Effects of acoustic overstimulation and perilymph perfusion--with Joro spider toxin on the concentrations of amino acids in the perilymph

Abstract

Glutamate (Glu) is considered one of the most probable neurotransmitter candidates in primary afferent nerves of the cochlea. In the present study, the amino acid profile in the perilymph was determined in order to investigate the effects of acoustic overstimulation and perilymph perfusion with Joro Spider Toxin (JSTX), a specific antagonist of the quisqualate sensitive Glu receptor, on the stimulus-induced release of Glu. In the first series of experiments (control group; n = 10), samples of the scala tympani perilymph (PST) were collected from albino guinea pigs at 60 and 75 min after initiating cochlear perfusion with an artificial perilymph. In the second series of experiments (acoustic overstimulation group; n = 7), the PST samples were collected before (at 60 min after the initiation of perilymph perfusion) and after (at 75 min after the initiation of perilymph perfusion) exposure to a pure tone (2000 Hz, 110 dBSPL for 15 min). In the third series of experiments (JSTX group; n = 8), the PST samples were collected as described above under condition of cochlear perfusion with an artificial perilymph containing of 3.54 x 10(-8) M and 3.54 x 10(-6) M of JSTX. The concentrations of Glu, aspartate, glycine, alanine and leucine were measured by high-performance liquid chromatography (HPLC) using phenylisothiocyanate derivatization. There was no significant effect of acoustic overstimulation or perilymph perfusion with JSTX on the levels of amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)