Toxic effects of gentamicin on the basilar papilla in the lizard Calotes versicolor. A surface study

Gentamicin in a dose of 100 mg and in some cases 150 mg per kg bodyweight and day was given intraperitoneally to healthy lizards, belonging to the species Calotes Versicolor. The animals were injected for 7, 14 and 21 days. After completed injections the animals were sacrificed and their hearing organ, the basilar papilla, was processed for scanning electron microscopy. Animals treated for 7 days did not show any significant surface damage in the basilar papilla. When gentamicin was administered for 14 days the normal appearance of the surface structure was lost. The ventral (apical) type A cells were relatively intact while the type B cell-population in the dorsal (basal) part of the organ showed sensory hair fusions and cytoplasmic herniations. Lizards treated for 21 days showed a severely damaged basilar papilla. The ventral (apical) type A cells still only were moderately damaged with some hair fusions and cytoplasmic herniations while the dorsal (basal) type B cells were more or less destroyed. Only occasional cells were left and some of these were severely damaged. The surface of the dorsal (basal) part of the organ instead was covered by supporting cells thus forming a sort of scar tissue.