Enkephalins, dynorphins, and β‐endorphin in the rat dorsal horn: An immunofluorescence colocalization study

Abstract

To characterize neuronal pathways that release opioid peptides in the rat dorsal horn, multiplelabel immunohistochemistry, confocal microscopy and computerized colocalization measures were used to characterize opioid-containing terminals and cells. An antibody that selectively recognized β-endorphin labeled fibers and neurons in the ventral horn, fibers in the lateral funiculus and lamina X, but practically no fibers in the dorsal horn. An anti-enkephalin antibody, which recognized Leu-, Met-and Phe-Arg-Met-enkephalin, labeled the dorsolateral funiculus and numerous puncta in laminae I-III and V of the dorsal horn. An antibody against Phe-Arg-Metenkephalin, which did not recognize Leu-and Met-enkephalin, labeled the same puncta. Antibodies against dynorphin and prodynorphin labeled puncta and fibers in laminae I, II and V, and some fibers in the rest of the dorsal horn. Dynorphin and prodynorphin immunoreactivities colocalized in some puncta and fibers, but the prodynorphin antibody additionally labeled cell bodies. There was no colocalization of dynorphin (or prodynorphin) with enkephalin (or Phe-ArgMet-enkephalin). Enkephalin immunoreactivity did not colocalize with the C-fibers markers CGRP, substance P and isolectin B4. In contrast, there was some colocalization of dynorphin and prodynorphin with CGRP and substance P, but not with isolectin B4. Both enkephalin and dynorphin partly colocalized with vesicular glutamate transporter 2, a marker of glutamatergic terminals. The prodynorphin-positive neurons in the dorsal horn were distinct from neurons expressing μ-opioid receptors, neurokinin 1 receptors and protein kinase C-γ. These results show that enkephalins and dynorphins are present in different populations of dorsal horn neurons. In addition, dynorphin is present in some C-fibers.

Proteasome Targeted Therapies in Rheumatoid Arthritis

“…This agrees with other observations that the altered expression of SP and CGRP is critical for the modulation of pain and inflammation (Ambalavanar et al, 2006;Hutchins et al, 2000). Moreover, it has been reported that peripheral inflammation induces a dramatic up-regulation of PDYN biosynthesis in nociceptive neurons of the spinal dorsal horn (Przewlocki, 1987;Marvizon et al, 2009). As a future perspective it will be interesting to observe the effects of proteasome inhibition in the DRG and SC in inflammation.…”

The Development and Maintenance of Paclitaxel-induced Neuropathic Pain Require Activation of the Sphingosine 1-Phosphate Receptor Subtype 1

“…Sections treated with rabbit IgG at equivalent concentrations to primary antibodies were used as controls yielding only nonspecific background fluorescence. The fluorescence intensity of immunolabeled ceramide was calculated as reported previously (34,35,37) in selected regions of the lumbar spinal cord. The mean fluorescence intensity (MFI) was calculated by Equation 1,…”

Estrogenic influences in pain processing

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