The Electrophysiological And Morphological Properties Of Neurons Visual Cortex Of Binocular Deprivated Rat

Purpose: To study electrophysiological properties of neurons in visual cortex of binocular deprivated rats during the development and explore the synaptic and cellular mechanism of experience-dependent plasticity in the visual cortex. The relationship between morphological and functional maturation of neurons in visual cortex was studied with the biocytin.Methods: The visual cortex slices were prepared from 61 Wistar rats of both genders, which were divided into two groups: control group and binocular pattern deprivation (BD) group. In the control group, 32 rats were recorded at 3, 4 and 5 postnatal weeks. 13 rats were sacrified at 3 weeks of age (20~22days); 9 rats were sacrified at 4 weeks of age (27~29 days); 10 rats were sacrified at 5 weeks of age (34~36 days). In the BD group, 29 rats were recorded. 12 rats were sacrified at 3 weeks of age(20~22days); 9 rats were sacrified at 4 weeks of age (27~29 days) and 8 rats were sacrified at 5 weeks of age (34~36 days). Both eyelids were sutured at 13 days postnatal in BD group before the eyes open. Blind patch-clamp whole cell recording were adopted. Pre-synaptic test stimulation was given at 0.07 Hz intervals through bipolar stimulating electrodes. EPSCs of layer â…¡~â…£ were recorded by recording electrodes filled with 0.5% biocytin. Long-term potentiation (LTP) was induced by low-frequency stimulation (LFS) at 1Hz for 60~90 sec, each pulse of the LFS paired with depolarization of post-synaptic neurons to -20 mV. The neuronswere stained after recording for the purpose of morphological study.Results: 1. There were three types of PSCs recorded: silent synaptic response, monosynaptic response, and polysynaptic response. The percentage of silent response in BD group (20%) was significantly higher than that in the control group(3.17%) (P<0.01) , While the incidence of polysynaptic EPSCs in BD group(7.94%) was significantly lower than that in the control group(27.2%) (P<0.01). 2. Compared with those of control group , neurons in BD group has a increased input resistance, peak value of EPSCs, a more depolarized resting membrane potential (P<0.05), and the neurons were morphologically less mature. 3. The incidence of LTP induced in BD group was lower while the LTP magnitude significantly higher than that in control group. Conclusions: 1. The input resistance and the resting membrane potential are important to discriminate the mature state of the neurons.2.The incidence of polysynaptic EPSCs tends to increase gradually in control group, while there are much more silent synaptic responses in BD group. It suggests that the activation of silent synapse may relate to in formation of synaptic connections. 3. The electrophysiological and morphological properties of neurons are intimately correlated with each other. 3. The incidence of LTP induction was decreased in binocular deprivated rats suggests that the visual stimulation of patterns facilitate the maturing of the neurons in visual cortex. 5. The amplitude of LTP increased in BD group while the incidence of LTP induction was getting down compare with those of control one. It implys that the plasticity of neurons in visual cortex was decreased by BD, but the response ability to adequate stimulus still exist.