Differential effects of amphetamines-induced neurotoxicity on appetitive and aversive Pavlovian conditioning in mice

Neuropsychopharmacology. 2005 Jun;30(6):1128-37. doi: 10.1038/sj.npp.1300675.

Abstract

The abuse of substituted amphetamines such as methamphetamine (METH) and 3,4-methylenedioxymethamphetamine (MDMA/Ecstasy) can result in neurotoxicity, manifested as the depletion of dopamine (DA) and 5-hydroxytriptamine (5-HT; serotonin) axon terminal markers in humans and animal models. Human METH and MDMA users exhibit impairments in memory and executive functions, which may be a direct consequence of the neurotoxic potential of amphetamines. The objective of this study was to investigate the influence of amphetamines-induced neurotoxicity on Pavlovian learning. Using mouse models of selective DA neurotoxicity (METH; 5 mg/kg x 3), selective 5-HT neurotoxicity (fenfluramine /FEN; 25 mg/kg x 4) and dual DA and 5-HT neurotoxicity (MDMA; 15 mg/kg x 4), appetitive and aversive conditioning were investigated. Dopaminergic neurotoxicity significantly impaired METH and cocaine conditioned place preference (CPP), but had no effect on LiCl-induced conditioned place aversion (CPA). In contrast, serotonergic neurotoxicity significantly enhanced CPP, and had no effect on CPA. Dual dopaminergic/serotonergic neurotoxicity had no apparent effect on CPP; however, CPA was significantly attenuated. Postmortem analysis revealed that significantly diminished levels of DA and 5-HT markers persisted in the striatum, frontal cortex, hippocampus, and amygdala. These findings suggest that amphetamines-induced dopaminergic and serotonergic neurotoxicity exert opposing influences on the affective state produced by subsequent drug reward, while dual dopaminergic/serotonergic neurotoxicity impairs associative learning of aversive conditioning. Furthermore, results revealed that amphetamines-induced DA and 5-HT neurotoxicity modulates appetitive Pavlovian conditioning similar to other DA and 5-HT neurotoxins. Modulation of Pavlovian conditioning by amphetamines-induced neurotoxicity may be relevant to compulsive drug-seeking behavior in METH and MDMA abusers.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amphetamines / toxicity*
  • Animals
  • Antimanic Agents / pharmacology
  • Appetitive Behavior / drug effects*
  • Avoidance Learning / drug effects
  • Central Nervous System Stimulants / toxicity*
  • Conditioning, Classical / drug effects*
  • Dopamine / metabolism
  • Dopamine / physiology
  • Fenfluramine / toxicity
  • Hallucinogens / toxicity
  • Lithium Chloride
  • Male
  • Methamphetamine / toxicity
  • Mice
  • N-Methyl-3,4-methylenedioxyamphetamine / toxicity
  • Nerve Endings / drug effects
  • Neurotoxicity Syndromes / psychology*
  • Receptors, Serotonin / drug effects
  • Receptors, Serotonin / physiology
  • Reinforcement, Psychology
  • Reward
  • Serotonin / metabolism
  • Serotonin / physiology

Substances

  • Amphetamines
  • Antimanic Agents
  • Central Nervous System Stimulants
  • Hallucinogens
  • Receptors, Serotonin
  • Fenfluramine
  • Serotonin
  • Methamphetamine
  • Lithium Chloride
  • N-Methyl-3,4-methylenedioxyamphetamine
  • Dopamine