title: Effect of orexin-B-saporin-induced lesions of the lateral hypothalamus on performance on a progressive ratio schedule.
abstract: It has been suggested that a sub-population of orexinergic neurones whose somata lie in the lateral hypothalamic area (LHA) play an important role in regulating the reinforcing value of both food and drugs. This experiment examined the effect of disruption of orexinergic mechanisms in the LHA on performance on the progressive ratio schedule of reinforcement, in which the response requirement increases progressively for successive reinforcers. The data were analysed using a mathematical model which yields a quantitative index of reinforcer value and dissociates effects of interventions on motor and motivational processes. Rats were trained under a progressive ratio schedule using food-pellet reinforcement. They received bilateral injections of conjugated orexin-B-saporin (OxSap) into the LHA or sham lesions. Training continued for a further 40 sessions after surgery. Equations were fitted to the response rate data from each rat, and the parameters of the model were derived for successive blocks of 10 sessions. The OxSap lesion reduced the number of orexin-containing neurones in the LHA by approximately 50% compared with the sham-lesioned group. The parameter expressing the incentive value of the reinforcer was not significantly altered by the lesion. However, the parameter related to the maximum response rate was significantly affected, suggesting that motor capacity was diminished in the OxSap-lesioned group. The results indicate that OxSap lesions of the LHA disrupted food-reinforced responding on the progressive ratio schedule. It is suggested that this disruption was brought about by a change in non-motivational (motor) processes.
authors.affiliation: Psychopharmacology Section, Division of Psychiatry, University of Nottingham, Nottingham, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Olarte-Sánchez
authors.forename: L
authors.initials: L
authors.lastname: Valencia Torres
authors.forename: S
authors.initials: S
authors.lastname: Body
authors.forename: H J
authors.initials: HJ
authors.lastname: Cassaday
authors.forename: C M
authors.initials: CM
authors.lastname: Bradshaw
authors.forename: E
authors.initials: E
authors.lastname: Szabadi
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001835:Body Weight / Q000187:drug effects; D003216:Conditioning, Operant / Q000187:drug effects; D004435:Eating / Q000187:drug effects; D005260:Female; D007026:Hypothalamic Area, Lateral / Q000187:drug effects*; D007031:Hypothalamus / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology*; D009042:Motivation / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D009474:Neurons / Q000187:drug effects; D009479:Neuropeptides / Q000494:pharmacology*; D000068797:Orexins; D058573:Performance-Enhancing Substances / Q000494:pharmacology*; D011597:Psychomotor Performance / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012054:Reinforcement, Psychology; D054789:Ribosome Inactivating Proteins, Type 1 / Q000494:pharmacology*; D000076985:Saporins
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D000068797:Orexins; D058573:Performance-Enhancing Substances; D054789:Ribosome Inactivating Proteins, Type 1; D000076985:Saporins