Experimental study of the mechanism of the decrease in endocochlear d.c. potential after administration of nitrogen...

Area of Science:

• Ototoxicity research
• Auditory physiology
• Pharmacology

Background:

• Nitrogen mustard (NM) affects the endocochlear potential (EP), a key indicator of cochlear function.
• Understanding the ototoxic mechanisms of NM derivatives is crucial for developing safer therapeutic agents.

Purpose of the Study:

• To investigate the ototoxic effects of nitrogen mustard-N-oxide hydrochloride (NMNO) on the endocochlear potential (EP).
• To elucidate the mechanism underlying NMNO-induced changes in cochlear function.

Main Methods:

• Administration of varying doses of NMNO to guinea pigs.
• Measurement of endocochlear potential (EP) and cochlear partition electrical resistance.
• Histological examination of the stria vascularis.
• Experiments involving prior kanamycin sulfate (KM) treatment to destroy the organ of Corti.

Main Results:

• A single dose of 20 mg/kg NMNO caused a transient decrease in EP magnitude, similar to NM.
• Higher NMNO doses (40-80 mg/kg) did not produce a dose-dependent reduction in EP.
• No ultrastructural changes were observed in the stria vascularis, even at high NMNO doses.
• NMNO did not reduce EP in animals with a pre-existing destroyed organ of Corti.

Conclusions:

• The reduction in EP by NMNO is not due to impaired cochlear electrical insulation or stria vascularis dysfunction.
• The organ of Corti is implicated as the primary target site for NMNO-induced EP reduction.
• Further research into the organ of Corti's role is necessary to understand NMNO ototoxicity.