Short-Term Functional and Morphological Changes in Guinea Pig Cochlea following Intratympanic Application of Burow's Solution

Abstract

Burow's solution, comprising aluminum sulfate and acetic acid, is an otic drug formulation applied to the tympanic cavity. We characterized the relationship between the auditory brain stem response (ABR) thresholds and the area of the capillary basement membrane anionic sites in the stria vascularis after the application of Burow's solution. We used cationic polyethylenimine (PEI) to observe changes in the capillary basement membrane anionic sites in the stria vascularis. Burow's solution was dropped directly onto the round window membrane and retained for 2 hours. The ABRs were recorded at 4, 8, and 20 kHz immediately before surgery and before decapitation. The cochlea was extirpated immediately or 2 days after the surgery and immersed in cationic PEI solution. The PEI distribution associated with the capillary basement membrane anionic sites was measured in the basal and third turns. The ABR threshold shifts at 4, 8, and 20 kHz were significantly increased immediately after the surgery, whereas those at 4 and 8 kHz, but not at 20 kHz, had recovered 2 days after the surgery. Further, the PEI distribution was significantly decreased immediately after the surgery and had recovered 2 days after the surgery. Although Burow's solution may cause an acetic low pH in the stria vascularis and a temporary ABR threshold shift at 4 and 8 kHz, the permanent ABR threshold shift at 20 kHz cannot be attributed to the acetic low pH.