Morphological features of endomorphin-2-immunoreactive ultrastructures in the dorsal root ganglion and spinal dorsal horn of the rat

Lu, Ya-Cheng; Yin, Jun-Bin; Bai, Yang; Li, Xia; Zhang, Ting; Yang, Juan; Yi, Xi-Nan; Zhang, Mingming; Li, Yunqing

doi:10.1016/j.jchemneu.2022.102142

Cited by 3 publications

(5 citation statements)

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“…In this situation, we also did not observe EM2-ir cell bodies in the SDH. By using immunoelectron microscopy, the ultrastructures that EM2 was expressed in the inherent neurons in the SDH were not observed, either ( Lu et al, 2022 ).…”

Section: Discussionmentioning

confidence: 99%

“…The procedures for staining of EM2-, MOR-, SP-, VGLUT2-, and GAD67-ir profiles were the same as our previous studies ( Yin et al, 2018 ; Lu et al, 2022 ). All of the antisera used are presented in Table 2 .…”

Section: Methodsmentioning

confidence: 99%

“…Endomorphin (EM) had remarkable affinity and selectivity for the μ-opioid receptor (MOR), which included EM1 (Tyr-Pro-Trp-Phe-NH2) and EM2 (Tyr-Pro-Phe-Phe-NH2) ( Zadina et al, 1997 ; Gu et al, 2017 ). It was considered that EM1 played an important role in brain nucleus such as the periaqueductal gray ( Chen et al, 2016 ), while EM2 mainly functioned in the spinal dorsal horn (SDH) ( Tseng et al, 2000 ; Yin et al, 2018 ; Lu et al, 2022 ). EM2 plays a pivotal role in inhibiting nociceptive information transmission at the spinal cord level ( Stone et al, 1997 ; Zadina et al, 1997 ).…”

Section: Introductionmentioning

confidence: 99%

“…EM2 plays a pivotal role in inhibiting nociceptive information transmission at the spinal cord level ( Stone et al, 1997 ; Zadina et al, 1997 ). EM2-immunoreactive (-ir) fibers existed in the superficial lamina of the SDH ( Yin et al, 2018 ; Lu et al, 2022 ), which was released following the dorsal root entry zone receiving electrical stimulation ( Williams et al, 1999 ; Heinke et al, 2011 ). Intrathecal ( i.t. )…”

Section: Introductionmentioning

confidence: 99%

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Morphological investigations of endomorphin-2 and spinoparabrachial projection neurons in the spinal dorsal horn of the rat

Yin

et al. 2022

Front. Neuroanat.

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It has been proved that endomorphin-2 (EM2) produced obvious analgesic effects in the spinal dorsal horn (SDH), which existed in our human bodies with remarkable affinity and selectivity for the μ-opioid receptor (MOR). Our previous study has demonstrated that EM2 made synapses with the spinoparabrachial projection neurons (PNs) in the SDH and inhibited their activities by reducing presynaptic glutamate release. However, the morphological features of EM2 and the spinoparabrachial PNs in the SDH have not been completely investigated. Here, we examined the morphological features of EM2 and the spinoparabrachial PNs by using triple fluorescence and electron microscopic immunohistochemistry. EM2-immunoreactive (-ir) afferents directly contacted with the spinoparabrachial PNs in lamina I of the SDH. Immunoelectron microscopy (IEM) were used to confirm that these contacts were synaptic connections. It was also observed that EM2-ir axon terminals contacting with spinoparabrachial PNs in lamina I contained MOR, substance P (SP) and vesicular glutamate transporter 2 (VGLUT2). In lamina II, MOR-ir neurons were observed to receive direct contacts from EM2-ir varicosities. The synaptic connections among EM2, MOR, SP, VGLUT2, and the spinoparabrachial PNs were also confirmed by IEM. In sum, our results supply morphological evidences for the analgesic effects of EM2 on the spinoparabrachial PNs in the SDH.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Morphological investigations of endomorphin-2 and spinoparabrachial projection neurons in the spinal dorsal horn of the rat

Yin

et al. 2022

Front. Neuroanat.

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“…Their co-expression was analyzed by randomly selecting two sections of the TG and us-ty. In these ganglia, EM-2-containing neurons have small-to-medium-sized cell bodies (Niu et al 2009;Lu et al 2022). Although EM-2's antinociceptive function in the sensory neurons of the spinal and vagal nerves is recognized, knowledge regarding the EM-1 distribution and function in the peripheral nervous system is limited.…”

Section: Methodsmentioning

confidence: 99%

Distribution and anti-nociceptive function of endomorphin-1 in the rat cranial sensory ganglia

SATO,

YAJIMA

et al. 2024

Biomed. Res.

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Distribution of endomorphin-1 (EM-1) was immunohistochemically investigated in the rat cranial sensory ganglia. Small to medium-sized neurons in the trigeminal (TG), petrosal (PG), and jugular ganglia (JG) expressed EM-1-immunoreactivity. However, EM-1-immunoreactive (-ir) neurons were infrequent in the nodose ganglion. In the brainstem, EM-1-ir varicose fibers were detected in the superficial layer of the medullary dorsal horn and the caudal part of the nucleus tractus solitarius. By trichrome immunofluorescence analysis, approximately 70% of EM-1-ir neurons were also immunoreactive for transient receptor potential vanilloid 1 (TRPV1) in all the examined ganglia. Additionally, 56.8% of EM1-ir TG neurons and approximately 30% of EM-1-ir PG and JG neurons showed calcitonin gene-related peptide (CGRP)-immunoreactivity. By a retrograde tracing method, several TG, PG, and JG neurons innervating the facial and external ear canal skin expressed EM-1-immunoreactivity. However, EM-1-ir neurons innervating the tooth pulp, circumvallate papilla, and pharynx were relatively rare. Thus, EM-1 expression and its coexistence with TRPV1 and CGRP in the cranial sensory neurons may depend on their various peripheral targets. EM1-ir neurons probably project to the superficial layer of the medullary dorsal horn and caudal part of the nucleus tractus solitarius. EM-1 may be involved in nociceptive transmission from the skin.

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Endogenous opiates and behavior: 2022

Bodnar

2023

Peptides

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Morphological features of endomorphin-2-immunoreactive ultrastructures in the dorsal root ganglion and spinal dorsal horn of the rat

Cited by 3 publications

References 51 publications

Morphological investigations of endomorphin-2 and spinoparabrachial projection neurons in the spinal dorsal horn of the rat

Morphological investigations of endomorphin-2 and spinoparabrachial projection neurons in the spinal dorsal horn of the rat

Distribution and anti-nociceptive function of endomorphin-1 in the rat cranial sensory ganglia

Endogenous opiates and behavior: 2022

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