Abstract
Abstract: :
Purpose: To study the experience-dependent synaptic plasticity on cells from different layers of rat visual cortex before and after eye-open day. Methods: The visual cortex slices were prepared from 35 Sprague-Dawley rats of both genders (4∼28 days). Bipolar stimulating electrodes were placed in white material of the visual cortex. Recording electrodes filled with 0.5% biocytin were positioned in II∼VI layers. Blind whole cell patch recording technique was adopted. Postsynaptic currents (PSCs) were evoked with interstimulus intervals of 0.1 Hz. Recordings were obtained using a voltage clamp amplifier and pClamp6 software. The neurons were stained after recording for the purpose of morphological study. Results: (1) There were three types of PSCs recorded from 156 cells: non-response PSCs, monosynaptic response PSCs and polysynaptic response PSCs, during the first postnatal month. Before the rat’s eye-open day, the ratio of the non-response PSCs recorded from neuron of visual cortex was significantly higher (57.3%) than those after the eye open (11.9%) (p<0.001). Meanwhile, the incidence of polysynaptic response PSCs was increased from12.4% before the eye open to 28.9% after eye open (p<0.01). (2) In layer IV after eye open, the input resistance of the neurons was decreased and the half-width of PSCs was prolonged (p<0.01) comparing with recordings before eye close period. The peak value, time of peak, 10∼90% rise time and 10-90% decay time of PSCs was increased significantly (p<0.05 ∼ p<0.001). The changes of input resistance and peak value of PSCs were also observed in layer II-III (p<0.001) after the rat eye open. (3) 23 cells were intracellular stained with Biocytin. The higher IR, more depolarized RMP, non-response or lower amplitude of PSCs was recorded from cells that were morphologically immature. Conclusion: (1) the conversion of silent synaptic responses to functional ones might play a major role in experience-dependent synaptic plasticity during development of the visual cortex. (2) The functional and morphological maturity of neurons in visual cortex of rat was coincided with age.
Keywords: 622 visual development • 520 plasticity • 394 electrophysiology: non-clinical