Gamma-Aminobutyric Acidergic Projections From the Dorsal Raphe to the Nucleus Accumbens Are Regulated by Neuromedin U.
Neuromedin U (NMU) is a neuropeptide enriched in the nucleus accumbens shell (NAcSh), a brain region associated with reward. While NMU and its receptor, NMU receptor 2 (NMUR2), have been studied for the ability to regulate food reward, NMU has not been studied in the context of drugs of abuse (e.g., cocaine). Furthermore, the neuroanatomical pathways that express NMUR2 and its ultrastructural localization are unknown.



Immunohistochemistry was used to determine the synaptic localization of NMUR2 in the NAcSh and characterize which neurons express this receptor (n = 17). The functional outcome of NMU on NMUR2 was examined using microdialysis (n = 16). The behavioral effects of NMU microinjection directly to the NAcSh were investigated using cocaine-evoked locomotion (n = 93). The specific effects of NMUR2 knockdown on cocaine-evoked locomotion were evaluated using viral-mediated RNA interference (n = 40).



NMUR2 is localized to presynaptic gamma-aminobutyric acidergic nerve terminals in the NAcSh originating from the dorsal raphe nucleus. Furthermore, NMU microinjection to the NAcSh decreased local gamma-aminobutyric acid concentrations. Next, we evaluated the effects of NMU microinjection on behavioral sensitization to cocaine. When repeatedly administered throughout the sensitization regimen, NMU attenuated cocaine-evoked hyperactivity. Additionally, small hairpin RNA-mediated knockdown of presynaptic NMUR2 in the NAcSh using a retrograde viral vector potentiated cocaine sensitization.



Together, these data reveal that NMUR2 modulates a novel gamma-aminobutyric acidergic pathway from the dorsal raphe nucleus to the NAcSh to influence behavioral responses to cocaine.
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
James M
JM
Kasper
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
David L
DL
McCue
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
Adrianna J
AJ
Milton
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
Angelia
A
Szwed
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
Catherine M
CM
Sampson
Department of Psychiatry and Behavioral Sciences, Northwestern Feinberg School of Medicine, Chicago, Illinois.
Mei
M
Huang
Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas.
Susan
S
Carlton
Department of Psychiatry and Behavioral Sciences, Northwestern Feinberg School of Medicine, Chicago, Illinois.
Herbert Y
HY
Meltzer
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas.
Kathryn A
KA
Cunningham
Center for Addiction Research, Department of Pharmacology & Toxicology, University of Texas Medical Branch, Galveston, Texas. Electronic address: jdhommel@utmb.edu.
Jonathan D
JD
Hommel
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D003042:Cocaine / Q000494:pharmacology*; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology*; D065847:Dorsal Raphe Nucleus / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D009714:Nucleus Accumbens / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017981:Receptors, Neurotransmitter / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D018765:Dopamine Uptake Inhibitors; D009479:Neuropeptides; D017981:Receptors, Neurotransmitter; C082444:neuromedin U receptor; C056900:neuromedin U; D005680:gamma-Aminobutyric Acid; D003042:Cocaine
AAV6; Cocaine; GABA; Neuropeptide; Nonserotonergic; RNAi