title: Repeated amphetamine administration in rats revealed consistency across days and a complete dissociation between locomotor and hypothalamic-pituitary-adrenal axis effects of the drug.
abstract: BACKGROUND
  Most drugs of abuse stimulate both locomotor activity and the hypothalamic-pituitary-adrenal (HPA) axis, but the relationship between the two responses within the same subjects and their reliabilities has been scarcely studied. Our objectives were to study: (1) the consistency and stability across time of locomotor and HPA activation induced by repeated d-amphetamine (AMPH); (2) the relationship between locomotor and hormonal responses to AMPH; and (3) the relationship between novelty-induced activity and both types of responses to the drug.
  
  
  METHODS
  Male adult rats were exposed to a novel environment to study the locomotor response. Later, they were injected with AMPH (2 mg/kg, sc) for 5 days. In Experiment 1, Plasma adrenocorticotropin (ACTH) and corticosterone levels in response to AMPH were studied on days 1, 3, and 5, and locomotor response on days 2 and 4. In Experiment 2, ACTH and corticosterone responses were studied on days 2 and 4, and locomotor response on days 1, 3, and 5.
  
  
  RESULTS
  Across days, both locomotor and HPA responses to the drug were consistent, but independent measures, unrelated to the reactivity to novelty. As measured by the area under the curve, the HPA response to AMPH desensitized with the repeated injection, whereas the initial locomotor response to the drug increased.
  
  
  CONCLUSIONS
  Dissociation exists between HPA and locomotor activation induced by AMPH, which seemed to be both reliable individual traits. Locomotor reactivity to novelty was related neither to HPA nor to locomotor responses to AMPH.
authors.affiliation: Institute of Neurosciences, Autonomous University of Barcelona, Bellaterra, Barcelona, Spain.
authors.forename: Humberto
authors.initials: H
authors.lastname: Gagliano
authors.forename: Raül
authors.initials: R
authors.lastname: Andero
authors.forename: Antonio
authors.initials: A
authors.lastname: Armario
authors.forename: Roser
authors.initials: R
authors.lastname: Nadal
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D019540:Area Under Curve; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D003345:Corticosterone / Q000097:blood; D003913:Dextroamphetamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004777:Environment; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D007279:Injections, Subcutaneous; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013045:Species Specificity
chemical_list: D000697:Central Nervous System Stimulants; D000324:Adrenocorticotropic Hormone; D003913:Dextroamphetamine; D003345:Corticosterone