Endomorphin-2 is released from newborn rat primary sensory neurons in a frequency- and calcium-dependent manner

Heather L. Scanlin, Elizabeth A. Carroll, Victoria K. Jenkins, Agnieszka Balkowiec

Research output: Contribution to journalArticle

15 Scopus citations


Recent evidence indicates that endomorphins, endogenous mu-opioid receptor (MOR) agonists, modulate synaptic transmission in both somatic and visceral sensory pathways. Here we show that endomorphin-2 (END-2) is expressed in newborn rat dorsal root ganglion (DRG) and nodose-petrosal ganglion complex (NPG) neurons, and rarely co-localizes with brain-derived neurotrophic factor (BDNF). In order to examine activity-dependent release of END-2 from neurons, we established a model using dispersed cultures of DRG and NPG cells activated by patterned electrical field stimulation. To detect release of END-2, we developed a novel rapid capture enzyme-linked immunosorbent assay (ELISA), in which END-2 capture antibody was added to neuronal cultures shortly before their electrical stimulation. The conventional assay was effective at reliably detecting END-2 only when the cells were stimulated in the presence of CTAP, a MOR-selective antagonist. This suggests that the strength of the novel assay is related primarily to rapid capture of released END-2 before it binds to endogenous MORs. Using the rapid capture ELISA, we found that stimulation protocols known to induce plastic changes at sensory synapses were highly effective at releasing END-2. Removal of extracellular calcium or blocking voltage-activated calcium channels significantly reduced the release. Together, our data provide the first evidence that END-2 is expressed by newborn DRG neurons of all sizes found in this age group, and can be released from these, as well as from NPG neurons, in an activity-dependent manner. These results point to END-2 as a likely mediator of activity-dependent plasticity in sensory pathways.

Original languageEnglish (US)
Pages (from-to)2629-2642
Number of pages14
JournalEuropean Journal of Neuroscience
Issue number10
StatePublished - May 2008


  • Activity-dependent release
  • Dorsal root ganglion
  • Nodose-petrosal
  • Opiates

ASJC Scopus subject areas

  • Neuroscience(all)

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