Cocaine increases dopamine release by mobilization of a synapsin-dependent reserve pool.
Cocaine primarily exerts its behavioral effects by enhancing dopaminergic neurotransmission, amplifying dopamine-encoded sensorimotor integration. The presumed mechanism for this effect is inhibition of the dopamine transporter, which blocks dopamine uptake and prolongs the duration of dopamine in the extracellular space. However, there is growing evidence that cocaine can also augment dopamine release. Here, we directly monitored the actions of cocaine on dopamine release by using electrochemical detection to measure extracellular dopamine in the striatum of anesthetized mice. Cocaine enhanced the levels of striatal dopamine produced by electrical stimulation of dopaminergic neurons. Even after pretreatment with alpha-methyl-p-tyrosine, which depletes the readily releasable pool of dopamine, cocaine was still capable of elevating dopamine levels. This suggests that cocaine enhances dopamine release by mobilizing a reserve pool of dopamine-containing synaptic vesicles. To test this hypothesis, we examined electrically evoked dopamine release in synapsin I/II/III triple knock-out mice, which have impaired synaptic vesicle reserve pools. Knock-out of synapsins greatly reduced the ability of cocaine to enhance dopamine release with long stimulus trains or after depletion of the newly synthesized pool. We therefore conclude that cocaine enhances dopamine release and does so by mobilizing a synapsin-dependent reserve pool of dopamine-containing synaptic vesicles. This capacity to enhance exocytotic release of dopamine may be important for the psychostimulant actions of cocaine.
Department of Chemistry, Neuroscience Center, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
B Jill
BJ
Venton
Andrew T
AT
Seipel
Paul E M
PE
Phillips
William C
WC
Wetsel
Daniel
D
Gitler
Paul
P
Greengard
George J
GJ
Augustine
R Mark
RM
Wightman
D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D003042:Cocaine / Q000494:pharmacology*; D019970:Cocaine-Related Disorders / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D004298:Dopamine / Q000378:metabolism*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008474:Medial Forebrain Bundle / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D017072:Neostriatum / Q000187:drug effects / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects* / Q000378:metabolism; D012201:Reward; D016704:Synapsins / Q000235:genetics*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D017557:Ventral Tegmental Area / Q000187:drug effects / Q000378:metabolism; D019805:alpha-Methyltyrosine / Q000494:pharmacology
D018765:Dopamine Uptake Inhibitors; D004791:Enzyme Inhibitors; D016704:Synapsins; D019805:alpha-Methyltyrosine; D003042:Cocaine; D004298:Dopamine