HPLC detection of serotonin within the rat cochlea

THIS study was performed to analyse the cochlear concentrations of serotoni n (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), their sources and modi fications induced by noise exposure. Superior cervical ganglionectomy did n ot modify these concentrations. However, removal of the blood by aortic per fusion reduced significantly (about 76%) the cochlear concentration of 5-HT without affecting the 5-HIAA concentration. These results indicate that bl ood constitutes an important source of 5-HT to the cochlea, opposite to the superior cervical ganglion. Exposure to noise at 90 dB SPL did not modify the total cochlear concentrations of 5-HT and 5-HIAA, or the concentrations remaining after removal of the blood, suggesting that 5-HT could have a mo dulatory role in the cochlea distinct from that of olivocochlear neurotrans mitters. Neuroreport 9: 3699-3701 (C) 1998 Lippincott Williams & Wilkins.