title: Dynorphins regulate the strength of social memory.
abstract: Emotionally arousing events like encounter with an unfamiliar con-species produce strong and vivid memories, whereby the hippocampus and amygdala play a crucial role. It is less understood, however, which neurotransmitter systems regulate the strength of social memories, which have a strong emotional component. It was shown previously that dynorphin signalling is involved in the formation and extinction of fear memories, therefore we asked if it influences social memories as well. Mice with a genetic deletion of the prodynorphin gene Pdyn (Pdyn(-/-)) showed a superior partner recognition ability, whereas their performance in the object recognition test was identical as in wild-type mice. Pharmacological blockade of kappa opioid receptors (KORs) led to an enhanced social memory in wild-type animals, whereas activation of KORs reduced the recognition ability of Pdyn(-/-) mice. Partner recognition test situation induced higher elevation in dynorphin A levels in the central and basolateral amygdala as well as in the hippocampus, and also higher dynorphin B levels in the hippocampus than the object recognition test situation. Our result suggests that dynorphin system activity is increased in emotionally arousing situation and it decreases the formation of social memories. Thus, dynorphin signalling is involved in the formation of social memories by diminishing the emotional component of the experience.
authors.affiliation: Institute of Molecular Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, 53125 Bonn, Germany. Electronic address: abilkei@uni-bonn.de.
authors.forename: A
authors.initials: A
authors.lastname: Bilkei-Gorzo
authors.affiliation: Institute of Molecular Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, 53125 Bonn, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Mauer
authors.affiliation: Institute of Molecular Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, 53125 Bonn, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Michel
authors.affiliation: Institute of Molecular Psychiatry, University of Bonn, Sigmund-Freud-Str. 25, 53125 Bonn, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Zimmer
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology; D000679:Amygdala / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D004745:Enkephalins / Q000235:genetics* / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D011498:Protein Precursors / Q000235:genetics* / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D021641:Recognition, Psychology / Q000187:drug effects / Q000502:physiology*; D012919:Social Behavior
chemical_list: D004745:Enkephalins; D009292:Narcotic Antagonists; D011498:Protein Precursors; D017473:Receptors, Opioid, kappa; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; C033660:preproenkephalin
keywords: Dynorphin immunoreactivity; NorBNI; Object recognition; Social recognition; U-50488