Differential distribution in rat brain of mu opioid receptor carboxy terminal splice variants MOR-1C-like and MOR-1-like immunoreactivity: evidence for region-specific processing.
The present study examined immunohistochemically the regional distribution of the mu opioid receptor splice variant MOR-1C by using a rabbit antisera generated against the C-terminal peptide sequences and compared it with MOR-1. Overall, the distribution of MOR-1C-like immunoreactivity (-LI) differed from MOR-1-LI. Both MOR-1C-LI and MOR-1-LI were prominent in a few central nervous system regions, including the lateral parabrachial nucleus, the periaqueductal gray, and laminae I-II of the spinal trigeminal nuclei and the spinal cord. In the striatum, hippocampal formation, presubiculum and parasubiculum, amygdaloid nuclei, thalamic nuclei, locus coeruleus, and nucleus ambiguous MOR-1-LI predominated, whereas MOR-1C-LI was absent or sparse. Conversely, MOR-1C-LI exceeded MOR-1-LI in the lateral septum, the deep laminae of the spinal cord, and most hypothalamic nuclei such as the median eminence, periventricular, suprachiasmatic, supraoptic, arcuate, paraventricular, ventromedial, and dorsomedial nuclei. Double-labeling studies showed colocalization of the two receptors in neurons of the lateral septum, but not in the median eminence or in the arcuate nucleus, even though both MOR-1 isoforms were expressed. Because both MOR-1 and MOR-1C are derived from the same gene, these differences in regional distribution represent region-specific mRNA processing. The regional distributions reported in this study involve the epitope seen by the combinations of exons 7, 8, and 9. However, if other MOR-1 variants containing exons 7, 8, and 9 exist, the antisera would not distinguish between them and MOR-1C.
Abbadie
C
C
The Cotzias Laboratory of Neuro-Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
Pan
Y X
YX
Pasternak
G W
GW
D017398:Alternative Splicing; D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001921:Brain / Q000378:metabolism*; D016466:CHO Cells; D002490:Central Nervous System / Q000378:metabolism; D006224:Cricetinae; D004274:DNA, Recombinant; D014644:Genetic Variation; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D051381:Rats / Q000378:metabolism*; D017450:Receptors, Opioid, mu / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution
D004274:DNA, Recombinant; D010446:Peptide Fragments; D017450:Receptors, Opioid, mu