The role of spontaneous activity in development of the endbulb of Held synapse

• Published in: Hearing research Vol. 230; no. 1; pp. 53 - 63
• Main Authors: McKay, Sarah M., Oleskevich, Sharon
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-08-2007; Elsevier
• Subjects: Adult and adolescent clinical studies; Aging - metabolism; AMPA; Animals; Auditory; Auditory Pathways - growth & development; Auditory Pathways - metabolism; Auditory Pathways - physiopathology; Biological and medical sciences; Cochlear Nerve - growth & development; Cochlear Nerve - metabolism; Cochlear Nerve - physiopathology; Cochlear Nucleus - growth & development; Cochlear Nucleus - metabolism; Cochlear Nucleus - physiopathology; Deafness - genetics; Deafness - metabolism; Deafness - physiopathology; Depression; Development; dn/ dn; Ear, auditive nerve, cochleovestibular tract, facial nerve: diseases, semeiology; Electric Stimulation; Endbulb of Held; Evoked Potentials; Excitatory Postsynaptic Potentials; Hearing; In Vitro Techniques; Kinetics; Medical sciences; Mice; Mice, Inbred CBA; Mice, Neurologic Mutants; Mood disorders; Neural Conduction; Non tumoral diseases; Otorhinolaryngology. Stomatology; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Receptors, AMPA - metabolism; Spontaneous; Synapses - metabolism; Synaptic Transmission; Q av; Pr; Endbulb of Held; AMPA; P ves; Spontaneous; mEPSC; dn/ dn; N; eEPSC; RRP; Auditory; aCSF; Development; TTX; AVCN; Central nervous system; Auditory disorder; Auditory nucleus; Glutamate receptor; Auditory nerve; Inner ear; Organ of hearing; Encephalon; Postnatal; Synaptic transmission; ENT disease; dn/dn; Age; Release; Mood disorder; Hair cell of the ear; Cochlear nerve; Rodentia; Cochlear nucleus; Depression; Hearing loss; Vertebrata; Hearing; AMPA receptor; Mammalia; Mouse; Cochlea; Auditory pathway
• ISSN: 0378-5955; 1878-5891
• DOI: 10.1016/j.heares.2007.05.006

In the mouse brainstem cochlear nucleus, the auditory nerve to bushy cell synapse (endbulb of Held) is specialised for rapid, high-fidelity transmission. Development of this synapse is modulated by auditory nerve activity. Here we investigate the role of spontaneous auditory nerve activity in synaptic transmission using
deafness (
dn/
dn) mutant mice that have abnormal hair cells and lack spontaneous auditory nerve activity. Evoked and miniature alpha amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor-mediated excitatory post-synaptic currents (eEPSCs, mEPSCs) were compared in
deafness and normal mice before the age of hearing onset (postnatal day 7–11: P7–11) using variance-mean, miniature event and tetanic depression analyses. Amplitudes were significantly greater in
deafness mice for eEPSCs (2.1-fold), mEPSCs (1.4-fold) and quantal amplitudes (1.5-fold). eEPSCs in
deafness mice decayed more rapidly with increasing age, indicating an input-independent transition in post-synaptic AMPA receptor properties. A comparison of normal mice before and after the onset of hearing showed a change in synaptic parameters with an increase in eEPSC (1.7-fold), mEPSC (1.6-fold) and quantal amplitude (1.7-fold) after hearing onset while release probability remained constant (0.5). Overall, the results in
deafness mice suggest that synaptic strength is altered in the absence of spontaneous auditory nerve activity.