Isolichenan, an α-glucan isolated from lichen <i>Cetrariella islandica</i>, repaires impaired learning behaviors and facilitates hippocampal synaptic plasticity

Abstract

The acute effects of isolichenan, a homologous α-glucan (1-3)(1-4) (3:2) isolated from lichen Cetrariella islandica, on the hippocampal synaptic plasticity were investigated in rats in vivo. Isolichenan (1mg /kg, intravenous treatment) significantly enhanced short-term potentiation evoked by a subthreshold tetanus, without any effect on the basal synaptic excitability (no tetanus stimulation). No effects on a supra-threshold tetanus-evoked potentiation were found. Isolichenan did not influence learning behaviors of intact mice in passive-avoidance tests and of intact rats in the Morris water maze test. When the learning ability of mice was impaired by 30% ethanol pre-treatment, isolichenan (>100mg/kg, oral treatment) significantly improved memory acquisition in passive-avoidance tests. Similarly, isolichenan (100 mg/kg, oral treatment) repaired memory-impairment induced by β-amyloid peptide (fraction 25-35) in the Morris water maze test in rats. These results suggest positive effects of isolichenan on spatial memory formation in rodents.