The selective serotonin reuptake inhibitor paroxetine decreases breakpoint of rats engaging in a progressive ratio licking task for sucrose and quinine solutions

Chem Senses. 2013 Mar;38(3):211-20. doi: 10.1093/chemse/bjs096. Epub 2012 Dec 19.


Increased serotonergic activity has been shown to reduce motivation to ingest, which may involve, in part, gustatory processes. Here, we examined the effect of paroxetine, a selective serotonin reuptake inhibitor, on appetitive responding for a preferred and an avoided taste solution using a progressive ratio (PR) task in which licking was employed as the operant. Male Sprague-Dawley rats (n = 8/taste stimulus) were trained to respond for a concentration series of sucrose or quinine on fixed and PR schedules of reinforcement. Performance for sucrose was assessed while the rats were partially food- and water-restricted and nondeprived, and performance for water and quinine was assessed while the rats were water-deprived. Then, the rats were injected with vehicle (10% dimethyl sulfoxide, 1mL/kg intraperitoneal [ip], -1h) or paroxetine (5mg/kg), and their responding on a PR schedule for sucrose measured when the rats were nondeprived or for water and quinine when the rats were water-deprived. Paroxetine decreased breakpoint, which was defined as the number of operant (e.g., dry) licks in the final reinforced ratio, for water, quinine, and sucrose. This demonstrates that a general systemic increase in serotonergic activity decreases the appetitive-based responses to both preferred and nonpreferred fluids under different deprivation states.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Appetitive Behavior / drug effects*
  • Food Deprivation
  • Male
  • Paroxetine / pharmacology*
  • Quinine / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Reinforcement, Psychology
  • Selective Serotonin Reuptake Inhibitors / pharmacology*
  • Sucrose / pharmacology*
  • Water Deprivation


  • Serotonin Uptake Inhibitors
  • Paroxetine
  • Sucrose
  • Quinine