Effect of acoustic overstimulation on regulation of glucocorticoid receptor mRNA in the cochlea of the guinea pig

Semi-quantitative reverse transcription polymerase chain reaction was perfo rmed to determine the distribution of mRNA levels of glucocorticoid recepto r (GR) within the guinea pig cochlea and to examine the change in their exp ression after acoustic overstimulation. Using an original PCR primer for th e guinea pig, the highest GR mRNA level was revealed in the modiolus and lo west in the medial portion including the organ of Corti. Total RNA was extr acted from the whole cochlea of the guinea pig 0, 2, 6 and 24 h after expos ure to a 2 kHz pure tone of 110, 120 or 130 dB SPL for 10 min. The level of GR mRNA significantly decreased immediately and 2 h after exposure to the sound of 120 dB SPL, and 2 and 6 h after exposure to that of 130 dB SPL. Th ese results suggest the presence of a down-regulation of GR mRNA induced by acoustic overstimulation, although the exact mechanism of this phenomenon remains unsolved. (C) 2001 Elsevier Science B.V. All rights reserved.