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Objective To determine the likelihood of G-protein coupled receptor 56 (GPR56 ) induces axonal development and myelination in the corpus callosum of mouse brain.Methods A total of 64 Gpr56 +/-and Gpr56 -/-mice were selected and randomly divided into two groups:Gpr56 +/-group (n=32)and Gpr56 -/-group (n=32).According to number of days after birth,each group was further divided into 4 subgroups including P7d,P14d,P21d and P28d subgroups.Levels of neurofilament-200 (NF -200)and proteolipid protein (PLP ) of myelin basic protein in corpus callosum were measured with immunohistochemistry staining and Western blot in P7d、P14d、P21d、P28d Gpr56 +/- and Gpr56 -/-mice.Gpr56 +/-and Gpr56 -/-neurons were cultured using P1 d Gpr56 +/-and Gpr56 -/-mouse brain.The lengths of Gpr56 +/- and Gpr56 -/-neuronal axon were measured and compared with Image J software. Axonal myelination in the corpus callosum of mouse brain in each group was observed under electronic microscopy and the axonal diameters between subgroups were compared.Results The levels of NF-200 and PLP in the corpus callosum in P7d、P14d、P21d、P28d Gpr56 -/-mice decreased significantly compared with Gpr56 +/- mice.The length of Gpr56 -/-neuronal axon was shortened compared with Gpr56 +/-neuronal axon.The number of myelinated axons was obviously reduced in the corpus callosum in P28d Gpr56 -/-mice.The diameter of axon in the corpus callosum of P28d Gpr56 +/-mouse is longer than that of P28d Gpr56 -/-mouse. Conclusions GPR56 may be involved in axonal development and myelination in the corpus callosum of mouse brain.
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Background Neurofilament 200 (NF200) is an indirect indicator of the specific distribution of axons.It reflects the condition of the maintenance of neuronal morphology.Whether NF200 is involved in the damage of the visual pathway after retinal ischemia reperfusion injury (RIRI) should be further examined.Objective The present study was to investigate the expression of NF200 in retinal ganglion cells (RGCs),lateral geniculate nucleus (LGN),superior colliculus and visual cortex following RIRI.Methods Forty SD rats were randomized into the RIRI 1-,2-,3-,4-,6-,8-week groups,sham operation group and control group.Acute intraocular hypertension was induced in the right eye by anterior chamber perfusion of normal saline solution for 60 minutes to elevate the intraocular pressure to 110 mmHg.The animals were sacrificed at different time points for the preparation of the retina,LGN,superior colliculus and visual cortex sections.The expression of NF200 in RGCs,LGN,superior colliculus and visual cortex was assayed by immunohistochemistry.Results The expression level (A value) of NF200 in the RGCs was significantly different among the 8 groups after reperfusion (F =78.855,P =0.000),and that in the 1-week group was significantly lower than in the control group (t =36.563,P＜0.01).In the RIRI 1-week group,the expression of NF200 in the contralateral LGN in the experimental group was significantly lower than that in the control group (t =6.483,P＜0.01).In the 4-week group and 6-week group,the expression of NF200 in the contralateral LGN was significantly higher than that in the control group (t =2.904,4.313,P＜0.01).One week after RIRI,the expression of NF200 in contralateral superior celliculus in the experimental group was significantly lower than that in the control group (t =2.966,P＜0.05),and in the 2-week group,the expression of NF200 in the contralateral superior colliculus was significantly higher than that in the control group (t =7.397,P＜0.01).In the 2-week group,3-week group and 4-week group,the expression of NF200 in bilateral visual cortex was significantly higher in the experimental group than that in the control group (contralateral ∶ t =18.728,18.213,15.088,P＜0.01 ; ipsilateral ∶ t =8.690,5.704,7.805,P＜0.01).Conclusions RIRI can induce axonal damage of RGCs,contralateral LGN,superior colliculus and bilateral visual cortex neurons.
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A central challenge in ischemia-induced neuronal death research is understanding the mechanisms by which apoptotic or necrotic cascades are initiated and affected. We tested potential roles for AMPA and NMDA receptor protein levels and activation of calpain, caspase-3 in the hippocampus at times after transient global ischemia when detectable necrotic or apoptotic cell damage was observed by neurofilament 200 (NF200) degradation, TUNEL, and H & E. We determined that the decrease in the AMPA receptor subunit, GluR2, in response to the transient global ischemia plays a major role in triggering the neuronal cell death in hippocampus. We also examined potential roles for calpain and caspase-3 in ischemic cell death and found that (1) calpain is activated at a time following caspase-3 activation and paralleled degradation of NR2A, NR2B, and GluR2 and irreversible necrotic neuronal changes, (2) caspase-3 is has their maximal expression at the time of highest apoptosis, (3) the NF200 degradation, one of the neuronal deathinducing factors was correlated well with the calpain activation and necrotic changes in the hippocampal CA1 neurons. These results suggest that the significant degradation of GluR2 subunits of AMPA receptor and calpain activation are possibly involved in NF 200 degradation-mediated necrotic hippocampal cell death after transient global ischemia.