Abstract
The glucose (G) concentration in CSF is 2-3 mM and increases twice during food intake. When G was injected into the hippocampus to turn to 7 mM, spatial learning and memory were facilitated. To make clear this, neurophysiological measurement using hippocampal slice preparations were carried out. The G concentration in perfusate was changed from 3.5 to 7 mM for 15 min and returned to 3.5 mM. The CA1 synaptic potentials produced by Schaffer collateral stimuli were augmented, started from 3-4 min after the change to 7mM G. This augmentation continued for 40 min even after returning to 3.5 mM G. This was like a long-term potentiation (LTP) without a tetanic stimulation. LTP produced by tetanic stimulation (100 Hz, 1 s) just after returning to 3.5 mM G was significantly facilitated, while only short-term potentiation was produced in 3.5 mM G. Presynaptic transmitter release measured by paired pulse facilitation method and postsynaptic response to NMDA applied at the apical dendrites were also facilitated by 7 mM G. The membrane potential and input resistance were a little changed by 7 mM G. The phosphorylation of presynaptic synapsin I-3 and of postsynaptic CaMkII of CA1 neurons were facilitated by 7 mM G. These evidences indicate that food intake is necessary not only for keeping body homeostasis but also reinforcing the higher brain plasticity. [Jpn J Physiol 55 Suppl:S59 (2005)]
