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L. Pitkänen, A. Urtti, P. Hakkarainen, A. Valjakka; Long–term Monitoring of the Visual Response Condition of the Retina, Superior Colliculus and Primary Visual Cortex of Freely Moving Non–drugged P23H and Control Rats . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5240.
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Purpose: To explore the visual response condition of the retina, contralateral superior colliculus (SC) and contralateral visual cortex of freely moving, rhodopsin gene mutant (P23H, line 3) and control albino rats (Spraque –Dawley), during the period of ageing. The effects of a single intravitreal injection of phosphate buffered saline (PBS) and basic fibroblast growth factor (bFGF) on visual capacity were also examined. Methods: Both the P23H and the control Sprague–Dawley rats were divided into three groups one of which was given a single injection of either bFGF or PBS intravitreally, at the age of three months. In each case, one group served as an uninjected control. For the recording of the retinal ERG and central field potential responses the rats were anesthetized for the permanent implantation of the recording electrodes on the scleral surface of the temporal side of the eye globe, within the optic layer of the SC and on the skull over the primary visual cortex. The types of electrodes implanted were silver ball–, thread– and screw–electrodes, respectively. A new method with the characterizing features of silver ball–electrodes and the visual stimulator device was applied in this investigation. Electric reponses to light flashes of twelve intensities were measured at the ages of 4 and 13 months from the three sites described. Results: The light responses were reproducibly recordable both from the eye (ERG) and from the brain sites at the two time points. The mutation in the rhodopsin gene was found to slightly and in relatively equal degrees reduce the sizes of light responses of both the retinal (a– and b–waves) and tectal/cortical areas at the two time points. Neither bFGF nor PBS was found to have any clear effects on visual responses. Ageing appeared to constantly depress the sizes of responses in all the sites of both groups. Conclusions: The data of this study demonstrated that by this new method it is possible to monitor the natural visual capacity of the retina and optic nerve for a practically unlimited time. A solitary bFGF injection does not seem to improve the retinal function of P23H rats.
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