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Synaptic connections between endomorphin 2-immunoreactive terminals and μ-opioid receptor-expressing neurons in the sacral parasympathetic nucleus of the rat.

Dou XL, Qin RL, Qu J, Liao YH, Lu Yc, Zhang T, Shao C, Li YQ - PLoS ONE (2013)

Bottom Line: All of the them also expressed MOR.These results provided morphological evidence that EM2-containing axon terminals formed symmetric synapses with MOR-expressing PPNs in the SPN.The present results also show that EM2 and MOR might be involved in both the homeostatic control and information transmission of micturition.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Xijing Hospital, The Fourth Military Medical University, Xi'an, China.

ABSTRACT
The urinary bladder is innervated by parasympathetic preganglionic neurons (PPNs) that express μ-opioid receptors (MOR) in the sacral parasympathetic nucleus (SPN) at lumbosacral segments L6-S1. The SPN also contains endomorphin 2 (EM2)-immunoreactive (IR) fibers and terminals. EM2 is the endogenous ligand of MOR. In the present study, retrograde tract-tracing with cholera toxin subunit b (CTb) or wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) via the pelvic nerve combined with immunohistochemical staining for EM2 and MOR to identify PPNs within the SPN as well as synaptic connections between the EM2-IR terminals and MOR-expressing PPNs in the SPN of the rat. After CTb was injected into the pelvic nerve, CTb retrogradely labeled neurons were almost exclusively located in the lateral part of the intermediolateral gray matter at L6-S1 of the lumbosacral spinal cord. All of the them also expressed MOR. EM2-IR terminals formed symmetric synapses with MOR-IR, WGA-HRP-labeled and WGA-HRP/MOR double-labeled neuronal cell bodies and dendrites within the SPN. These results provided morphological evidence that EM2-containing axon terminals formed symmetric synapses with MOR-expressing PPNs in the SPN. The present results also show that EM2 and MOR might be involved in both the homeostatic control and information transmission of micturition.

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The connections between EM2-IR axon terminals and CTb/MOR double-labeled neurons in the SPN on a transverse section at S1.A2, B2, C2 and D2 are enlargements of the rectangles delineated on A1, B1, C1, D1, respectively. After injecting CTb into the pelvic nerve, CTb-labeled neurons were found in the SPN (A1, A2). Several CTb-labeled neurons contacted EM2-IR fibers and terminals (B1, B2; D1, D2) and also exhibited MOR-immunoreactivity (C1, C2; D1, D2). The white arrow points to suggestive close appositions between EM2-IR axon terminals and a CTb/MOR double-labeled neuron. The scale bars indicate 50 µm in A1, B1, C1 and D1 and 20 µm in A2, B2, C2 and D2.
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pone-0062028-g004: The connections between EM2-IR axon terminals and CTb/MOR double-labeled neurons in the SPN on a transverse section at S1.A2, B2, C2 and D2 are enlargements of the rectangles delineated on A1, B1, C1, D1, respectively. After injecting CTb into the pelvic nerve, CTb-labeled neurons were found in the SPN (A1, A2). Several CTb-labeled neurons contacted EM2-IR fibers and terminals (B1, B2; D1, D2) and also exhibited MOR-immunoreactivity (C1, C2; D1, D2). The white arrow points to suggestive close appositions between EM2-IR axon terminals and a CTb/MOR double-labeled neuron. The scale bars indicate 50 µm in A1, B1, C1 and D1 and 20 µm in A2, B2, C2 and D2.

Mentions: On preparations exhibiting double immunofluorescence labeling, EM2-IR axon terminals appeared to be closely apposed with MOR-IR neuronal cell bodies and their dendritic processes in the SPN (Figures 3C1, C2). To provide morphological confirmation that the MOR-IR neurons were PPNs, immunofluorescence histochemical triple-labeling was performed. Initially, neurons in the SPN were successfully identified using CTb retrograde transport tracing (Figures 4A1, A2). We observed that all of the CTb-labeled neurons demonstrated MOR-IR staining (Figures 4C1, C2), and the EM2-IR fibers and terminals were distributed throughout the SPN (Figures 4B1, B2). Moreover, we observed beaded-like EM2-IR fibers with varicosities (Figures 3A2, 4B2), and the EM2-IR terminals appeared to be closely apposed with the CTb-labeled neurons, which were MOR-immunopositive in the SPN (Figures 4D1, D2).


