ABSTRACT
Environmentalexperienceshaveanimportanteffecton thesensitivityofanindividualtodrugsofabuse.Studies ofdrugself-administrationinlaboratoryanimalshave shownthatbothphysicalandpsychologicalstressors facilitatetheacquisitionofdrugself-administration, probablybyincreasingthereinforcingefficacyofdrugs ofabuse.Stressorsalsofacilitatethereinstatementof drugtakingevenafterprolongedperiodsofwithdrawal. Theadrenalhormones,glucocorticoids,whichincrease thesensitivityofmesencephalicdopaminergicneurones todrugs,seemtobeoneofthebiologicalsubstratesof theeffectsofstressonthepropensitytodevelopdrug intake.Inthisreview,PierVincenzoPiazzaandMichel LeMoaldiscusstheoriesofdrugabuse,theinfluenceof differentstressfulexperiencesondrugself· administrationandtheirpossiblemechanismsofaction.
Itiswellknownthat,althoughalargenumberofpeople experimentwithdrugsforvariableperiodsoftime,only fewofthemdeveloparealaddiction,i.e.acompulsive drugusethatbecomesthemaingoal-directedactivityof thesubject'.Twoprincipaltheoreticalframeshavebeen usedtoexplainthetransitionfromdrugusetoaddiction. Theycanbedefinedasadrug·andanindividual· centeredvisionofaddiction,respectively.
