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Endomorphin-2 Inhibits the Activity of the Spinoparabrachial Projection Neuron through Presynaptic Mechanisms in the Spinal Dorsal Horn in Rats
- Source :
- Neurosignals, Vol 26, Iss 1, Pp 43-57 (2018)
- Publication Year :
- 2018
- Publisher :
- S. Karger AG, 2018.
-
Abstract
- Background/Aims: Spinal dorsal horn (SDH) is one of the most important regions for analgesia produced by endomorphin-2 (EM2), which has a higher affinity and specificity for the µ-opioid receptor (MOR) than morphine. Many studies have focused on substantia gelatinosa (SG, lamina II) neurons to elucidate the cellular basis for its antinociceptive effects. However, the complicated types and local circuits of interneurons in the SG make it difficult to understand the real effects of EM2. Therefore, in the present study, we examined the effects of EM2 on projection neurons (PNs) in lamina I. Methods: Tracing, immunofluoresence, and immunoelectron methods were used to examine the morphological connections between EM2-immunoreactive (-ir) terminals and PNs. By using in vitro whole cell patch clamp recording technique, we investigated the functional effects of EM2 on PNs. Results: EM2-ir afferent terminals directly contacted PNs projecting to the parabrachial nucleus in lamina I. Their synaptic connections were further confirmed by immunoelectron microscopy, most of which were asymmetric synapses. It was found that EM2 had a strong inhibitory effect on the frequency, but not amplitude, of the spontaneous excitatory postsynaptic current (sEPSC) of the spinoparabrachial PNs in lamina I, which could be reversed by MOR antagonist CTOP. However, their spontaneous inhibitory postsynaptic current (sIPSC) and intrinsic properties were not changed after EM2 application. Conclusion: Applying EM2 to the SDH could produce analgesia through inhibiting the activities of the spinoparabrachial PNs in lamina I by reducing presynaptic neurotransmitters release from the primary afferent terminals.
- Subjects :
- Spinal dorsal horn
Endomorphin
Parabrachial nucleus
Postsynaptic Current
Immunoelectron microscopy
030209 endocrinology & metabolism
Inhibitory postsynaptic potential
lcsh:RC346-429
03 medical and health sciences
Cellular and Molecular Neuroscience
chemistry.chemical_compound
0302 clinical medicine
Developmental Neuroscience
Patch clamp
Projection neuron
lcsh:Neurology. Diseases of the nervous system
Parabrachial Nucleus
Chemistry
lcsh:QP351-495
Presynaptic effect
lcsh:Neurophysiology and neuropsychology
Nociception
nervous system
Neurology
Excitatory postsynaptic potential
Rat
Neuroscience
030217 neurology & neurosurgery
Subjects
Details
- ISSN :
- 14248638 and 1424862X
- Volume :
- 26
- Database :
- OpenAIRE
- Journal :
- Neurosignals
- Accession number :
- edsair.doi.dedup.....b7a1ece5d84004c2fae4eff4c8b3096f