| Background and Objective:Visual cortex is the highest pivot of vision. All sorts of visual information which transmit through visual path to visual cortex, causing the variation of potential in the neurons of visual cortex, that eventually makes visual sense. At present, among the research about the reaction of rat's visual cortex to different flashing stimulations, existing ones mainly focus on the influence to visual induced potential by kinds of stimulate patterns. There is relatively little research in this respect, which concerning the impact on the spontaneous electrical activity by flashing stimulation to the field potential of neurons in visual pivot. The field potential of cortical neurons which reflect the spontaneous electrical activity of pyramidal cell in cerebral cortex, is the sum of PSP or field potential caused in the process of the synchronous activities by pyramidal cell in cerebral cortex. Flashing stimulations made by different colors has multifarious influences on rats'visual cortex. According to the present research, except for the insensitivity for red color, the rats can react to other light such as white light or all other monochromatic light and make the field potential of cortical neurons change. But to what kind of color the rat is most sensitive, there is no final conclusion so far. Most relevant experts think that the rat is more sensitive to the light of short wave such as UV-light. This phenomenon is possibly because of the mass intensity of optical photon, and partly has some relation to the type of the photoreceptor cell in the retina of the rats.Flashing stimulations have also made distinct influence on the field potential of the rats'visual cortex. It is presented by some report that increasing the intensity and frequency of the stimulation can result in posttetanic potentiation, PTP and even long-term potentiation, LTP.It is reported that the influence on the electrical activity of rats'visual cortex by the monochromatic light, is mainly by how the neural circuitry is altered, after the initial flash, to receive succeeding flashes in the photic stimulus train. This likely reflects alterations within recurrent feedback loops within cortex and thalamus and/or from cortex to thalamus, rather than a change in the direct excitatory connections in the ascending retino-geniculo-cortical pathway.But it is unclear that the specific mechanism of the field potentiation change induce by the different color photographic stimulation as well as the rats'color vision.The opsins of the murine cone cell can be mainly divided into two types, one of which is called M-opsin and the other is called UV-opsin. There are also researches which indicate that some of the rats'cone cell can express not only M-opsin, but also UV-opsin. almost all mammalian retina are present M-opsin, S-opsin is to determine whether rats with key photosensitive pigment color vision, The consequence of the rats'behavioral testing may well provide evidence for the existence of color vision in certain forms.This experiment is planed to using white light and other monochromatic light, which intend to discuss the influence of brain electrical activity of the rats'visual cortex and even possible long-term potentiation, LTP by the light stimulations, will enhance the recognization to the plasticity of the central nervous system, and eventually lay the first stone for the research to cerebral cognitive function. In order to understanding the influence of the monochromatic light to the electrical activity of rats'primary visual cortex. Methods:1 Electrophysiological experiments:10 healthy adult SD rats, weighing 180g-220g, either male or female. Intraperitoneal injection of chloral hydrate anesthesia, exposing the skull, brain anatomical mapping in reference to the primary visual cortex Vl area (6.8-7.0mm posterior to lambda,2.0mm lateral), recording electrodes were placed in the Vl area, reference electrode El (2.0mm anterior to lambda,2.0mm lateral) fixed on the frontal lobe, both the E2 (-2.0mm anterior to lambda,2.0mm lateral) as a reference, denture powder fixed.5,7,9 d after the first line in the EEG signal acquisition. Rats with implanted electrodes have been placed in the plexiglass box rat, mouse box in the wall to install light-emitting diode, respectively, rats were given white, red, green LED flash stimulation. Each record of about 2h, tracings before dark adaptation after 30min, and then turn to give white, red, green flash stimulation, stimulation of conversion between different color light, intermittent 30min, and also by the multi-channel physiological recorder records brain wave changes in District