Leung LS, Shen B, Ma J, Rajakumar N (2003) Cholinergic activity enhances hippocampal CA1 long-term potentiation during walking in rats. Neuroscience 2003 Abstracts 255.5. Society for Neuroscience, New Orleans, LA.
Summary: Long-term potentiation (LTP) at the basal dendrites of CA1 pyramidal cells was induced by a single 200-Hz stimulation train (0.5-1 sec duration) in freely behaving rats during one of four behavioral states – awake-immobility (IMM), walking, slow-wave sleep (SWS) and rapid-eye-movement sleep (REMS). Field excitatory postsynaptic potentials (fEPSPs) generated by basal dendritic excitation of CA1 were recorded before and up to 20 hours after the tetanus. Following a tetanus during any behavioral state, basal dendritic LTP was > 170% of the baseline for the first 30 min after the tetanus and decayed to ~125% at 20 hours after. LTP induced during walking was significantly larger than that induced during IMM, SWS or REMS. LTP induced during IMM, SWS and REMS was not significantly different from each other. To test the hypothesis that septohippocampal cholinergic activity enhanced LTP during walking than during immobility, rats were either pretreated with muscarinic cholinergic antagonist scopolamine (5 mg/kg i.p.) or given selective cholinotoxin IgG192-saporin in the medial septum. Pretreatment with scopolamine decreased the LTP induced during walking but did not affect that induced during IMM, such that the difference between LTP induced during walking and IMM was abolished. In IgG192-saporin injected rats, there was no difference in the LTP induced during walking and during IMM, and scopolamine did not reduce the LTP induced during walking. In contrast, sham-lesioned rats, like other control rats, showed larger LTP induced during walking than during IMM, and LTP induced during walking was attenuated by scopolamine. This appears to be the first demonstration of an enhancement of hippocampal LTP by physiologically activated septal cholinergic inputs. LTP of the CA3 to CA1 synapses may serve important behavioral functions.
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