Intraotic Administration of Gentamicin: A New Method to Study Ototoxicity in the Crista Ampullaris of the Bullfrog

Abstract

A new method of local gentamicin administration was tested in the bullfrog inner ear to achieve ototoxic-induced hair cell destruction. Gelfoam pledgets soaked with known amounts of gentamicin were inserted into the perilymphatic cisterna of the bullfrog through a ventral surgical approach. A dose of 1.20 mg gentamicin, consistent with a perilymphatic concentration of 65 microg/ml, resulted in the desired ototoxic-induced hair cell damage, that is, complete hair cell destruction with minimal disruption of other components of the sensory epithelium. This study demonstrates that this is a useful and simple method to investigate the process of vestibular ototoxicity and hair cell regeneration, including aspects of hair cell destruction and repair.

Gentamicin ototoxicity in the saccule of the lizard Podarcis Sicula induces hair cell recovery and regeneration

“…Twenty-eight days after Gm treatment, the morphology of the saccule appeared normal, with no signs of ototoxic damage. This finding is consistent with Carranza et al (1997), who demonstrated recovery of the sensory epithelium in the posterior crista of the bullfrog 4 weeks post-Gm treatment. In contrast, Baird et al (1993) found regenerating hair cells in the saccular and utricular maculae as early as 4-48 h after aminoglycoside treatment.…”

Hair Cell Recovery in the Chinchilla Crista Ampullaris after Gentamicin Treatment: A Quantitative Approach

“…The methods for the preparation of gentamicin pellets and their administration in the perilymphatic space have been described previously. 4,6,[17][18][19] Four groups of three chinchillas each were treated with 50 µg gentamicin, and subsequently euthanized 7, 14, 28, and 56 days after treatment. The horizontal crista of each treated ear was histologically processed for light and TEM examination.…”

Streptomycin ototoxicity and hair cell regeneration in the adult pigeon utricle

“…Localized intraotic administration of aminoglycosides has been previously reported in studies involving amphibian species 6–8 . Omura et al 8 compared intralabyrinthine, intramuscular, and intraperitoneal injections of gentamicin into the bullfrog and found that the intralabyrinthine administration route is not only the most destructive but also the most efficient method.…”

“…However, even with intraotic injections of gentamicin up to lethal dosages, these investigators did not see destruction of extrastriolar hair cells. Recently, Carranza et al 7 inserted gentamicin‐soaked gelfoam pledgets directly into the perilymphatic cisterna of the bullfrog, and demonstrated dose‐dependent ampullary hair cell destruction, although they did not comment on the utricular neuroepithelia.…”

“…Subsequently, research into the mechanisms of hair cell regeneration in the auditory epithelium has been quite active. Using administration of gentamicin or streptomycin to destroy hair cells, investigators have documented hair cell regeneration in the vestibular neuroepithelium of birds and amphibians 2,6–11 . The emphasis has been on ampullary hair cell regeneration.…”