VI. Rats were measured after the first 5,7,9 d to give white, red, green,6s time before and after stimulation, and exploratory behavior in rats in the awake state..2 Immunohistochemistry2.1 Retinal photoreceptor protein Rhod-opsin and S-opsin expression:2.1.1 The adult SD rats were anesthetized, the eye quickly removed, frozen sections of continuous lines of double immunofluorescence retina:The first antibody are the mouse polyclonal anti-Rhod-opsin antibody (1:400) and rabbit anti-S-opsin monoclonal antibody (1:400), the secondary antibody are FITC-goat anti-mouse IgG (1:250) and TEXRED-goat anti-rabbit IgG (1:250).2.2.2 The adult SD rats were anesthetized with 4% paraformaldehyde perfusion eyeballs quickly removed, paraffin sections, The first antibody is the mouse polyclonal anti-Rhod-opsin antibody (1:400) and rabbit anti-S-opsin monoclonal antibody (1:400), the second antibody was goat anti-mouse IgG (1:250) and goat anti-rabbit IgG (1:250).2.2 The primary visual cortex photoreceptor protein S-opsin expression: 2.2.1 The adult SD rats were anesthetized, brains were removed, the primary visual cortex of a continuous line of frozen sections and immunofluorescence antibody technique identified the visual cortex of light-sensitive protein S-opsin:The first antibody is rabbit anti-S-opsin antibody (1:400),4℃overnight incubation, the secondary antibody is TEXRED-goat anti-rabbit IgG (1:250).2.2.2 The adult SD rats were anesthetized with 4% paraformaldehyde perfused brains were removed quickly, paraffin sections, The first antibody is anti-rabbit anti-S-opsin monoclonal antibody (1:400), the secondary antibody is goat anti-rabbit IgG (1:250.)Results:1. Electrophysiological experiments1.1 Field potential stimulation with different shade of change in the number of daysBrain wave amplitude and area of the test showed high correlation between that the 4 repeated measurement data, (P<0.01), group (correction) and between groups Analysis of variance showed that the time factor, and shade factors were significant interaction was significant (P<0.05), the amplitude and area of days shows the trends with repetitive stimulation, and this trend with the color vary light.1.2 Each experiment on field potential induced between the different shade of pairwise comparisonEach experiment on field potential induced between the different shade of pairwise comparison AT ay 5,compared before and after stimulation, a variety of shade caused by primary visual cortex area V1 brain wave amplitude and area of field potentials were no significant differences; at day 7, to stimulate the same shade, white, Green light field caused by the amplitude V1 area and area were significantly stronger than before (white, P<0.01; green, P<0.05), while white light was stronger than the red(P<0.05); at day 9,once again stimulated in the same shade, white, and green light cause the amplitude of field potentials V1 area and area were significantly stronger than before stimulation (P<0.01), the white and green light were significantly stronger than the red (P<0.01). Stimulation in all experiments at red light before and after showed no significant difference.1.3 The comparison of each shade of the field potentials at each day1.3.1 To white light At day 9, Vl field potential amplitude and area were significantly stronger than before stimulation and day 5, (days 7,9 VS before stimulation P<0.01, days 7,9 VS day 5, P<0.05), there was no significant differences between other groups.1.3.2 To green light At day 7and 9, Vl field potential amplitude and area were significantly stronger than before stimulation, (days 7 VS before stimulation P<0.05, days 9 VS before stimulation, P<0.01,and the area,days 7 and 9 VS before stimulation, P<0.01), there was no significant differences between other group.1.3.3 To red light There was no significant differences between all groups at each experiment days.2. Immunohistochemistry results2.1 Retinal photoreceptor protein Rhod-opsin and S-opsin expression is positive.2.2 The expression of S-opsin in Primary visual cortex in is positive.Summary:1 White and green flashing stimulation can enhance the electrical activity in rats' primary visual cortex, Suggesting sensitization and post-tetanic potentiation of primary visual cortex.2 There is no obvious effect on the electrical activity in the rats primary visual cortex electrical activity to red flashing stimilation.3 There is no significant difference between white and green flash.4 Expression Rhod-opsin and S-opsin in the rats'retinal, and expression S-opsin in rats' primary visval cortex5 Rat may has a form of color vision. |
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