title: Melatonin administration impairs visuo-spatial performance and inhibits neocortical long-term potentiation in rats.
abstract: Melatonin has been shown to inhibit long-term potentiation (LTP) in hippocampal slices of rats. Since LTP may be one of the main mechanisms by which memory traces are encoded and stored in the central nervous system, it is possible that melatonin could modulate cognitive performance by interfering with the cellular and/or molecular mechanisms involved in LTP. We investigated in rats the effects of intraperitoneally-administered melatonin (0.1, 1 and 10 mg/kg), its saline-ethanol solvent, or saline alone, on the acquisition of visuo-spatial memory as well as on the ability of the cerebral cortex to develop LTP in vivo. Visuo-spatial performance was assessed daily in rats, for 10 days, in an 8-arm radial maze, 30 min after they received a single daily dose of melatonin. Visual cortex LTP was determined in sodium pentobarbital anesthetized rats (65 mg/kg i.p.), by potentiating transcallosal evoked responses with a tetanizing train (312 Hz, 500 ms duration) 30 min after administration of a single dose of melatonin. Results showed that melatonin impaired visuo-spatial performance in rats, as revealed by the greater number of errors committed and time spent to solve the task in the radial maze. Melatonin also prevented the induction of neocortical LTP. It is concluded that melatonin, at the doses utilized in this study, could alter some forms of neocortical plasticity involved in short- and long-term visuo-spatial memories in rats.
authors.affiliation: Laboratory of Hormones and Receptors, Institute of Nutrition and Food Technology (INTA), University of Chile, Santiago, Chile.
authors.forename: Rubén
authors.initials: R
authors.lastname: Soto-Moyano
authors.forename: Héctor
authors.initials: H
authors.lastname: Burgos
authors.forename: Francisco
authors.initials: F
authors.lastname: Flores
authors.forename: Luis
authors.initials: L
authors.lastname: Valladares
authors.forename: Walter
authors.initials: W
authors.lastname: Sierralta
authors.forename: Victor
authors.initials: V
authors.lastname: Fernández
authors.forename: Hernán
authors.initials: H
authors.lastname: Pérez
authors.forename: Paula
authors.initials: P
authors.lastname: Hernández
authors.forename: Alejandro
authors.initials: A
authors.lastname: Hernández
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D017774:Long-Term Potentiation / Q000187:drug effects*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D008550:Melatonin / Q000494:pharmacology*; D008568:Memory / Q000187:drug effects*; D019579:Neocortex / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D020318:Rats, Long-Evans; D011963:Receptors, GABA-A / Q000187:drug effects; D013028:Space Perception / Q000187:drug effects; D014796:Visual Perception / Q000187:drug effects
chemical_list: D011963:Receptors, GABA-A; D008550:Melatonin