In vivo dopaminergic and behavioral responses to acute cocaine are altered in adenosine A(2A)  receptor knockout mice.
Adenosine, acting on adenosine A(2A) receptors (A2ARs), regulates addictive processes induced by drugs of abuse. This study investigates the role of A(2A) adenosine receptors in neurochemical and behavioral responses to an acute cocaine challenge. Changes in the extracellular levels of dopamine (DA) in the nucleus accumbens (NAc) of mice lacking A(2A) adenosine receptors and wild type (WT) littermates after an acute cocaine (20 mg/kg) administration were evaluated by in vivo microdialysis studies. Locomotor effects induced by cocaine were measured during the microdialysis procedure. Cocaine-evoked increases in extracellular DA were not sustained in mice lacking A(2A) Rs in comparison with wild-type mice (P < 0.05). Cocaine administration significantly increased ambulatory activity in both genotypes. However, overall locomotor activity was further increased, whereas rest and small local movement measures were significantly attenuated in the A(2A) R knockout mice compared with WT littermates (P < 0.05). Our findings support an important role for adenosine A(2A) R in modulating the acute effects of cocaine, as demonstrated by the decrease in cocaine-evoked dopaminergic transmission in the NAc. Furthermore, the results support an important antagonistic role of A(2A) R in vivo in regulating psychostimulant-induced hyperlocomotion.
Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom. lisa.wells@imanova.co.uk
Lisa
L
Wells
Jolanta
J
Opacka-Juffry
Donald
D
Fisher
Catherine
C
Ledent
Susanna
S
Hourani
Ian
I
Kitchen
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003042:Cocaine / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D017551:Microdialysis; D009043:Motor Activity / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000187:drug effects*; D043705:Receptor, Adenosine A2A / Q000235:genetics* / Q000502:physiology
D018765:Dopamine Uptake Inhibitors; D043705:Receptor, Adenosine A2A; D003042:Cocaine; D004298:Dopamine