The Human Neuroprotective Placental Protein Composition Suppressing Tinnitus and Restoring Auditory Brainstem Response in a Rodent Model of Sodium Salicylate-Induced Ototoxicity

Abstract

The effect of neuroprotective placental protein composition (NPPC) on the suppression of tinnitus and the restoration of the auditory brainstem response (ABR) characteristics was explored in tinnitus-induced rats. The animals were placed into two groups: (1) the study group, rats received sodium salicylate (SS) at the dose of 200 mg/kg twice a day, for two weeks, and then 0.4 mg of the NPPC per day, between the 14th and 28th days, (2) the placebo group, rats received saline for two weeks, and then the NPPC alone between the 14th and 28th days. The gap pre-pulse inhibition of the acoustic startle (GPIAS), the pre-pulse inhibition (PPI), and the ABR assessments were performed on animals in both groups, three times (baseline, day 14, and 28). The GPIAS value declined after 14 consecutive days of the SS injection, while NPPC treatment augmented the GPIAS score in the study group on the 28th day. The PPI outcomes revealed no significant changes, indicating the preservation of hearing after the SS and NPPC administrations. Moreover, some changes in ABR characteristics were observed following SS injection, including (1) higher ABR thresholds, (2) lowered waves I and II amplitudes at the frequencies of 6, 12, and 24 kHz and wave III at the 12 kHz, (3) elevated amplitude ratios, and (4) growth in brain stem transmission time (BTT). All the mentioned variables subsequently returned to their normal values upon applying the NPPC. The NPPC use could exert positive therapeutic effects on the tinnitus-induced rats, and improve their ABR characteristics.

Note:
Funding declaration: This study was financially supported by the Iran National Science Foundation (INSF, Synergy Grant Code no. insf-98020383-1400/03/23), and ENT and Head & Neck Research Center, Hazrate Rasoul Akram Hospital, the Five Senses Institute, School of Medicine, Iran University of Medical Sciences, Tehran, Iran (Ethical approval no. IR.IUMS.REC.1398.233).

Conflicts of Interest: None

Ethical Approval: All the procedures were performed under the National Institutes of Health Guide for the Care and Use of Laboratory Animals (NIH Publication No. 8023, revised 1978), and then approved by the Vice-Chancellor's Ethical Committee for Medical Research, Iran University of Medical Sciences, Tehran, Iran (Ethical approval no. IR.IUMS.REC.1398.233).

Keywords: tinnitus, evoked potentials, auditory, Auditory Brain Stem Response, Placental Extract