Effects of ginsenoside Rg(1) on synaptic plasticity of freely moving rats and its mechanism of action

AIM: To investigate the effect and mechanism of ginsenoside Rg(1) on synapt ic plasticity of freely moving rats. METHODS: SD rats were chronically impl anted with a stimulation electrode in the perforant path (PP) of hippocampu s and a recording electrode in the granule cell of dentate gyrus. After adm inistration of ginsenoside Rg(1) (10, 30 mg/kg, ip) for 12 d, extracellular recording technique was used to record the population spike (PS). Mossy fi ber (MF) sprouting was measured using Timm's staining, and an immunohistoch emical technique was used to detect the expression of presynaptic growth-as sociated protein 43 (GAP-43). RESULTS: Rg(1) could significantly increase t he sensitivity of evoking PS, the amplitude of PS and induce PP-DG long-ter m potentiation (LTP) in the dentate gyrus (DG) of freely moving rats. In th e meantime, Rg(1) accelerated MF sprouting in CA3 cell field of hippocampus . The expression level of GAP-43 was elevated in granule cell layer and hil us of DG of Rg(1)-treated rats. CONCLUSION: The increased synaptic plastici ty may attribute to the increased expression of GAP-43 in granule cell, lay er of DG and the onset of the sprouting of granule cell axon-MF. The MF spr outing accelerated the synaptic transmission in positive feedback. Their in teraction and the synergism is part of the mechanisms underlying the nootro pic effect of Rg(1).