title: Mouse strain differences in locomotor, sensitisation and rewarding effect of heroin; association with alterations in MOP-r activation and dopamine transporter binding.
abstract: There is growing agreement that genetic factors play an important role in the risk to develop heroin addiction, and comparisons of heroin addiction vulnerability in inbred strains of mice could provide useful information on the question of individual vulnerability to heroin addiction. This study examined the rewarding and locomotor-stimulating effects of heroin in male C57BL/6J and DBA/2J mice. Heroin induced locomotion and sensitisation in C57BL/6J but not in DBA/2J mice. C57BL/6J mice developed conditioned place preference (CPP) to the highest doses of heroin, while DBA/2J showed CPP to only the lowest heroin doses, indicating a higher sensitivity of DBA/2J mice to the rewarding properties of heroin vs C57BL/6J mice. In order to investigate the neurobiological substrate underlying some of these differences, the effect of chronic 'intermittent' escalating dose heroin administration on the opioid, dopaminergic and stress systems was explored. Twofold higher mu-opioid receptor (MOP-r)-stimulated [35S]GTPgammaS binding was observed in the nucleus accumbens and caudate of saline-treated C57BL/6J mice compared with DBA/2J. Heroin decreased MOP-r density in brain regions of C57BL/6J mice, but not in DBA/2J. A higher density of dopamine transporters (DAT) was observed in nucleus accumbens shell and caudate of heroin-treated DBA/2J mice compared with heroin-treated C57BL/6J. There were no effects on D1 and D2 binding. Chronic heroin administration decreased corticosterone levels in both strains with no effect of strain. These results suggest that genetic differences in MOP-r activation and DAT expression may be responsible for individual differences in vulnerability to heroin addiction.
authors.affiliation: Faculty of Health and Medical Sciences, AY Building, University of Surrey, Guildford, Surrey GU2 7XH, UK. a.bailey@surrey.ac.uk
authors.forename: Alexis
authors.initials: A
authors.lastname: Bailey
authors.forename: Athanasios
authors.initials: A
authors.lastname: Metaxas
authors.forename: Ream
authors.initials: R
authors.lastname: Al-Hasani
authors.forename: Helen L
authors.initials: HL
authors.lastname: Keyworth
authors.forename: Duncan M
authors.initials: DM
authors.lastname: Forster
authors.forename: Ian
authors.initials: I
authors.lastname: Kitchen
mesh_terms: D000818:Animals; D002421:Caudate Nucleus / Q000187:drug effects / Q000378:metabolism; D003216:Conditioning, Operant / Q000187:drug effects; D003345:Corticosterone / Q000097:blood; D050483:Dopamine Plasma Membrane Transport Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D003932:Heroin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009043:Motor Activity / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D011954:Receptors, Dopamine / Q000378:metabolism; D017450:Receptors, Opioid, mu / Q000378:metabolism*; D012201:Reward; D013045:Species Specificity
chemical_list: D050483:Dopamine Plasma Membrane Transport Proteins; D011954:Receptors, Dopamine; D017450:Receptors, Opioid, mu; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D003932:Heroin; D003345:Corticosterone