Fractionating impulsivity: contrasting effects of central 5-HT depletion on different measures of impulsive behavior

Neuropsychopharmacology. 2004 Jul;29(7):1331-43. doi: 10.1038/sj.npp.1300434.

Abstract

Reducing levels of 5-HT in the central nervous system has been associated with increases in impulsive behavior. However, the impulsivity construct describes a wide range of behaviors, including the inability to withhold a response, intolerance to delay of reward and perseveration of a nonrewarded response. Although these behaviors are generally studied using instrumental paradigms, impulsivity may also be reflected in simple Pavlovian tasks such as autoshaping and conditioned activity. This experiment aimed to characterize further the effects of central 5-HT depletion and to investigate whether different behavioral measures of impulsivity are inter-related, thus validating the construct. Rats received intracerebroventricular (ICV) infusions of vehicle (n=10) or the serotonergic neurotoxin 5,7-dihydroxytryptamine (n=12) which depleted forebrain 5-HT levels by about 90%. Lesioned animals showed significant increases in the speed and number of responses made in autoshaping, increased premature responding on a simple visual attentional task, enhanced expression of locomotor activity conditioned to food presentation, yet no change in impulsive choice was observed, as measured by a delay-discounting paradigm. Significant positive correlations were found between responses made in autoshaping and the level of conditioned activity, indicating a possible common basis for these behaviors, yet no correlations were found between other behavioral measures. These data strengthen and extend the hypothesis that 5-HT depletion increases certain types of impulsive responding. However, not all measures of impulsivity appear to be uniformly affected by 5-HT depletion, or correlate with each other, supporting the suggestion that impulsivity is not a unitary construct.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5,7-Dihydroxytryptamine / toxicity
  • Analysis of Variance
  • Animals
  • Attention / drug effects
  • Behavior, Animal
  • Biogenic Monoamines / analysis
  • Brain Chemistry
  • Central Nervous System / anatomy & histology
  • Central Nervous System / drug effects
  • Central Nervous System / metabolism*
  • Choice Behavior / drug effects
  • Conditioning, Classical / drug effects
  • Feeding Behavior / drug effects
  • Impulsive Behavior / diagnosis*
  • Impulsive Behavior / metabolism*
  • Injections, Intraventricular / methods
  • Male
  • Motor Activity / drug effects
  • Psychomotor Performance / drug effects
  • Rats
  • Reaction Time / drug effects
  • Reproducibility of Results
  • Serotonin / deficiency*
  • Serotonin / metabolism
  • Serotonin Agents / toxicity
  • Statistics, Nonparametric
  • Weights and Measures

Substances

  • Biogenic Monoamines
  • Serotonin Agents
  • 5,7-Dihydroxytryptamine
  • Serotonin