell (OHC) (p ＜ 0. 001, p ＜ 0.01 ) and a decrease in ABR threshold shifts (p ＜ 0.05, p ＜ 0.01 ) in both treated (left) and untreated ( right ) ears of animals received GDNF and NT- 3. Conclusion These findings indicate that GDNF combined with NT- 3 can effectively protects OHCs from noise - induced damage.