Effects of L-glutamine, glutaminase and glutamine synthetase on CAP threshold of cochlear nerve of guinea pig.
Negative direct current (-DC 300 microA) stimulation was applied to the round window of the guinea pig cochlea to exhaust the pre-synaptic intracellular reserves of the transmitter in hair cells, and then the scala tympani was perfused respectively with L-glutamine, glutamine synthetase and glutaminase. Experimental results showed that the negative DC electrical stimulation applied to the round window elevated the CAP threshold of the cochlear nerve in the basal turn of the cochlea, which recovered over a period of approximately 17-39 min. The perfusion of L-glutamine apparently elevated the CAP threshold. The recovery of the CAP threshold following electrical stimulation, however, was accelerated by the perfusion of 10 mmol/L L-glutamine. The time for recovery only took about 5-6 min. The perfusion of enzyme glutamine synthetase elevated the CAP threshold by 50 dB, while glutaminase had little effect. These results suggest that the effect of L-glutamine on the CAP threshold in the cochlea of the guinea pig appears to be that of a potent depolarizing agent which accelerates the recovery of the CAP threshold during the depletion of the transmitter, and L-glutamine may be the candidate for the afferent excitatory transmitter.
Department of Biology, University of Science and Technology of China, Hefei.
Y W
YW
Sun
D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects; D003051:Cochlea / Q000294:innervation / Q000502:physiology*; D003055:Cochlear Microphonic Potentials / Q000187:drug effects*; D004558:Electric Stimulation; D005974:Glutamate-Ammonia Ligase / Q000494:pharmacology*; D005972:Glutaminase / Q000494:pharmacology*; D005973:Glutamine / Q000494:pharmacology*; D006168:Guinea Pigs; D012405:Round Window, Ear / Q000502:physiology
D005973:Glutamine; D005972:Glutaminase; D005974:Glutamate-Ammonia Ligase