title: Spatial learning-induced increase in agmatine levels at hippocampal CA1 synapses.
abstract: Agmatine, a metabolite of L-arginine, is considered as a novel putative neurotransmitter. It has been detected in axon terminals that synapse with pyramidal cells in the hippocampus, a brain region that is critically involved in spatial learning and memory. However, the role of agmatine in learning and memory is poorly understood. Recently, we demonstrated water maze training-induced increases in tissue levels of agmatine in the CA1 subregion of the hippocampus. This finding has raised an issue whether an endogenous agmatine could directly participate in learning and memory processes as a neurotransmitter. In the present study, quantitative immunogold-labeling and electron-microscopical techniques were used to analyze the levels of agmatine in CA1 stratum radiatum (SR) terminals (n = 600) of male Sprague-Dawley rats that had been trained to find a hidden escape platform in the water maze (WM) task or forced to swim (SW) in the pool with no platform presented. Agmatine levels were significantly increased by ∼85% in the synaptic terminals of SR of trained WM group compared with the SW control group (all P < 0.001). These results, for the first time, demonstrate spatial learning-induced elevation in agmatine levels at synapses in the hippocampus and provide evidence of its participation in learning and memory processing as a novel neurotransmitter.
authors.affiliation: Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand. beulah.leitch@anatomy.otago.ac.nz
authors.forename: Beulah
authors.initials: B
authors.lastname: Leitch
authors.forename: Olga
authors.initials: O
authors.lastname: Shevtsova
authors.forename: Katharina
authors.initials: K
authors.lastname: Reusch
authors.forename: David H
authors.initials: DH
authors.lastname: Bergin
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
mesh_terms: D000376:Agmatine / Q000378:metabolism*; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology*; D008297:Male; D018782:Maze Learning / Q000502:physiology*; D016253:Microscopy, Immunoelectron / Q000379:methods; D051381:Rats; D017207:Rats, Sprague-Dawley; D013037:Spatial Behavior / Q000502:physiology*; D013550:Swimming; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000376:Agmatine