title: A cell adhesion molecule mimetic, FGL peptide, induces alterations in synapse and dendritic spine structure in the dentate gyrus of aged rats: a three-dimensional ultrastructural study.
abstract: The FGL peptide is a neural cell adhesion molecule (NCAM) mimetic comprising a 15-amino-acid-long sequence of the FG loop region of the second fibronectin type III module of NCAM. It corresponds to the binding site of NCAM for the fibroblast growth factor receptor 1. FGL improves cognitive function through enhancement of synaptic function. We examined the effect of FGL on synaptic and dendritic structure in the brains of aged (22-month-old) rats that were injected subcutaneously (8 mg/kg) at 2-day intervals until 19 days after the start of the experiment. Animals were perfused with fixative, brains removed and coronal sections cut at 50 microm. The hippocampal volume was measured, tissue embedded and ultrathin sections viewed in a JEOL 1010 electron microscope. Analyses were made of synaptic and dendritic parameters following three-dimensional reconstruction via images from a series of approximately 100 serial ultrathin sections. FGL affected neither hippocampal volume nor spine or synaptic density in the middle molecular layer of the dentate gyrus. However, it increased the ratio of mushroom to thin spines, number of multivesicular bodies and also increased the frequency of appearance of coated pits. Three-dimensional analysis showed a significant decrease in both post-synaptic density and apposition zone curvature of mushroom spines following FGL treatment, whereas for thin spines the convexity of the apposition zone increased. These data indicate that FGL induces large changes in the fine structure of synapses and dendritic spines in hippocampus of aged rats, complementing data showing its effect on cognitive processes.
authors.affiliation: Department of Biological Sciences, Faculty of Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK.
authors.forename: Victor I
authors.initials: VI
authors.lastname: Popov
authors.forename: Nikolay I
authors.initials: NI
authors.lastname: Medvedev
authors.forename: Igor V
authors.initials: IV
authors.lastname: Kraev
authors.forename: Paul L
authors.initials: PL
authors.lastname: Gabbott
authors.forename: Heather A
authors.initials: HA
authors.lastname: Davies
authors.forename: Marina
authors.initials: M
authors.lastname: Lynch
authors.forename: Thelma R
authors.initials: TR
authors.lastname: Cowley
authors.forename: Vladimir
authors.initials: V
authors.lastname: Berezin
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Bock
authors.forename: Michael G
authors.initials: MG
authors.lastname: Stewart
mesh_terms: D000375:Aging / Q000187:drug effects; D000818:Animals; D040761:Biomimetic Materials / Q000494:pharmacology*; D015815:Cell Adhesion Molecules / Q000494:pharmacology; D049229:Dendritic Spines / Q000187:drug effects / Q000648:ultrastructure*; D018891:Dentate Gyrus / Q000187:drug effects / Q000648:ultrastructure*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D019006:Neural Cell Adhesion Molecules / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000187:drug effects / Q000648:ultrastructure*
chemical_list: D015815:Cell Adhesion Molecules; C488618:NCAM protein (681-695), human; D019006:Neural Cell Adhesion Molecules