Synaptic connections between endomorphin 2-immunoreactive terminals and μ-opioid receptor-expressing neurons in the sacral parasympathetic nucleus of the rat.

Dou XL, Qin RL, Qu J, Liao YH, Lu Yc, Zhang T, Shao C, Li YQ - PLoS ONE (2013)

The connections between EM2-IR axon terminals and CTb/MOR double-labeled neurons in the SPN on a transverse section at S1.A2, B2, C2 and D2 are enlargements of the rectangles delineated on A1, B1, C1, D1, respectively. After injecting CTb into the pelvic nerve, CTb-labeled neurons were found in the SPN (A1, A2). Several CTb-labeled neurons contacted EM2-IR fibers and terminals (B1, B2; D1, D2) and also exhibited MOR-immunoreactivity (C1, C2; D1, D2). The white arrow points to suggestive close appositions between EM2-IR axon terminals and a CTb/MOR double-labeled neuron. The scale bars indicate 50 µm in A1, B1, C1 and D1 and 20 µm in A2, B2, C2 and D2.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3643968&req=5

pone-0062028-g004: The connections between EM2-IR axon terminals and CTb/MOR double-labeled neurons in the SPN on a transverse section at S1.A2, B2, C2 and D2 are enlargements of the rectangles delineated on A1, B1, C1, D1, respectively. After injecting CTb into the pelvic nerve, CTb-labeled neurons were found in the SPN (A1, A2). Several CTb-labeled neurons contacted EM2-IR fibers and terminals (B1, B2; D1, D2) and also exhibited MOR-immunoreactivity (C1, C2; D1, D2). The white arrow points to suggestive close appositions between EM2-IR axon terminals and a CTb/MOR double-labeled neuron. The scale bars indicate 50 µm in A1, B1, C1 and D1 and 20 µm in A2, B2, C2 and D2.
Mentions: On preparations exhibiting double immunofluorescence labeling, EM2-IR axon terminals appeared to be closely apposed with MOR-IR neuronal cell bodies and their dendritic processes in the SPN (Figures 3C1, C2). To provide morphological confirmation that the MOR-IR neurons were PPNs, immunofluorescence histochemical triple-labeling was performed. Initially, neurons in the SPN were successfully identified using CTb retrograde transport tracing (Figures 4A1, A2). We observed that all of the CTb-labeled neurons demonstrated MOR-IR staining (Figures 4C1, C2), and the EM2-IR fibers and terminals were distributed throughout the SPN (Figures 4B1, B2). Moreover, we observed beaded-like EM2-IR fibers with varicosities (Figures 3A2, 4B2), and the EM2-IR terminals appeared to be closely apposed with the CTb-labeled neurons, which were MOR-immunopositive in the SPN (Figures 4D1, D2).

Bottom Line: All of the them also expressed MOR.These results provided morphological evidence that EM2-containing axon terminals formed symmetric synapses with MOR-expressing PPNs in the SPN.The present results also show that EM2 and MOR might be involved in both the homeostatic control and information transmission of micturition.

View Article: PubMed Central - PubMed

Affiliation: Department of Urology, Xijing Hospital, The Fourth Military Medical University, Xi'an, China.

ABSTRACT
The urinary bladder is innervated by parasympathetic preganglionic neurons (PPNs) that express μ-opioid receptors (MOR) in the sacral parasympathetic nucleus (SPN) at lumbosacral segments L6-S1. The SPN also contains endomorphin 2 (EM2)-immunoreactive (IR) fibers and terminals. EM2 is the endogenous ligand of MOR. In the present study, retrograde tract-tracing with cholera toxin subunit b (CTb) or wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) via the pelvic nerve combined with immunohistochemical staining for EM2 and MOR to identify PPNs within the SPN as well as synaptic connections between the EM2-IR terminals and MOR-expressing PPNs in the SPN of the rat. After CTb was injected into the pelvic nerve, CTb retrogradely labeled neurons were almost exclusively located in the lateral part of the intermediolateral gray matter at L6-S1 of the lumbosacral spinal cord. All of the them also expressed MOR. EM2-IR terminals formed symmetric synapses with MOR-IR, WGA-HRP-labeled and WGA-HRP/MOR double-labeled neuronal cell bodies and dendrites within the SPN. These results provided morphological evidence that EM2-containing axon terminals formed symmetric synapses with MOR-expressing PPNs in the SPN. The present results also show that EM2 and MOR might be involved in both the homeostatic control and information transmission of micturition.

Show MeSH
Related in: MedlinePlus