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Charges in electrophysiological and morphological properties of neurons durirng the development of the visual cortex in the rat

TU Ya- Li , LIU Ying Binge, ZHANG Li, ZHAO YanJun, Wang Lei, HU Zhi- An

'Department of Ophthalmology, Southwest Hospital, Third Military Medical University, Chongqing400038. and Department of Physiology, Pharmacology, and Histology and Embryology, West China University of Medical Science，Chengdu 610041A

Abstract

To investigate the intracellular mechanism of activity-dependent synapses formation and redistribution，we studied the elect rophysiological and morphological characteristics of neurons of the developing visual cortex，and observed the level of synchronism of age and changes in the properties.Whole
cell patch-clamp recordings and intracellular biocytin staining were used to record postsynaptic currents (PSCs) from neurons in the visual cortex of Sprague- Dawley rats(postnatal d 4一28).The histological processing was made .There were three types of PSCs in 156 cells:silent response，monosynaptic response and polysynaptic response，during the first developmental month .Before eyes opened the number of the neurons with the silent response(57. 3%)was significantly higher than that after the eyes opened
(11·9%)(P<0. 001).However，the incidence of polysynaptic PSCs increased from 12. 4%before eyes opened to 28·9%after eyes opened(P<0. 01).During postnatal week 1，all cells were classified as immature·The immature cells had very high input resistances(RN>1·0 Gt2)，low amplitude(一0. 87mA) and short decay time(一0. 98 ms).During postnatal week 4，all cells were mature with lower in-
put resistance(RN<310 M Q)，larger amplitude(一6 6 m A)，and longer decay time(一225 ms).From postnatal weeks 1 to 3，the cells had elect rophysiological properties that were intermediate between the immature and mature types of cells.With biocytin intracellular staining，five types of neurons were ob-
tained:nvramidal cells，satellite cells，basket cells，neuroEllial cells and immature cells.On the basis of their elect rophysiological and morphological characteristics，pyramidal cells were classified into three cate-
gories:i m mature，inte r me diate，and mature cell types·During postnatal week 1，cells were immature with very high input resistance .Morphologically immature cells had short simple dendritic arborizations which incompletely penetrated the layer where the cell body lies .From postnatal weeks 2 to 4，the cells were mature with low input resistance .They were morphologically more complex with dendritic arborizations which completely penetrated the whole layers of the visual cortex .From postnatal weeks 1 to 2，a third，intermediate cell type had elect rophysiological properties that were intermediate between the immature and mature cell types.Three distinctive types of pyramidal cells in visual cortex only co-exist during postnatal weeks 1 to 2 .Data show that activity- dependent synapes are formed and integrated into local neuronal networks with visual stimulation.In the critical period of visual development，the level of synchronism of age and changes in electrophysiological and morphological properties in the visual cortex is
higher than that in the subcortex.

Key words: whole cell recording;patch clamp;Brain slice;Visual cortex;biocytin

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Citing This Article：

TU Ya- Li , LIU Ying Binge, ZHANG Li, ZHAO YanJun, Wang Lei, HU Zhi- An. Charges in electrophysiological and morphological properties of neurons durirng the development of the visual cortex in the rat. Acta Physiol Sin 2003; 55 (2): (in Chinese with English abstract).