Figure 1

Oral administration of caffeine aggravates cisplatin-induced hearing loss. (A) A schematic of the experimental protocol that depicts the dosage and routes of administration of different drugs. Wistar rats were divided into six groups and treated with either oral caffeine (15 mg/kg), followed by trans-tympanic delivery of vehicle or R-PIA (1 μM) in both ears. This was followed by intraperitoneal administration of vehicle or cisplatin (11 mg/kg) 30 min later. Pre-treatment ABRs were measured just before the drugs were administered and post-treatment ABRs was determined 72 h following cisplatin. PO: Per os (oral); TT: Trans-tympanic; IP: Intraperitoneal. (B) ABR thresholds were recorded in Wistar rats treated with cisplatin (11 mg/kg, IP) after oral administration of caffeine (15 mg/kg) or caffeine + R-PIA (1 µM, TT). Post-treatment ABRs assessed 3 days later showed significant elevations in thresholds in cisplatin and caffeine + cisplatin groups at 8 and 16 kHz frequencies. At 32 kHz, caffeine co-administration produced hearing loss which was significantly greater than cisplatin alone. Trans-tympanic delivery of R-PIA attenuated the increase in ABR thresholds produced by caffeine + cisplatin at all the frequencies tested. Data indicate mean ± SEM of five rats. Asterisks, *p < 0.05 vs. vehicle, **p < 0.05 vs. cisplatin and ^#p < 0.05 vs. caffeine + cisplatin (one-way ANOVA).