title: Post-training cocaine exposure facilitates spatial memory consolidation in C57BL/6 mice.
abstract: In this study, we examined the ability of post-training injections of cocaine to facilitate spatial memory performance using the Morris water maze (MWM). We also investigated the role that hippocampal protein kinase A (PKA) and extracellular signal-regulated kinase 1/2 (ERK) signaling may play in cocaine-mediated spatial memory consolidation processes. Male and female C57BL/6 mice were first trained in a MWM task (eight consecutive trials) then injected with cocaine (0, 1.25, 2.5, 5, or 20 mg/kg), and memory for the platform location was retested after a 24 h delay. Cocaine had a dose-dependent effect on spatial memory performance because only the mice receiving 2.5 mg/kg cocaine displayed a significant reduction in latency to locate the platform. No sex differences in MWM performance were observed; however, females showed higher hippocampal levels of PKA when compared with males. A second experiment demonstrated that 2.5 mg/kg cocaine enhanced MWM performance only when administered within 2, but not 4 h after spatial training. We also found that cocaine (2.5 mg/kg) increased ERK2 phosphorylation within the hippocampus and one of its downstream targets (ribosomal S6 kinase), a mechanism that may be responsible, at least in part, for the enhanced cocaine-mediated spatial memory performance. Overall, these data demonstrate that a low dose of cocaine (2.5 mg/kg) administered within 2 h after training facilitates MWM spatial memory performance in C57BL/6 mice.
authors.affiliation: Department of Psychology, California State University, San Bernardino, California 92407, USA.
authors.forename: Sergio D
authors.initials: SD
authors.lastname: Iñiguez
authors.forename: Sergios
authors.initials: S
authors.lastname: Charntikov
authors.forename: Shelley A
authors.initials: SA
authors.lastname: Baella
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Herbert
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Bolaños-Guzmán
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Crawford
mesh_terms: D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D018782:Maze Learning / Q000187:drug effects* / Q000502:physiology; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D013997:Time Factors
chemical_list: D019893:Ribosomal Protein S6 Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D003042:Cocaine