title: Influence of early postnatal rearing conditions on mesocorticolimbic dopamine and behavioural responses to psychostimulants and stressors in adult rats.
abstract: While many experiment with drugs, relatively few individuals develop a true addiction. We hypothesized that, in rats, such individual differences in the actions of addictive drugs might be determined by postnatal rearing conditions. To test this idea, we investigated whether stimulant- and stress-induced activation of nucleus accumbens dopamine transmission and dopamine-dependent behaviours might differ among adults rats that had been either repeatedly subjected to prolonged maternal separation or a brief handling procedure or left undisturbed (non-handled) during the first 14 days of life. We found that, in comparison with their handled counterparts, maternally separated and non-handled animals are hyperactive when placed in a novel setting, display a dose-dependent higher sensitivity to cocaine-induced locomotor activity and respond to a mild stressor (tail-pinch) with significantly greater increases in nucleus accumbens dopamine levels. In addition, maternally separated animals were found to sensitize to the locomotor stimulant action of amphetamine when repeatedly stressed under conditions that failed to sensitize handled and non-handled animals. Finally, quantitative receptor autoradiography revealed a lower density of nucleus accumbens-core and striatal dopamine transporter sites in maternally separated animals. Interestingly, we also found greatly reduced D(3) dopamine receptor binding and mRNA levels in the nucleus accumbens-shell of handled animals. Together, these findings provide compelling evidence that disruptions in early postnatal rearing conditions can lead to profound and lasting changes in the responsiveness of mesocorticolimbic dopamine neurons to stress and psychostimulants, and suggest a neurobiological basis for individual differences in vulnerability to compulsive drug taking.
authors.affiliation: Department of Psychology, University of California Santa Barbara, CA 93106, USA.
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Brake
authors.forename: Tie Yuan
authors.initials: TY
authors.lastname: Zhang
authors.forename: Josie
authors.initials: J
authors.lastname: Diorio
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Meaney
authors.forename: Alain
authors.initials: A
authors.lastname: Gratton
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001345:Autoradiography / Q000379:methods; D001522:Behavior, Animal / Q000187:drug effects; D001665:Binding Sites; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003042:Cocaine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000493:pharmacokinetics; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004563:Electrochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D008426:Maternal Deprivation; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000378:metabolism; D009043:Motor Activity / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009714:Nucleus Accumbens / Q000187:drug effects* / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D011954:Receptors, Dopamine / Q000378:metabolism; D013315:Stress, Psychological / Q000378:metabolism*; D013764:Tetrahydronaphthalenes / Q000493:pharmacokinetics; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D000697:Central Nervous System Stimulants; D018491:Dopamine Agonists; D050483:Dopamine Plasma Membrane Transport Proteins; D018765:Dopamine Uptake Inhibitors; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D011954:Receptors, Dopamine; D013764:Tetrahydronaphthalenes; D014316:Tritium; C021279:(1R-(exo,exo))-3-(4-fluorophenyl)-8-methyl-8- azabicyclo(3.2.1)octane-2-carboxylic acid, methyl ester; D000661:Amphetamine; D003042:Cocaine; C031349:7-hydroxy-2-N,N-dipropylaminotetralin; D004298:Dopamine