title: Age-related deficit in behavioural extinction is counteracted by long-term ethanol consumption: correlation between 5-HIAA/5HT ratio in dorsal raphe nucleus and cognitive parameters.
abstract: We investigated age-related changes in learning and memory performance and behavioural extinction in the water maze; and in endogenous levels of serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) in the neocortex, hippocampus, thalamus and dorsal raphe nucleus of Wistar rats. Another aim was to assess the correlation between behavioural and biochemical parameters, which were measured in rodents of two different ages: 5 months (adults) and 16 months (middle-aged). The middle-aged subjects succeeded in learning the behavioural task, albeit with significantly worse performance when compared to adult animals. Aging also had significant main effects on memory and extinction. An age-dependent decrease in 5-HIAA levels was observed in both hippocampus and dorsal raphe nucleus (DRN). The decrease in DRN 5-HIAA was paralleled by a decrease in 5-HIAA/5-HT ratio in this brain area, which was significantly correlated to the animals' spatial memory performance and behavioural extinction. In addition, using middle-aged rats, a 2x2 factorial study was carried out to examine the effects of food restriction and chronic ethanol consumption on rat's performance in a spatial behavioural task and on central serotonergic parameters. None of these two treatments had a significant effect on the behavioural and biochemical parameters assessed, with the exception of extinction index, which was significantly affected by ethanol consumption. Long-term ethanol ameliorated the impairment in behavioural flexibility caused by aging. In conclusion, long-term ethanol consumption may have a role in protecting against age-related deficit in behavioural extinction. Moreover, the present results also indicate that DRN serotonergic system is involved in spatial memory and behavioural extinction.
authors.affiliation: Departamento de Bioquímica-Imunologia, Laboratório de Neurociência Comportamental e Molecular, LaNeC, Universidade Federal de Minas Gerais, Belo Horizonte 31270-010, Brazil.
authors.forename: Ieda F
authors.initials: IF
authors.lastname: Oliveira-Silva
authors.forename: Lucas
authors.initials: L
authors.lastname: Pinto
authors.forename: Silvia R C
authors.initials: SR
authors.lastname: Pereira
authors.forename: Vany P
authors.initials: VP
authors.lastname: Ferraz
authors.forename: Alfredo J A
authors.initials: AJ
authors.lastname: Barbosa
authors.forename: Vivian A A
authors.initials: VA
authors.lastname: Coelho
authors.forename: Felipe F A S
authors.initials: FF
authors.lastname: Gualberto
authors.forename: Valeria F
authors.initials: VF
authors.lastname: Souza
authors.forename: Rosiane R M
authors.initials: RR
authors.lastname: Faleiro
authors.forename: Glaura C
authors.initials: GC
authors.lastname: Franco
authors.forename: Angela M
authors.initials: AM
authors.lastname: Ribeiro
mesh_terms: D000375:Aging / Q000502:physiology*; D000428:Alcohol Drinking / Q000503:physiopathology*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D001923:Brain Chemistry / Q000187:drug effects; D002492:Central Nervous System Depressants / Q000008:administration & dosage; D004435:Eating / Q000187:drug effects / Q000502:physiology; D000431:Ethanol / Q000008:administration & dosage; D005108:Extinction, Psychological / Q000187:drug effects / Q000502:physiology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism*; D008297:Male; D018782:Maze Learning / Q000502:physiology; D011903:Raphe Nuclei / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism*
chemical_list: D002492:Central Nervous System Depressants; D012701:Serotonin; D000431:Ethanol; D006897:Hydroxyindoleacetic Acid