title: Extrasynaptic targeting of NMDA receptors following D1 dopamine receptor activation and cocaine self-administration.
abstract: We previously showed that after repeated exposure to cocaine, D1-like dopamine receptor (D1DR) stimulation reverses plastic changes of AMPA receptor-mediated signaling in the nucleus accumbens shell. However, there is little information on the impact of cocaine self-administration on D1-NMDA receptor interactions in this brain region. Here, using whole-cell patch-clamp recordings, we assessed whether cocaine self-administration alters the effects of D1DR stimulation on synaptic and extrasynaptic NMDA receptors (NMDARs). In slices from cocaine-naive rats, pretreatment with a D1DR agonist decreased synaptic NMDAR-mediated currents and increased the contribution of extrasynaptic NMDARs. In contrast, neither cocaine self-administration alone nor cocaine experience followed by D1DR stimulation had an effect on synaptic or extrasynaptic NMDAR signaling. Activation of extrasynaptic NMDARs relies on the availability of extracellular glutamate, which is regulated primarily by glutamate transporters. In cocaine-experienced animals, relative to cocaine-naive rats, administration of a glutamate reuptake blocker, DL-threo-β-benzyloxyaspartic acid, revealed increased extrasynaptic NMDAR activity and stronger baseline activity of glutamate uptake transporters. In cocaine-naive rats, the D1DR-mediated increase in extrasynaptic NMDAR signaling was independent of the activity of glutamate reuptake transporters. Together, these results indicate that cocaine experience blunts the influence of D1DRs on synaptic and extrasynaptic NMDAR signaling. Additionally, prior cocaine self-administration limits activation of the extrasynaptic NMDAR pool by increasing glutamate reuptake. These findings outline a pattern of adaptive interactions between D1DRs and NMDARs in the nucleus accumbens shell and demonstrate upregulation of extrasynaptic NMDAR signaling as a novel consequence of cocaine self-administration.
authors.affiliation: Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA. ortinski@mail.med.upenn.edu
authors.forename: Pavel I
authors.initials: PI
authors.lastname: Ortinski
authors.forename: Jill R
authors.initials: JR
authors.lastname: Turner
authors.forename: R Christopher
authors.initials: RC
authors.lastname: Pierce
mesh_terms: D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D027322:Amino Acid Transport System X-AG / Q000037:antagonists & inhibitors / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D015153:Blotting, Western; D003042:Cocaine / Q000494:pharmacology*; D019970:Cocaine-Related Disorders / Q000523:psychology*; D003627:Data Interpretation, Statistical; D018491:Dopamine Agonists / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D005110:Extracellular Space / Q000502:physiology; D018698:Glutamic Acid / Q000502:physiology; D008297:Male; D009714:Nucleus Accumbens / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000819:agonists*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*; D012646:Self Administration; D013569:Synapses / Q000502:physiology; D015854:Up-Regulation
chemical_list: D027322:Amino Acid Transport System X-AG; D018491:Dopamine Agonists; D018765:Dopamine Uptake Inhibitors; D017447:Receptors, Dopamine D1; D016194:Receptors, N-Methyl-D-Aspartate; C120673:benzyloxyaspartate; D001224:Aspartic Acid; D018698:Glutamic Acid; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D003042:Cocaine