The classically conditioned eyeblink response is one of the most advanced models for understanding the neural mechanisms underlying associative learning and disease states such as Alzheimer's dementia. Classical conditioning is an example of associative learning that occurs when a reinforcing unconditioned stimulus (US) is contingent on the occurrence of a preceding conditioned stimulus (CS). These studies are usually carried out in behaving rabbits which presents numerous challenges for experiments aimed at determining cellular mechanisms that produce conditioning. To facilitate such studies, we have developed an in vitro brain stem preparation from turtles that demonstrates a neural correlate of eyeblink classical conditioning. When auditory nerve electrical stimulation (the """"""""tone"""""""" CS) is paired with trigeminal nerve stimulation (the """"""""airpuff' US) a burst discharge is recorded in the abducens nerve which represents a blink response. The present project is aimed at investigation of the cellular mechanisms underlying conditioning. We will build on our previous findings suggesting that not only is postsynaptic trafficking of glutamate receptor subunits critical to conditioning, but that coordinate presynaptic remodeling occurs to facilitate neurotransmitter release. The following Specific Aims will be examined: To investigate the role of protein kinases CaMKII, PKA, PKC, and MARK in the induction and expression of in vitro abducens conditioning. To examine glutamate receptor trafficking at synaptic sites during in vitro conditioning. To perform intracellular recordings of abducens motor neurons to examine intrinsic properties and synaptic potentials in control and conditioned preparations. And, to determine a role for the immediate early genes (lEGs) Arc and Egr-1 in in vitro conditioning. The insights gained into basic processes of learning and memory will have fundamental implications for understanding memory disorders such as occur in amnesia and Alzheimer's disease.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IFCN-A (04))
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Babcock, Debra J
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University of South Dakota
Schools of Medicine
United States
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Zheng, Zhaoqing; Ambigapathy, Ganesh; Keifer, Joyce (2017) MeCP2 regulates Tet1-catalyzed demethylation, CTCF binding, and learning-dependent alternative splicing of the BDNF gene in Turtle. Elife 6:
Keifer, Joyce; Tiwari, Neeraj K; Buse, Leah et al. (2017) Subunit-specific synaptic delivery of AMPA receptors by auxiliary chaperone proteins TARP?8 and GSG1L in classical conditioning. Neurosci Lett 645:53-59
Keifer, Joyce; Zheng, Zhaoqing (2015) Coincidence detection in a neural correlate of classical conditioning is initiated by bidirectional 3-phosphoinositide-dependent kinase-1 signalling and modulated by adenosine receptors. J Physiol 593:1581-95
Ambigapathy, Ganesh; Zheng, Zhaoqing; Keifer, Joyce (2015) Regulation of BDNF chromatin status and promoter accessibility in a neural correlate of associative learning. Epigenetics 10:981-93
Keifer, Joyce; Zheng, Zhaoqing; Ambigapathy, Ganesh (2015) A MicroRNA-BDNF Negative Feedback Signaling Loop in Brain: Implications for Alzheimer's Disease. Microrna 4:101-8
Zheng, Zhaoqing; Keifer, Joyce (2014) Sequential delivery of synaptic GluA1- and GluA4-containing AMPA receptors (AMPARs) by SAP97 anchored protein complexes in classical conditioning. J Biol Chem 289:10540-50
Ambigapathy, Ganesh; Zheng, Zhaoqing; Keifer, Joyce (2014) Genomic organization and identification of promoter regions for the BDNF gene in the pond turtle Trachemys scripta elegans. J Mol Neurosci 53:626-36
Ambigapathy, Ganesh; Zheng, Zhaoqing; Li, Wei et al. (2013) Identification of a functionally distinct truncated BDNF mRNA splice variant and protein in Trachemys scripta elegans. PLoS One 8:e67141
Li, W; Keifer, J (2012) Rapid enrichment of presynaptic protein in boutons undergoing classical conditioning is mediated by brain-derived neurotrophic factor. Neuroscience 203:50-8
Zheng, Zhaoqing; Sabirzhanov, Boris; Keifer, Joyce (2012) Two-stage AMPA receptor trafficking in classical conditioning and selective role for glutamate receptor subunit 4 (tGluA4) flop splice variant. J Neurophysiol 108:101-11

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