title: M1 muscarinic receptors are necessary for retrieval of remote context fear memory.
abstract: Several studies have investigated the transition of consolidation of recent memory to remote memory in aversively motivated tasks, such as contextual fear conditioning (CFC) and inhibitory avoidance (IA). However, the mechanisms that serve the retrieval of remote memories, has not yet been fully understood. Some evidences suggest that the central cholinergic system appears be involved in the modulation of these processes. Therefore, the present study aimed to investigate the effects of a pre-test administration of dicyclomine, a high-affinity M1 muscarinic receptor antagonist, on the retrieval of remote memories in fear conditioning and IA tasks. Male Wistar rats were trained, and after 1 or 28days, the rats received dicyclomine (16 or 32mg/kg, intraperitoneally, i.p.) and were tested in CFC, tone fear conditioning (TFC) and IA tasks. At both time intervals, 32mg/kg dicyclomine induced impairment of CFC. In TFC task only the performance of the rats 28days after training was impaired. The IA task was not affected in any of the studied intervals. These findings suggest a differential contribution of muscarinic receptors on recent and remote memories retrieval revealing a more generalized role in remote memory.
authors.affiliation: Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, São Paulo, SP, Brazil.
authors.forename: Rafael Rodisanski
authors.initials: RR
authors.lastname: Patricio
authors.affiliation: Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, São Paulo, SP, Brazil. Electronic address: julianacarlota@gmail.com.
authors.forename: Juliana Carlota Kramer
authors.initials: JC
authors.lastname: Soares
authors.affiliation: Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, São Paulo, SP, Brazil.
authors.forename: Maria Gabriela Menezes
authors.initials: MG
authors.lastname: Oliveira
mesh_terms: D000161:Acoustic Stimulation / Q000009:adverse effects; D000704:Analysis of Variance; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D003214:Conditioning, Classical / Q000187:drug effects / Q000502:physiology*; D004025:Dicyclomine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000187:drug effects / Q000502:physiology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D013997:Time Factors
chemical_list: D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D004025:Dicyclomine
keywords: Acetylcholine; Fear conditioning; Inhibitory avoidance; M1 receptor; Memory retrieval; Remote memory