通常認(rèn)為,，年輕的大腦環(huán)路是具有很大的彈性的,，但最終在成年期變固定,。在11月8日的《神經(jīng)元》（Neuron）雜志上,，來自美國約翰·霍普金斯的研究人員報(bào)告說,，成年神經(jīng)元并沒有像我們推測的那樣牢牢固定在某個(gè)地方。
由David Linden教授領(lǐng)導(dǎo)的研究組利用一種稱為“雙光子顯微鏡”的新技術(shù)觀察了完整大腦中活神經(jīng)元的工作,。研究人員將熒光染料注射到小鼠大腦中,，以“照亮”神經(jīng)元亞群，然后通過一種在活小鼠的頭骨中構(gòu)建的“窗戶”來觀察這些神經(jīng)元,。
他們分析了利用延伸的纖維（軸突）給小腦發(fā)送信號的神經(jīng)元,，而小腦有助于協(xié)調(diào)運(yùn)動和感覺信息。軸突就好像不斷生長的樹一樣,，有主干和一些小的側(cè)枝,。但是，盡管主干緊緊的與小腦中其他靶標(biāo)神經(jīng)元聯(lián)結(jié)（成熟神經(jīng)元通常被認(rèn)為處于這種“靜止”狀態(tài)）,，但“側(cè)枝”像風(fēng)箏一樣在風(fēng)中搖擺,。在幾個(gè)小時(shí)的觀測過程中，單個(gè)側(cè)枝可以高動態(tài)模式拉長,、縮回和變形,。
這些側(cè)枝還不能與臨近的神經(jīng)元產(chǎn)生常規(guī)的聯(lián)系,，如突觸。而且,，當(dāng)使用一種能在軸突中產(chǎn)生強(qiáng)烈電流的藥物時(shí),，側(cè)枝的這種運(yùn)動就會停止。
Linden表示,，接下來要解決的問題就是為什么大腦需要這種活潑的,、非連接性的枝條。他認(rèn)為,，他們可能發(fā)現(xiàn)了在神經(jīng)發(fā)生過程中不依靠突觸進(jìn)行信息傳遞的第二個(gè)機(jī)制,。能夠獲得活腦中突觸實(shí)時(shí)運(yùn)動畫面的能力為研究人員提供了一種分析軸突再生的強(qiáng)大工具。
原始出處:
Neuron, Vol 56, 472-487, 08 November 2007
Article
Axonal Motility and Its Modulation by Activity Are Branch-Type Specific in the Intact Adult Cerebellum
Hiroshi Nishiyama,1 Masahiro Fukaya,2 Masahiko Watanabe,2 and David J. Linden1,
1 Department of Neuroscience, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205, USA
2 Department of Anatomy, Hokkaido University School of Medicine, Sapporo 060-8638, Japan
Corresponding author
David J. Linden
[email protected]
We performed two-photon in vivo imaging of cerebellar climbing fibers (CFs; the terminal arbor of olivocerebellar axons) in adult mice. CF ascending branches innervate Purkinje cells while CF transverse branches show a near complete failure to form conventional synapses. Time-lapse imaging over hours or days revealed that ascending branches were very stable. However, transverse branches were highly dynamic, exhibiting rapid elongation and retraction and varicosity turnover. Thus, different branches of the same axon, with different innervation patterns, display branch type-specific motility in the adult cerebellum. Furthermore, dynamic changes in transverse branch length were almost completely suppressed by pharmacological stimulation of olivary firing.
