Experience-dependent changes in the importance of N-methyl-D-aspartate (NMDA) receptors for visual transmission in superior colliculus.
The excitatory amino acid transmitter glutamate mediates visual activity in the superficial grey layer (SGS) of superior colliculus. At eye opening N-methyl-d-aspartate receptors (NMDA-rs) convey little of the visual response, but with age their role in visual transmission increases to a peak at P21, then falls to the lower adult level. Visual deprivation which begins before eye opening causes NMDA-rs to assume a greater importance for visual transmission in SGS. Here we explore the possibility that these experience-dependent changes in the role of NMDA-rs in the SGS are limited by age. We find that the effects of visual deprivation on NMDA-r mediated visual activity are recoverable even after extensive dark rearing. Also, a short episode of visual experience is sufficient to allow the normal situation to be established and subsequent dark rearing is ineffective. Four-day periods of visual experience beginning at P14 or P25 have the same effect. Given that NMDA-rs take little part in visual transmission prior to P18, these data prompt a reconsideration of the role of NMDA-r mediated sensory transmission in the mechanisms by which early environmental experience influences the development of the visual system.
Binns
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Department of Visual Science, Institute of Ophthalmology, University College London, Bath Street, London, ECIV 9EL, UK. k.binns@ucl.ac.uk
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D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000818:Animals; D003624:Darkness; D018507:Gene Expression Regulation, Developmental; D016202:N-Methylaspartate / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012683:Sensory Deprivation / Q000502:physiology*; D013477:Superior Colliculi / Q000254:growth & development / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid