Compromised decision-making and increased gambling proneness following dietary serotonin depletion in rats

Neuropharmacology. 2012 Mar;62(4):1640-50. doi: 10.1016/j.neuropharm.2011.11.002. Epub 2011 Nov 16.


Psycho-genetic studies have revealed a role for the brain serotonin system in gambling proneness and poor decision-making. We assessed whether manipulation of brain serotonin levels in rats affected performance in operant-based tasks for decision-making and gambling proneness. Male Wistar rats were exposed to an l-tryptophan (TRP) deficient diet (0.0 g/kg; T- group) or to a control, l-tryptophan containing diet (2.8 g/kg; T+ group). The same rats were tested for decision-making performance in the rodent Iowa Gambling Task (rIGT) using home-cage operant panels, and subsequently for gambling proneness in a Probabilistic Delivery Task (rPDT) using classic Skinnerboxes. At sacrifice, monoamines and metabolites were evaluated with HPLC analysis, confirming a drastically reduced serotonin synthesis, as well as altered dopamine turnover in the prefrontal cortex of T- rats. As expected, control rats (T+) progressively chose the option with the best long-term payoff in the rIGT, and also shifted from "Large & Luck-Linked" (LLL) to "Small & Sure" (SS) reinforcers in the rPDT. In contrast, depleted animals (T-) exhibited a weaker improvement of performance in the rIGT and maintained a sub-optimal attraction for LLL reinforcer in the rPDT. Comparing individual performances in both tests, we found a significant correlation between the two tasks in control (T+) but not in depleted (T-) rats. The present study revealed that (1) brain 5-HT depletion leads to poor decision-making and to gambling proneness; (2) the relationship between these two traits, shown in the control group, was disrupted in 5-HT depleted rats. The data are discussed in terms of changes within forebrain loops involved in cognitive and motivational/affective processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Decision Making / physiology*
  • Diet*
  • Dopamine / metabolism
  • Gambling / metabolism*
  • Gambling / physiopathology
  • Male
  • Motivation
  • Prefrontal Cortex / metabolism*
  • Rats
  • Rats, Wistar
  • Serotonin / metabolism*
  • Tryptophan / deficiency*


  • Serotonin
  • Tryptophan
  • Dopamine