Comparative immunohistochemical distributions of carboxy terminus epitopes from the mu-opioid receptor splice variants MOR-1D, MOR-1 and MOR-1C in the mouse and rat CNS
Section snippets
Experimental procedures
All animal studies were reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) of the MSKCC and conform to NIH guidelines on the ethical use of animals. Care was taken to minimize the number of animals used and to minimize any suffering.
Transfected cells
The MOR-1D antiserum intensely labeled HEK-293 cells transiently transfected with a cDNA encoding MOR-1D (Fig. 2A), but not cells transfected with MOR-1 (Fig. 2H). No MOR-1D-LI was detected in non-transfected cells (Fig. 2F). Immunolabeling was abolished when the incubation was performed with either preimmune serum (Fig. 2E) or with immune serum preabsorbed with the peptide antigen (10 nM; Fig. 2C) or when the primary antibody was omitted (Fig. 2D). As a control, we also transfected HEK-293
Discussion
Splice variants of MOR-1 have unique distributions in the CNS. Previous studies looking at MOR-1B-LI observed a dense, but limited, presence in the olfactory bulb.52 MOR-1C-LI is particularly abundant in the lateral septum, the hypothalamic nuclei and the spinal cord. In the present study, the distribution of MOR-1D-LI was mainly restricted to the hippocampal formation, the nucleus of the solitary tract and the spinal cord. Within these regions, each splice variant has a unique pattern of
Conclusion
These immunohistochemical results demonstrate a differential localization of the splice variants of the MOR-1 gene in the CNS, consistent with the various physiological and pharmacological functions mediated by the opioid receptors. The recent identification of five novel exons within the MOR-1 gene and four new splice variants40., 41. illustrates the complexity of the MOR family. With the two variants reported several years ago, there are now seven different MOR-1 variants differing only in
Acknowledgements
This work was supported, in part, by a Mentored Scientist Award (DA00296) to Y.-X.P., research grants (DA02615 and DA06241) and a Senior Scientist Award (DA00220) to G.W.P. from the National Institute on Drug Abuse, as well as a core grant from the National Cancer Institute to the MSKCC (CA08748) and a research grant (HL18974) to the Laboratory of Neurobiology at CUMC.
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