Immunohistochemical study of the expression of exon11-containing mu opioid receptor variants in mouse brain

Neuroscience. 2004;127(2):419-30. doi: 10.1016/j.neuroscience.2004.03.033.


The cloned mu opioid receptor MOR-1 undergoes alternative splicing. Extensive 3'-splicing downstream from exon 3 leads to a number of C-terminal splice variants that are differentially expressed within the CNS. Recently, 5'-splicing has been observed with eight additional variants containing exon 11, a new exon located approximately 10 kb upstream from exon 1 that is under the control of a different promoter located even further upstream. Three of these variants generate the same protein as MOR-1 itself, but under the control of the new exon 11 promoter. Three variants in which exon 11 is translated have been identified within the brain, including MOR-1G, MOR-1M and MOR-1N. The present paper defines immunohistochemically the distribution of these variants using an exon 11-specific antiserum. The expression of exon 11-like immunoreactivity (-LI) was seen primarily in the olfactory tubercle, caudate-putamen, globus pallidus and substantia nigra. We did not observe exon 11-LI in a number of regions expressing MOR-1. Within the caudate-putamen, the general pattern of labeling was diffuse, in contrast to the pattern seen with an exon 4-generated antiserum that labels MOR-1 itself. However, we did observe in the caudate-putamen co-expression of exon 4- and exon 11-LI in cells that were apposed to dopaminergic terminals. These results provide new insights regarding the potential physiological significance of these exon 11-containing variants.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alternative Splicing / genetics*
  • Animals
  • Antibody Specificity
  • Brain / cytology
  • Brain / metabolism*
  • Cell Line
  • Corpus Striatum / cytology
  • Corpus Striatum / metabolism
  • Dopamine / metabolism
  • Exons / genetics*
  • Gene Expression Regulation / genetics
  • Humans
  • Immunohistochemistry
  • Male
  • Mice
  • Olfactory Pathways / cytology
  • Olfactory Pathways / metabolism
  • Presynaptic Terminals / metabolism
  • Presynaptic Terminals / ultrastructure
  • Promoter Regions, Genetic / genetics*
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Receptors, Opioid, mu / genetics*
  • Receptors, Opioid, mu / metabolism*
  • Substantia Nigra / cytology
  • Substantia Nigra / metabolism


  • Protein Isoforms
  • Receptors, Opioid, mu
  • Dopamine