Pre- and post-critical period induced reduction of Cat-301immunoreactivity in the lateral geniculate nucleus and visual cortex ofcats Y-blocked as adults or made strabismic as kittens

[摘要] Purpose: To test the post-critical period stability of perineuronalnets by comparing the expression of antigens on aggrecan (a chondroitinsulfate proteoglycan (CSPG) recognized by the monoclonal antibodyCat-301) in the lateral geniculate nucleus (LGN) and striate cortex(A17) of adult Y-blocked cats and cats made strabismic and amblyopic askittens. The comparison tested the idea that pre- and post-criticalperiod loss of synchronous activity would differentially affect theperineuronal net of Y-type neurons in LGN and A17.Methods: Seven adult cats, two normal, three convergent strabismicamblyopic, and two monocularly Y-blocked cats, were used in this study.The strabismic amblyopic cats had been made monocularly esotropic (bytenotomy) at 14 days of age. The Y-block was created acutely by apressure cuff placed on the optic nerve behind the left eye in adultcats. The efficacy of both procedures was tested electrophysiologically.Frontal frozen sections were incubated with the Cat-301 antibody and thelabeling visualized using a DAB kit. The sections were counterstainedwith cresyl violet. In each section, Cat-301-stained cells withwell-defined nucleoli were counted under a 20x objective with acomputer-based quantitative microscope image analysis system.Results: The percentage of positively labeled cells was reduced inLGN laminae that received input from the deviated eye in amblyopic catsand from the pressure-blocked eye in Y-blocked cats compared with normalcats. Surprisingly, the non-blocked laminae of the Y-blocked cats alsoshowed a significant reduction in positively labeled neurons whencompared to normals or to strabismic cats. In the visual cortex of bothhemispheres of strabismic and Y-blocked cats, the density ofimmunopositive neurons was significantly reduced compared with normal.The effect was most pronounced in layers IV-VI for Y-blocked cats and inlayer IV for strabismic amblyopic cats.Conclusions: The results demonstrate that surface expression ofaggrecan in adult cat LGN and A17 of adult cat is reduced both bychronic developmental loss of synchronous input from the two eyes and byacute changes in synchronous input in adulthood. Thus both pre- andpost-critical plasticity in the expression of epitopes of aggrecan canbe demonstrated. The uniform distribution of Cat-301 labelingtangentially within cortical layers of strabismic amblyopic catsindicates that the reduction in immunoreactivity observed withstrabismus induced early in life is not simply eye-specific. Indeed,comparison of the immunopositivity of Y-blocked and strabismic animals,both in LGN and cortex, suggests that even after the critical period isended, the physical removal of monocular Y-type afferent activity andweakening of binocular feedback connections between cortex and thalamuscan alter the stability of the perineuronal nets surrounding theaffected neurons.

[学科分类] 生物化学/生物物理