聽(tīng)覺(jué)部分喪失同時(shí)會(huì)伴隨聽(tīng)覺(jué)過(guò)敏,，即對(duì)較大的、甚或中等程度的聲音靈敏度增強(qiáng),。這是有點(diǎn)兒矛盾的現(xiàn)象,，其機(jī)制尚不清楚，而這種現(xiàn)象的確是由聲音造成的痛苦,，就像創(chuàng)傷性聲音對(duì)聽(tīng)覺(jué)正常的人所造成的痛苦一樣,。
現(xiàn)在，在分離出的大鼠耳蝸中用千兆歐姆封接光纖內(nèi)記錄及燃料標(biāo)記方法所做實(shí)驗(yàn),，確定長(zhǎng)期很神秘的II型耳蝸傳入神經(jīng)元為指示創(chuàng)傷性聲音的一個(gè)潛在通道,。這些神經(jīng)元從耳蝸外毛細(xì)胞接收突觸輸入，并以與體細(xì)胞C-纖維相似的方式被ATP激發(fā)（ATP已知在組織損傷期間會(huì)被釋放出來(lái)）,。在音量很高的創(chuàng)傷性聲音下,，毛細(xì)胞活動(dòng)與所釋放的ATP相結(jié)合，可能會(huì)為這些在解剖學(xué)上比較獨(dú)特的II型耳蝸傳入神經(jīng)元提供充分“刺激”,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature 461, 1126-1129 (22 October 2009) | doi:10.1038/nature08487
The postsynaptic function of type II cochlear afferents
Catherine Weisz1, Elisabeth Glowatzki1,2 & Paul Fuchs1,2
1 The Department of Neuroscience,
2 The Department of Otolaryngology-Head and Neck Surgery, The Center for Hearing and Balance and the Center for Sensory Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
4 Correspondence to: Paul Fuchs1,2 Correspondence and requests for materials should be addressed to P.F.
The mammalian cochlea is innervated by two classes of sensory neurons. Type I neurons make up 90–95% of the cochlear nerve and contact single inner hair cells to provide acoustic analysis as we know it. In contrast, the far less numerous type II neurons arborize extensively among outer hair cells (OHCs)1, 2 and supporting cells3, 4. Their scarcity and smaller calibre axons have made them the subject of much speculation, but little experimental progress for the past 50 years. Here we record from type II fibres near their terminal arbors under OHCs to show that they receive excitatory glutamatergic synaptic input. The type II peripheral arbor conducts action potentials, but the small and infrequent glutamatergic excitation indicates a requirement for strong acoustic stimulation. Furthermore, we show that type II neurons are excited by ATP. Exogenous ATP depolarized type II neurons, both directly and by evoking glutamatergic synaptic input5. These results prove that type II neurons function as cochlear afferents, and can be modulated by ATP. The lesser magnitude of synaptic drive dictates a fundamentally different role in auditory signalling from that of type I afferents.
