Restriction of dietary protein in rats increases progressive-ratio motivation for protein

Giulia Chiacchierini* (Corresponding Author), Fabien Naneix, John Apergis-Schoute, James E. McCutcheon

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Low-protein diets can impact food intake and appetite, but it is not known if motivation for food is changed. In the present study, we used an operant behavioral task – the progressive ratio test – to assess whether motivation for different foods was affected when rats were maintained on a protein-restricted diet (REST, 5% protein diet) compared to non-restricted control rats (CON, 18% protein). Rats were tested either with nutritionally-balanced pellets (18.7% protein, Experiment 1) or protein-rich pellets (35% protein, Experiment 2) as reinforcers. Protein restriction increased breakpoint for protein-rich pellets, relative to CON rats, whereas no difference in breakpoint for nutritionally-balanced pellets was observed between groups. When given free access to either nutritionally-balanced pellets or protein-rich pellets, REST and CON rats did not differ in their intake. We also tested whether a previous history of protein restriction might affect present motivation for different types of food, by assessing breakpoint of previously REST animals that were subsequently put on standard maintenance chow (protein-repleted rats, REPL, Experiment 2). REPL rats did not show increased breakpoint, relative to their initial encounter with protein-rich pellets while they were protein-restricted. This study demonstrates that restriction of dietary protein induces a selective increased motivation for protein-rich food, a behavior that disappears once rats are not in need of protein.
Original languageEnglish
Article number113877
JournalPhysiology and Behavior
Volume254
Early online date29 Jun 2022
DOIs
Publication statusPublished - 1 Oct 2022

Keywords

  • amino acids
  • protein
  • diet
  • motivation
  • progressive ratio
  • rat

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