1. Long-Term Potentiation and Excitability in the Hippocampus Are Modulated Differently by θ Rhythm
- Author
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Clayton S. H. Law and L. Stan Leung
- Subjects
Male ,Time Factors ,basal dendrites ,apical dendrites ,Long-Term Potentiation ,Biophysics ,Hippocampus ,Stimulation ,Hippocampal formation ,03 medical and health sciences ,0302 clinical medicine ,θ rhythm ,Animals ,Rats, Long-Evans ,Theta Rhythm ,030304 developmental biology ,Neurons ,0303 health sciences ,Analysis of Variance ,Confirmation ,Chemistry ,General Neuroscience ,population spike ,Long-term potentiation ,Population spike ,General Medicine ,Dendrites ,Electric Stimulation ,Rats ,Serotonin Receptor Agonists ,Cognition and Behavior ,1.6 ,Pyrazines ,Synaptic plasticity ,Excitatory postsynaptic potential ,NMDA receptor ,Nerve Net ,030217 neurology & neurosurgery - Abstract
Visual Abstract, Oscillations in the brain facilitate neural processing and cognitive functions. This study investigated the dependence of long-term potentiation (LTP), a neural correlate of memory, on the phase of the hippocampal θ rhythm, a prominent brain oscillation. Multichannel field potentials and current source-sinks were analyzed in hippocampal CA1 of adult male rats under urethane anesthesia. A single burst (five pulses at 200 Hz) stimulation of stratum oriens (OR) induced LTP of the basal dendritic excitatory sink (ES), which was maximal when the burst was delivered at ∼340° and ∼160° of the distal dendritic θ rhythm. Apical dendritic sink evoked by stratum radiatum (RAD) stimulation also showed biphasic maxima at ∼30° and ∼210° of the distal dendritic θ rhythm, about 50° phase delay to basal dendritic LTP. By contrast, maximal population spike (PS) excitability, following single-pulse excitation of the basal or mid-apical dendrites, occurred at a θ phase of ∼140°, and maximal basal dendritic ES occurred at ∼20°; γ (30–57 Hz) activity recorded in CA1 RAD had maximal power at ∼300° of the distal dendritic θ rhythm, different from the phases of maximal LTP. LTP induced during the rising θ phase was NMDA receptor sensitive. It is suggested that the θ phase modulation of CA1 PS excitability is mainly provided by θ-rhythmic proximal inhibition, while dendritic LTP is also modulated by dendritic inhibition and excitation, specific to basal and apical dendrites. In summary, basal and apical dendritic synaptic plasticity and spike excitability are facilitated at different θ phases in a compartmental fashion.
- Published
- 2018