Influence Of Monaural Plugging On Postnatal Development Of Auditory Spatial Response Properties Of Inferior Collicular Neurons In Bat, Myotis Chinensis And The Mechanism

Using electrophysiological method and immunohistochemical technique, we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensis and the mechanism.The results were summarized as:1.Auditor)' spatial response properties of inferior collicular neurons in bat, Myotis chinensisAuditory spatial response properties of inferior collicular(IC) neurons of bat, Myotis chinensis, were studied using electrophysiological method under free-field conditions. The results showed that the distribution of response centers of 1C neurons was concentrated and most of them located within 10??40?contralateral in azimuth, 5??25?down in elevation of the frontal auditory space. The relationship between the locations of response centers of 1C neurons and their best frequencies(BFs) appeared to be less predicatable. The number of impulses of neuron varied when the acoustic stimulus was delivered from different positions within its auditory spatial response area. The auditory spatial response area expended asymmetrically with the stimulus intensity and there was relation between the size of auditory spatial response area and neuron's BF.2.Influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular neurons in bat, Myotis chinensisUnder free-field conditions.we studied the influence of monaural plugging on postnatal development of auditory spatial response properties of inferior collicular(IC) neurons in bat, Myotis chinensis using electrophysiological method. The results showed that monaural plugging did not alter the distribution of best frequency(BF) and latency of 1C neurons, but it raised the minimum threshold(MT) of 1C neurons. The monaural plugging also appeared to modify the auditory spatial responseproperties of 1C neurons. Thus, when the earplug was removed, the response centers of 1C neurons contralateral to plugged ear were scattered over a wider area of auditor}' space than when the earplug was intact and the control bats. Furthermore, the sizes of auditory spatial response areas were bigger and the variations in MT and number of impulses to a BF sound delivered from different azimuthal angles within the response area were flatter. These results suggest that the neural circuits underlying auditory spatial response properties of 1C neurons of monaural plugged bats undergone modifications to compensate for the unatural binaural disparity during postnatal development and the}' also suggest the importance of early auditory experence to postnatal development of central auditor}' system.3.Effects of GABA and bicuculline on auditor}' spatial response properties of inferior collicular neurons in juvenile and adult bats, Myotis chinensisUsing iontophoretic technique, we studied the effects of GABA and GABAA antagonist, bicuculline, on auditory spatial response properties of inferior collicular(IC) neurons in juvenile and adult bats, Myotis chinensis. The results showed that application of GABA increased the lowest minimum threshold(the lowest MT) of 1C neurons, broadened the auditory spatial response areas,sharpened the auditory spatial sensitivity curves as determined by variation of MT as a function of azimuthal angle and narrowed auditor}' spatial sensitivity curves as determined by variation of number of impulses as a function of azimuthal angle, while application of GABAA antagonist, bicuculline,reversed the above effecets.Furthermore,there was difference between the effects of GABA and bicuculline on the juvenile and adult bats. These data suggest that GABAergic inhibition play an important role on the form of auditory spatial response properties of 1C neurons and the changes of the GABAergic inhibition can modify the auditory spatial response areas and spatial sensitivities of 1C neurons.4.Effects of monaural plugging on the distribution of GABA-immunopositive neurons in the inferior colliculus of bat, Myotis chinensisIn order to explore the...