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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 distribution patterns of CTb labeled PPNs in the SPN at L6-S1 after CTb was injected into the left pelvic nerve.(A) The location of the CTb-labeled neurons in the SPN at S1. (A′) An enlarged image of (A), showing the extending directions of the dendrites of the CTb-labeled neurons in the lateral band (LB) or dorsal band (DB) (arrows); A″ is also an enlarged image of A, in which CTb-labeled neurons in the SPN belong to 3 groups: DB, LB and internal band (IB) (outside of the two circles). In the longitudinal sections (B), CTb-labeled neuronal clusters in the SPN resemble a “string of beads.” C: CTb-labeled neurons in the SPN in one rat are arranged in a sequence from the rostral to caudal levels of the nucleus. Scale bars indicate 200 µm in A and C, 100 µm in A′ and B and 50 µm in A″.
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pone-0062028-g001: The distribution patterns of CTb labeled PPNs in the SPN at L6-S1 after CTb was injected into the left pelvic nerve.(A) The location of the CTb-labeled neurons in the SPN at S1. (A′) An enlarged image of (A), showing the extending directions of the dendrites of the CTb-labeled neurons in the lateral band (LB) or dorsal band (DB) (arrows); A″ is also an enlarged image of A, in which CTb-labeled neurons in the SPN belong to 3 groups: DB, LB and internal band (IB) (outside of the two circles). In the longitudinal sections (B), CTb-labeled neuronal clusters in the SPN resemble a “string of beads.” C: CTb-labeled neurons in the SPN in one rat are arranged in a sequence from the rostral to caudal levels of the nucleus. Scale bars indicate 200 µm in A and C, 100 µm in A′ and B and 50 µm in A″.

Mentions: In the present study, after CTb injection into the left pelvic nerve, CTb retrogradely labeled PPNs were almost exclusively found in the lateral edge of the intermediolateral column in the left gray matter at L6-S1 (Figure 1A). These CTb-labeled neurons were generally located in or near the intermediolateral nucleus. In transverse sections, CTb-labeled neurons could be clearly divided into three groups. The LB group was located in the dorsolateral portion of the SPN and contained neurons of various shapes (Figure 1A″), including spindle-shaped neurons, rotund neurons and triangular neurons. Dendrites of the neurons in this band extended along the lateral marginal zone of the dorsal horn and into the dorsolateral funiculus (Figure 1A′). In contrast, the DB group was located deeper within the spinal cord and comprised of radially oriented neurons with dendrites that extended medially into the dorsal gray commissure (Figure 1A′). The distributions of the CTb-labeled neurons in the longitudinal (Figure 1B) and transverse (Figure 1C) sections further elucidated the columnar structure of the CTb-labeled PPNs in the SPN, which consisted of neuronal cell clusters that resembled “strings of beads.” The clusters had an average length of 2850±120 µm. In the ipsilateral SPN at L6-S1, approximately 630±21 medium-sized CTb retrograde-labeled neurons, of which the sizes ranged from 8–13 µm (shorter axis) to 10–22 µm (longer axis), were observed in each rat. The number of CTb retrograde-labeled neurons dramatically increased between the middle section of L6 and the middle section of S1, reaching its peak in the upper and middle parts of S1, and then gradually decreased until it disappeared completely in the lower part of S1.


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 distribution patterns of CTb labeled PPNs in the SPN at L6-S1 after CTb was injected into the left pelvic nerve.(A) The location of the CTb-labeled neurons in the SPN at S1. (A′) An enlarged image of (A), showing the extending directions of the dendrites of the CTb-labeled neurons in the lateral band (LB) or dorsal band (DB) (arrows); A″ is also an enlarged image of A, in which CTb-labeled neurons in the SPN belong to 3 groups: DB, LB and internal band (IB) (outside of the two circles). In the longitudinal sections (B), CTb-labeled neuronal clusters in the SPN resemble a “string of beads.” C: CTb-labeled neurons in the SPN in one rat are arranged in a sequence from the rostral to caudal levels of the nucleus. Scale bars indicate 200 µm in A and C, 100 µm in A′ and B and 50 µm in A″.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3643968&req=5

pone-0062028-g001: The distribution patterns of CTb labeled PPNs in the SPN at L6-S1 after CTb was injected into the left pelvic nerve.(A) The location of the CTb-labeled neurons in the SPN at S1. (A′) An enlarged image of (A), showing the extending directions of the dendrites of the CTb-labeled neurons in the lateral band (LB) or dorsal band (DB) (arrows); A″ is also an enlarged image of A, in which CTb-labeled neurons in the SPN belong to 3 groups: DB, LB and internal band (IB) (outside of the two circles). In the longitudinal sections (B), CTb-labeled neuronal clusters in the SPN resemble a “string of beads.” C: CTb-labeled neurons in the SPN in one rat are arranged in a sequence from the rostral to caudal levels of the nucleus. Scale bars indicate 200 µm in A and C, 100 µm in A′ and B and 50 µm in A″.
Mentions: In the present study, after CTb injection into the left pelvic nerve, CTb retrogradely labeled PPNs were almost exclusively found in the lateral edge of the intermediolateral column in the left gray matter at L6-S1 (Figure 1A). These CTb-labeled neurons were generally located in or near the intermediolateral nucleus. In transverse sections, CTb-labeled neurons could be clearly divided into three groups. The LB group was located in the dorsolateral portion of the SPN and contained neurons of various shapes (Figure 1A″), including spindle-shaped neurons, rotund neurons and triangular neurons. Dendrites of the neurons in this band extended along the lateral marginal zone of the dorsal horn and into the dorsolateral funiculus (Figure 1A′). In contrast, the DB group was located deeper within the spinal cord and comprised of radially oriented neurons with dendrites that extended medially into the dorsal gray commissure (Figure 1A′). The distributions of the CTb-labeled neurons in the longitudinal (Figure 1B) and transverse (Figure 1C) sections further elucidated the columnar structure of the CTb-labeled PPNs in the SPN, which consisted of neuronal cell clusters that resembled “strings of beads.” The clusters had an average length of 2850±120 µm. In the ipsilateral SPN at L6-S1, approximately 630±21 medium-sized CTb retrograde-labeled neurons, of which the sizes ranged from 8–13 µm (shorter axis) to 10–22 µm (longer axis), were observed in each rat. The number of CTb retrograde-labeled neurons dramatically increased between the middle section of L6 and the middle section of S1, reaching its peak in the upper and middle parts of S1, and then gradually decreased until it disappeared completely in the lower part of S1.

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