The effect of bicuculline application on auditory response properties of inferior collicular neurons of mice with or without monaural middle ear destruction in early age.
Previous studies have demonstrated that abnormal auditory stimulation during early postnatal development can be manifested through physiological changes that occur in the inferior colliculus (IC) of mammals. To determine the contribution of the GABAergic transmitter systems to the development of response properties of IC neurons, we examined the effect of application of bicuculline (which is an antagonist for the GABA(A) receptors) on response properties of IC neurons of the laboratory mice, Mus musculus, with or without early monaural middle ear destruction. Monaural middle ear destruction was performed at 12-14 days after birth. At adulthood, the auditory response properties of IC neurons were examined in both experimental conditions. All IC neurons determined before and during bicuculline application can be described as (1) phasic responders which discharged 1-2 impulses; (2) phasic bursters which discharged 3-7 impulse; and (3) tonic responders which discharged impulses throughout the duration of presented sound pulses. Early monaural middle ear destruction only affected the percent distribution but not the type of discharge pattern, rate-intensity function and frequency tuning curve of IC neurons in the control and experimental mice. Neurons in the contralateral IC of experimental mice typically had longer latencies, higher minimum thresholds, broader frequency tuning curves and smaller dynamic ranges than neurons in the ipsilateral IC and in control mice. Bicuculline application produced differential effects in decreasing the latencies and minimum thresholds as well as broadening frequency tuning curves and dynamic ranges of IC neurons in these two groups of mice. All these data suggest that early monaural middle ear destruction did not affect the shaping of auditory response properties of IC neurons by GABAergic transmitter system.
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National Center for Physical Acoustics, University of Mississippi, 38677, USA.
Jen
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D000367:Age Factors; D000818:Animals; D001309:Auditory Threshold / Q000502:physiology*; D001640:Bicuculline / Q000494:pharmacology*; D004432:Ear, Middle / Q000293:injuries* / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology; D005260:Female; D018756:GABA Antagonists / Q000494:pharmacology*; D007245:Inferior Colliculi / Q000166:cytology* / Q000502:physiology; D008297:Male; D051379:Mice; D023421:Models, Animal; D009474:Neurons / Q000187:drug effects*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology
D018756:GABA Antagonists; D001640:Bicuculline