title: Inactivation of muscarinic receptors impairs place and response learning: implications for multiple memory systems.
abstract: Extensive research has shown that the hippocampus and striatum have dissociable roles in memory and are necessary for place and response learning, respectively. Additional evidence indicates that muscarinic cholinergic receptors in the hippocampus and striatum exert an important role in the modulation of these memory systems. In our experiments, we assessed whether intact hippocampal and striatal muscarinic cholinergic transmission may be essential and/or necessary for place and response learning. We addressed these questions using administration of the muscarinic receptor antagonist, scopolamine, on both place and response learning in a food-rewarded T-maze task. The administration of scopolamine (15 μg or 30 μg) directly into the dorsal hippocampus impaired the performance of rats subjected to both place and cue-rich response version of the task, but did not affect the response version, when the task was performed under cue-poor conditions. However, the administration of scopolamine in the dorsolateral striatum impaired the cue-poor response version of the T-maze task without interfering with the place version or cue-rich response version. Taken together, these results indicate that activation of muscarinic cholinergic receptors in the hippocampus and striatum facilitate the use of different strategies of learning, thus strengthening the hypothesis of multiple memory systems. Additionally, these results emphasize the importance of the environmental conditions under which tasks are performed.
authors.affiliation: Departamento de Psicobiologia, Universidade Federal de São Paulo - UNIFESP, Rua Napoleão de Barros, 950, São Paulo, SP 04024-002, Brazil.
authors.forename: Juliana Carlota Kramer
authors.initials: JC
authors.lastname: Soares
authors.forename: Maria Gabriela Menezes
authors.initials: MG
authors.lastname: Oliveira
authors.forename: Tatiana Lima
authors.initials: TL
authors.lastname: Ferreira
mesh_terms: D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D008568:Memory / Q000187:drug effects* / Q000502:physiology*; D008845:Microinjections; D018727:Muscarinic Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011976:Receptors, Muscarinic / Q000502:physiology*; D012601:Scopolamine / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D012601:Scopolamine
keywords: Hippocampus; Maze; Muscarinic receptors; Place learning; Response learning; Scopolamine; Striatum