title: Pharmacological Rescue of Long-Term Potentiation in Alzheimer Diseased Synapses.
abstract: Long-term potentiation (LTP) is an activity-dependent and persistent increase in synaptic transmission. Currently available techniques to measure LTP are time-intensive and require highly specialized expertise and equipment, and thus are not well suited for screening of multiple candidate treatments, even in animal models. To expand and facilitate the analysis of LTP, here we use a flow cytometry-based method to track chemically induced LTP by detecting surface AMPA receptors in isolated synaptosomes: fluorescence analysis of single-synapse long-term potentiation (FASS-LTP). First, we demonstrate that FASS-LTP is simple, sensitive, and models electrically induced LTP recorded in intact circuitries. Second, we conducted FASS-LTP analysis in two well-characterized Alzheimer's disease (AD) mouse models (3xTg and Tg2576) and, importantly, in cryopreserved human AD brain samples. By profiling hundreds of synaptosomes, our data provide the first direct evidence to support the idea that synapses from AD brain are intrinsically defective in LTP. Third, we used FASS-LTP for drug evaluation in human synaptosomes. Testing a panel of modulators of cAMP and cGMP signaling pathways, FASS-LTP identified vardenafil and Bay-73-6691 (phosphodiesterase-5 and -9 inhibitors, respectively) as potent enhancers of LTP in synaptosomes from AD cases. These results indicate that our approach could provide the basis for protocols to study LTP in both healthy and diseased human brains, a previously unattainable goal.
  
  
  
  Learning and memory depend on the ability of synapses to strengthen in response to activity. Long-term potentiation (LTP) is a rapid and persistent increase in synaptic transmission that is thought to be affected in Alzheimer's disease (AD). However, direct evidence of LTP deficits in human AD brain has been elusive, primarily due to methodological limitations. Here, we analyze LTP in isolated synapses from AD brain using a novel approach that allows testing LTP in cryopreserved brain. Our analysis of hundreds of synapses supports the idea that AD-diseased synapses are intrinsically defective in LTP. Further, we identified pharmacological agents that rescue LTP in AD, thus opening up a new avenue for drug screening and evaluation of strategies for alleviating memory impairments.
authors.affiliation: Institute for Memory Impairments and Neurological Disorders and aleph.prieto@uci.edu.
authors.forename: G Aleph
authors.identifier: 0000-0001-9517-6989
authors.initials: GA
authors.lastname: Prieto
authors.affiliation: Department of Psychiatry and Human Behavior, University of California-Irvine, Irvine, California 92697, and.
authors.forename: Brian H
authors.identifier: 0000-0002-2201-090X
authors.initials: BH
authors.lastname: Trieu
authors.affiliation: Institute for Memory Impairments and Neurological Disorders and.
authors.forename: Cindy T
authors.identifier: 0000-0003-0107-8435
authors.initials: CT
authors.lastname: Dang
authors.affiliation: School of Nursing, University of California-Los Angeles, Los Angeles, California 90095.
authors.forename: Tina
authors.identifier: 0000-0002-4855-3953
authors.initials: T
authors.lastname: Bilousova
authors.affiliation: School of Nursing, University of California-Los Angeles, Los Angeles, California 90095.
authors.forename: Karen H
authors.identifier: 0000-0001-8218-9684
authors.initials: KH
authors.lastname: Gylys
authors.affiliation: Institute for Memory Impairments and Neurological Disorders and.
authors.forename: Nicole C
authors.initials: NC
authors.lastname: Berchtold
authors.affiliation: Department of Psychiatry and Human Behavior, University of California-Irvine, Irvine, California 92697, and.
authors.forename: Gary
authors.initials: G
authors.lastname: Lynch
authors.affiliation: Institute for Memory Impairments and Neurological Disorders and.|Department of Neurology and.|Department of Neurobiology and Behavior, University of California-Irvine, Irvine, California 92697.
authors.forename: Carl W
authors.initials: CW
authors.lastname: Cotman
mesh_terms: D000544:Alzheimer Disease / Q000503:physiopathology*; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology; D004558:Electric Stimulation; D005434:Flow Cytometry; D006801:Humans; D017774:Long-Term Potentiation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*; D013574:Synaptosomes / Q000187:drug effects
chemical_list: D010726:Phosphodiesterase Inhibitors; D018091:Receptors, AMPA; D000242:Cyclic AMP; D006152:Cyclic GMP
keywords: Alzheimer's disease; GluA1; LTP; flow cytometry; phosphodiesterase inhibitors; synaptosomes