The Effects of Choline Supplements on Acquisition and Extinction of the Conditioned Eyeblink Response in Young Rats

Abstract

<p>Choline is an essential nutrient for basic biological functions in humans, but also is critical for learning and memory functions mediated by the hippocampus (Meck, Williams, Cermak, & Blusztagn, 2008). More recently, a neural protective role for choline has been suggested against developmental cognitive impairments resulting from fetal alcohol exposure (Wagner & Hunt, 2006). Much work has been done with prenatal supplements of choline, but more is needed to understand effects of postnatal supplementation. In the present study, we used a motor learning task that involves the hippocampus. We hypothesized that choline would enhance acquisition of trace eye-blink conditioning in developing rat pups and create memories more resistant to extinction than for control rats treated with saline. Pups were randomly assigned to receive daily injections of either choline chloride or saline vehicle from postnatal day (PND) 15-25. On PND 26, pups underwent surgery to implant electrodes for eyeblink conditioning. On PND 28-31, they received 6 sessions of conditioning over two days followed by four sessions of extinction over two days. During conditioning a 380 ms tone CS (2.8 kHz, 90dB) was followed by a 500 ms stimulus-free "trace" period and then a lOOms periorbital shock US (1.5 mAl. Half of the pups in each drug condition underwent extinction with CS-alone trials and the other half experienced extinction using unpaired CS and US presentations. The data indicate that acquisition was similar for both drug treatment groups. However, a significant main effect of extinction type was observed such that unpaired extinction was slower than CS-alone extinction. Furthermore, a significant Drug x Sex x Session interaction indicated that cholinetreated females showed considerable spontaneous recovery between Day 1 and Day 2 of extinction and had more difficulty overall in extinguishing their response compared to other groups.</p><p>This presentation occurred at the Wright State University Campus-Wide Celebration of Research, Scholarship and Creative Activities on April 8, 2011</p>