title: Role of aberrant striatal dopamine D1 receptor/cAMP/protein kinase A/DARPP32 signaling in the paradoxical calming effect of amphetamine.
abstract: Attention deficit/hyperactivity disorder (ADHD) is characterized by inattention, impulsivity, and motor hyperactivity. Several lines of research support a crucial role for the dopamine transporter (DAT) gene in this psychiatric disease. Consistently, the most commonly prescribed medications in ADHD treatment are stimulant drugs, known to preferentially act on DAT. Recently, a knock-in mouse [DAT-cocaine insensitive (DAT-CI)] has been generated carrying a cocaine-insensitive DAT that is functional but with reduced dopamine uptake function. DAT-CI mutants display enhanced striatal extracellular dopamine levels and basal motor hyperactivity. Herein, we showed that DAT-CI animals present higher striatal dopamine turnover, altered basal phosphorylation state of dopamine and cAMP-regulated phosphoprotein 32 kDa (DARPP32) at Thr75 residue, but preserved D(2) receptor (D(2)R) function. However, although we demonstrated that striatal D(1) receptor (D(1)R) is physiologically responsive under basal conditions, its stimulus-induced activation strikingly resulted in paradoxical electrophysiological, behavioral, and biochemical responses. Indeed, in DAT-CI animals, (1) striatal LTP was completely disrupted, (2) R-(+)-6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF 81297) treatment induced paradoxical motor calming effects, and (3) SKF 81297 administration failed to increase cAMP/protein kinase A (PKA)/DARPP32 signaling. Such biochemical alteration selectively affected dopamine D(1)Rs since haloperidol, by blocking the tonic inhibition of D(2)R, unmasked a normal activation of striatal adenosine A(2A) receptor-mediated cAMP/PKA/DARPP32 cascade in mutants. Most importantly, our studies highlighted that amphetamine, nomifensine, and bupropion, through increased striatal dopaminergic transmission, are able to revert motor hyperactivity of DAT-CI animals. Overall, our results suggest that the paradoxical motor calming effect induced by these drugs in DAT-CI mutants depends on selective aberrant phasic activation of D(1)R/cAMP/PKA/DARPP32 signaling in response to increased striatal extracellular dopamine levels.
authors: Centro Ingegneria Genetica Biotecnologie Avanzate, 80131 Naples, Italy.
authors: Francesco
authors: F
authors: Napolitano
authors: Alessandra
authors: A
authors: Bonito-Oliva
authors: Mauro
authors: M
authors: Federici
authors: Manolo
authors: M
authors: Carta
authors: Francesco
authors: F
authors: Errico
authors: Salvatore
authors: S
authors: Magara
authors: Giuseppina
authors: G
authors: Martella
authors: Robert
authors: R
authors: Nisticò
authors: Diego
authors: D
authors: Centonze
authors: Antonio
authors: A
authors: Pisani
authors: Howard H
authors: HH
authors: Gu
authors: Nicola B
authors: NB
authors: Mercuri
authors: Alessandro
authors: A
authors: Usiello
mesh_terms: D000661:Amphetamine / Q000494:pharmacology*; D000818:Animals; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003342:Corpus Striatum / Q000187:drug effects* / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004192:Discrimination, Psychological / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000378:metabolism; D050483:Dopamine Plasma Membrane Transport Proteins / Q000235:genetics; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32 / Q000378:metabolism; D055879:Gene Knock-In Techniques; D017774:Long-Term Potentiation / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009043:Motor Activity / Q000187:drug effects* / Q000502:physiology; D009154:Mutation; D011897:Random Allocation; D017447:Receptors, Dopamine D1 / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000697:Central Nervous System Stimulants; D050483:Dopamine Plasma Membrane Transport Proteins; D051937:Dopamine and cAMP-Regulated Phosphoprotein 32; C497929:Ppp1r1b protein, mouse; D017447:Receptors, Dopamine D1; D017448:Receptors, Dopamine D2; D000661:Amphetamine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D004298:Dopamine