title: Promoter-Specific Effects of DREADD Modulation on Hippocampal Synaptic Plasticity and Memory Formation.
abstract: Designer receptors exclusively activated by designer drug (DREADDs) are a novel tool with the potential to bidirectionally drive cellular, circuit, and ultimately, behavioral changes. We used DREADDs to evaluate memory formation in a hippocampus-dependent task in mice and effects on synaptic physiology in the dorsal hippocampus. We expressed neuron-specific (hSyn promoter) DREADDs that were either excitatory (HM3D) or inhibitory (HM4D) in the dorsal hippocampus. As predicted, hSyn-HM3D was able to transform a subthreshold learning event into long-term memory (LTM), and hSyn-HM4D completely impaired LTM formation. Surprisingly, the opposite was observed during experiments examining the effects on hippocampal long-term potentiation (LTP). hSyn-HM3D impaired LTP and hSyn-HM4D facilitated LTP. Follow-up experiments indicated that the hSyn-HM3D-mediated depression of fEPSP appears to be driven by presynaptic activation of inhibitory currents, whereas the hSyn-HM4D-mediated increase of fEPSP is induced by a reduction in GABAA receptor function. To determine whether these observations were promoter specific, we next examined the effects of using the CaMKIIα promoter that limits expression to forebrain excitatory neurons. CaMKIIα-HM3D in the dorsal hippocampus led to the transformation of a subthreshold learning event into LTM, whereas CaMKIIα-HM4D blocked LTM formation. Consistent with these findings, baseline synaptic transmission and LTP was increased in CaMKIIα-HM3D hippocampal slices, whereas slices from CaMKIIα-HM4D mice produced expected decreases in baseline synaptic transmission and LTP. Together, these experiments further demonstrate DREADDs as being a robust and reliable means of modulating neuronal function to manipulate long-term changes in behavior, while providing evidence for specific dissociations between LTM and LTP.
  
  
  CONCLUSIONS
  This study evaluates the efficacy of designer receptors exclusively activated by designer drug (DREADDs) as a means of bidirectionally modulating the hippocampus in not only a hippocampus-dependent task but also in hippocampal synaptic plasticity. This is the first study to evaluate the effects of DREADD-mediated inhibition and excitation in hippocampal long-term potentiation. More specifically, this study evaluates the effect of promoter-specific expression of DREADD viruses in a heterogenic cell population, which revealed surprising effects of different promoters. With chemogenetics becoming a more ubiquitous tool throughout studies investigating circuit-specific function, these data are of broad interest to the neuroscientific community because we have shown that promoter-specific effects can drastically alter synaptic function within a specific region, without parallel changes at the level of behavior.
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Alberto J
authors.initials: AJ
authors.lastname: López
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Enikö
authors.initials: E
authors.lastname: Kramár
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Dina P
authors.identifier: http://orcid.org/0000-0002-0324-8365
authors.initials: DP
authors.lastname: Matheos
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: André O
authors.initials: AO
authors.lastname: White
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Janine
authors.initials: J
authors.lastname: Kwapis
authors.affiliation: Davis M.I.N.D. Institute, University of California, Davis, Davis, California 96516.
authors.forename: Annie
authors.initials: A
authors.lastname: Vogel-Ciernia
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Keith
authors.identifier: http://orcid.org/0000-0002-8823-1510
authors.initials: K
authors.lastname: Sakata
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and.
authors.forename: Monica
authors.initials: M
authors.lastname: Espinoza
authors.affiliation: Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, California 92697, UC Irvine Center for Addiction Neuroscience, and mwood@uci.edu.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Wood
mesh_terms: D000818:Animals; D015198:Designer Drugs / Q000008:administration & dosage*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D000069473:Radiation Dose Hypofractionation; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
chemical_list: D015198:Designer Drugs; D009419:Nerve Tissue Proteins
keywords: DREADDs; long-term memory formation; long-term potentiation; object location memory; object recognition memory; theta-burst stimulation