title: TRH injected into the nucleus accumbens shell releases dopamine and reduces feeding motivation in rats.
abstract: The thyrotropin-releasing hormone (TRH), an anorexigenic factor that reduces food intake in food-restricted animals, may be involved in motivation for food. Injected centrally, TRH impairs acquisition of food-rewarded behavior. Through the TRH-R1 receptors, TRH injected in the nucleus accumbens increases dopamine content-perhaps the mechanism by which the peptide modulates food motivation. This, however, is still to be demonstrated. We sought to evaluate dopamine release by microdialysis after a TRH injection into the nucleus accumbens shell in free-moving fasted rats. In addition, we assessed dopamine content and turnover by HPLC and the relationship with the motivation for food by analyzing the performance of rats during a progressive-ratio (PR) operant-conditioning test. Finally, we determined serum leptin and triiodothyronine (T3) levels in order to evaluate the animals' metabolic response to food restriction and the impact of intra-accumbal TRH administration on circulating hormones. Intra-accumbal injections of TRH reduced food intake in food-restricted rats-compared to counterparts treated with saline-, without further decreasing T3 or leptin levels, which dropped due to their dietary regime. TRH-injected rats had lower breaking points on the PR schedule, which indicated lower motivation to eat. Accordingly, compared to saline-treated animals, dopamine release and turnover increased in the nucleus accumbens of TRH-injected rats, a finding that suggests a relationship between motivation for food and TRH-induced release of dopamine.
authors.affiliation: Molecular Neurophysiology Lab., Neuroscience Research, National Institute of Psychiatry, Ramón de la Fuente Muñiz, Mexico.
authors.forename: L
authors.initials: L
authors.lastname: Puga
authors.affiliation: Molecular Neurophysiology Lab., Neuroscience Research, National Institute of Psychiatry, Ramón de la Fuente Muñiz, Mexico.
authors.forename: V
authors.initials: V
authors.lastname: Alcántara-Alonso
authors.affiliation: Neurophysiology of Perception Lab., Neuroscience Research, National Institute of Psychiatry, Ramón de la Fuente Muñiz, Mexico.
authors.forename: U
authors.initials: U
authors.lastname: Coffeen
authors.affiliation: Neurophysiology of Perception Lab., Neuroscience Research, National Institute of Psychiatry, Ramón de la Fuente Muñiz, Mexico.
authors.forename: O
authors.initials: O
authors.lastname: Jaimes
authors.affiliation: Molecular Neurophysiology Lab., Neuroscience Research, National Institute of Psychiatry, Ramón de la Fuente Muñiz, Mexico. Electronic address: gortari@imp.edu.mx.
authors.forename: P
authors.initials: P
authors.lastname: de Gortari
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D004298:Dopamine / Q000378:metabolism*; D004435:Eating / Q000187:drug effects*; D005508:Food Deprivation; D020738:Leptin / Q000097:blood; D008297:Male; D017551:Microdialysis; D009042:Motivation / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012201:Reward; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*; D014284:Triiodothyronine / Q000097:blood
chemical_list: D020738:Leptin; D014284:Triiodothyronine; D015102:3,4-Dihydroxyphenylacetic Acid; D013973:Thyrotropin-Releasing Hormone; D004298:Dopamine
keywords: Dopamine; Microdialysis; Motivation; TRH