TRAINING IN CHICKS ALTERS PSA-N-CAM DISTRIBUTION IN FOREBRAIN CELL-MEMBRANES

THE intermediate and medial hyperstriatum ventrale (IMHV) in the chick is involved in memory formation following one-trial passive avoidance training. Possible links between neural cell adhesion molecule (N-CAM ) distribution and memory consolidation were examined in an immunoelec tron microscope study of IMHV 6 h after training. An antibody against alpha 2,8 polysialic acid (PSA), characteristic for embryonic N-CAM, a nd one against the protein backbones of N-CAM were labelled (post-embe dding), separately, with 15 nm immunogold, and binding to their epitop es was analysed using the statistics of point processes. No difference in labelling levels between control and trained chicks, for either an tibodies, was found, both groups of birds showing that cell membrane r egions are 10-30 times more enriched in N-CAM isoforms, and have a two -fold greater proportion of PSA-N-CAM, than tissue as a whole. However , 375-400 nm regular arrays of labelled PSA-N-CAM were revealed statis tically in cell membranes of control, but not trained, chicks, which m ay be related to the possible involvement of such membrane PSA domains in memory-related neuroplasticity.