Dopamine D2 Receptors in the Paraventricular Thalamus Attenuate Cocaine Locomotor Sensitization

• Published in: eNeuro 2017-09, Vol.4 (5), p.ENEURO.0227-17.2017
• Main Authors: Clark, Abigail M, Leroy, Felix, Martyniuk, Kelly M, Feng, Wendy, McManus, Erika, Bailey, Matthew R, Javitch, Jonathan A, Balsam, Peter D, Kellendonk, Christoph
• Format: Article
• Language: English
• Subjects: Animals; Cocaine - pharmacology; Dopamine Agonists - pharmacology; Dopamine Antagonists - pharmacology; Dopamine Uptake Inhibitors - pharmacology; Dose-Response Relationship, Drug; Fear - drug effects; Female; Locomotion - drug effects; Locomotion - genetics; Male; Maze Learning - drug effects; Membrane Potentials - drug effects; Membrane Potentials - genetics; Mice; Mice, Inbred C57BL; Mice, Transgenic; Midline Thalamic Nuclei - drug effects; New Research; Quinpirole - pharmacology; Receptors, Dopamine D2 - genetics; Receptors, Dopamine D2 - metabolism; Sulpiride - pharmacology; Transduction, Genetic
• ISSN: 2373-2822; 2373-2822
• DOI: 10.1523/eneuro.0227-17.2017

Alterations in thalamic dopamine (DA) or DA D2 receptors (D2Rs) have been measured in drug addiction and schizophrenia, but the relevance of thalamic D2Rs for behavior is largely unknown. Using hybridization and mice expressing green fluorescent protein (GFP) under the promoter, we found that D2R expression within the thalamus is enriched in the paraventricular nucleus (PVT) as well as in more ventral midline thalamic nuclei. Within the PVT, D2Rs are inhibitory as their activation inhibits neuronal action potentials in brain slices. Using Cre-dependent anterograde and retrograde viral tracers, we further determined that PVT neurons are reciprocally interconnected with multiple areas of the limbic system including the amygdala and the nucleus accumbens (NAc). Based on these anatomical findings, we analyzed the role of D2Rs in the PVT in behaviors that are supported by these areas and that also have relevance for schizophrenia and drug addiction. Male and female mice with selective overexpression of D2Rs in the PVT showed attenuated cocaine locomotor sensitization, whereas anxiety levels, fear conditioning, sensorimotor gating, and food-motivated behaviors were not affected. These findings suggest the importance of PVT inhibition by D2Rs in modulating the sensitivity to cocaine, a finding that may have novel implications for human drug use.