[Abstract Title]. - Society for Neuroscience

Title: Prenatal choline supplementation enhances the amplitude of hippocampal ripple/high
frequency events and increases the percentage of their occurrence during SWS and REM sleep
states
Authors: *W. H. MECK, C. L. WILLIAMS, R. K. CHENG;
Psychol & Neurosci, Duke Univ., Durham, NC
Abstract: Prenatal choline availability has been shown to induce organizational changes in the
hippocampus that contribute to changes in cognition across the lifespan depending upon the
prenatal choline treatment (e.g., deprivation or supplementation). To determine the neural
mechanism(s) for these cognitive effects, we studied hippocampal local field potentials (LFPs) in
the range from 1-250 Hz as a function of prenatal choline availability and sex. Adult male and
female rats (14 mo) exposed during embryonic days 12-17 to choline deficiency (DEF n=6+6: 0
mmol/kg choline), choline sufficiency/control (CON n=6+6: 7.9 mmol/kg choline), or choline
supplementation (SUP n=6+6: 35.6 mmol/kg choline) were implanted unilaterally with a
stainless-steel wire array in the dentate gyrus of the hippocampus (A: -4.8 mm, L: +2.5 mm, and
V: -4.0 mm to Bregma). An EMG patch was sutured in the nuchal muscle for chronic recording.
LFP data were recorded on multiple days that included 5 baseline sleep recording sessions as
well as one additional short session that contained exploration of novel objects for 1 hr followed
by 2 hours of sleep recording. By filtering the raw LFP traces in the frequency range between
100-250 Hz, we were able to identify ripple events (5 SD above the average root-mean square,
RMS) and high frequency events (HFE, 3 SD above the average RMS) from all treatment
groups. Results showed that the amplitude of the ripple/HFE (defined as the distance between the
peak and the trough of the filtered LFP traces) in the SUP rats is higher than both CON and DEF
groups. Furthermore, the occurrence of ripple/HFE is higher during REM sleep and SWS states
in the SUP rats. Finally, after the exploration of novel objects in the recording environment, all 6
groups showed an increased percentage of SWS and REM sleep that contain ripple/HFE events
with an even stronger increase for the SUP rats during REM sleep. Recent evidence suggests that
the ripple/HFE might be the neural substrate that reflects the process and/or provides the time
window for inducing synaptic plasticity and information transfer from/to the hippocampus
following new experiences. In vitro studies have shown that ripple events can produce long-term
potentiation (LTP) while prenatal choline supplementation can reduce the threshold for inducing
LTP. In addition, sleep is also hypothesized to provide a preferential state for memory
consolidation, a process that co-occurs with hippocampal ripple events. In conclusion, we found
that the enhanced high-frequency oscillations in the SUP rats provide a plausible neural
mechanism that can account for the cognitive benefits of prenatal choline supplementation.
Disclosures: W.H. Meck , None; C.L. Williams, None; R.K. Cheng, None.
Poster
290. Animal Cognition and Behavior: Learning and Memory: Pharmacology I