Delta opioid receptor mRNA expression is changed in the thalamus and brainstem of monoarthritic rats.
Changes in the mRNA expression of neurotransmitters receptors under chronic pain conditions have been described in various areas of the central nervous system (CNS). Delta opioid receptors (DORs) have been implicated in pain mechanisms but, although its mRNA expression has been studied in the rat CNS, there are no reports describing its distribution in specific thalamic and brainstem nuclei during chronic inflammatory pain. Here, in situ hybridization for DOR mRNA was performed in brain sections from control and monoarthritic (MA) rats with 2, 4, 7 and 14 days of inflammation. Grain densities were determined bilaterally in the ventrobasal complex (VB), posterior (Po), centromedial/centrolateral (CM/CL) and reticular (Rt) nuclei of the thalamus, and in the dorsal reticular (DRt), lateral reticular (LRt) and parvocellular reticular (PCRt) nuclei of the brainstem. Control animals exhibited weak mRNA expression in the VB, Po and CM/CL, as well as in PCRt, while moderate grain densities were observed in the Rt, DRt and LRt. During MA, DOR mRNA expression was significantly decreased (22%) in the Rt contralateral to the affected joint at both 7 and 14 days of inflammation, as compared to controls. A bilateral reduction (35%) was also observed in the DRt at 14 days of MA, while a contralateral increase was found in the PCRt at 7 days (+39%). No significant changes were observed in the other regions analyzed. Thus, data show changes in the DOR mRNA expression during the development of chronic inflammatory pain, in thalamic and brainstem nuclei implicated in pain processing mechanisms.
Institute of Histology and Embryology, Faculty of Medicine of Porto and IBMC, University of Porto, Portugal. fanineto@med.up.pt
Fani Lourença
FL
Neto
Ana Raquel
AR
Carvalhosa
Joana
J
Ferreira-Gomes
Carlos
C
Reguenga
José Manuel
JM
Castro-Lopes
D000818:Animals; D001168:Arthritis / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D001931:Brain Mapping; D001933:Brain Stem / Q000378:metabolism* / Q000503:physiopathology; D002908:Chronic Disease; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000235:genetics; D007839:Functional Laterality / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D017403:In Situ Hybridization; D008297:Male; D009434:Neural Pathways / Q000378:metabolism / Q000503:physiopathology; D018847:Opioid Peptides / Q000378:metabolism*; D010148:Intractable Pain / Q000503:physiopathology; D020656:Posterior Thalamic Nuclei / Q000378:metabolism / Q000503:physiopathology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000235:genetics*; D012154:Reticular Formation / Q000378:metabolism / Q000503:physiopathology; D013788:Thalamus / Q000378:metabolism* / Q000503:physiopathology; D020651:Ventral Thalamic Nuclei / Q000378:metabolism / Q000503:physiopathology
D018847:Opioid Peptides; D012333:RNA, Messenger; D017465:Receptors, Opioid, delta