Synaptic connectivity of urinary bladder afferents in the rat superficial dorsal horn and spinal parasympathetic nucleus. Issue 18 (12th June 2019)

• Record Type: Journal Article
• Authors: Park, Sook Kyung; Devi, Angom Pushparani; Bae, Jin Young; Cho, Yi Sul; Ko, Hyoung‐Gon; Kim, Duk Yoon; Bae, Yong Chul
• Is Part Of: Journal of comparative neurology. Volume 527:Issue 18(2019)
• Page Start: 3002
• Page End: 3013
• Publication Date: 2019-06-12
• Subjects: axoaxonic synapse -- RRID: AB_10013220 -- RRID: AB_1769134 -- RRID: AB_2314443 -- RRID: AB_2314586 -- RRID: AB_2340411 -- spinal cord -- synaptic connectivity -- ultrastructure -- urinary bladder -- visceral afferent; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.24725
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: That visceral sensory afferents are functionally distinct from their somatic analogues has been known for a long time but the detailed knowledge of their synaptic connections and neurotransmitters at the first relay nucleus in the spinal cord has been limited. To provide information on these topics, we investigated the synapses and neurotransmitters of identified afferents from the urinary bladder to the superficial laminae of the rat spinal dorsal horn (DH) and the spinal parasympathetic nucleus (SPN) by tracing with horseradish peroxidase, quantitative electron microscopical analysis, and immunogold staining for GABA and glycine. In the DH, most bladder afferent boutons formed synapses with 1–2 postsynaptic dendrites, whereas in the SPN, close to a half of them formed synapses with 3–8 postsynaptic dendrites. The number of postsynaptic dendrites and dendritic spines per bladder afferent bouton, both measures of synaptic divergence and of potential for synaptic plasticity at a single bouton level, were significantly higher in the SPN than in the DH. Bladder afferent boutons frequently received inhibitory axoaxonic synapses from presynaptic endings in the DH but rarely in the SPN. The presynaptic endings were GABA‐ and/or glycine‐immunopositive. The bouton volume, mitochondrial volume, and active zone area, all determinants of synaptic strength, of the bladder afferent boutons were positively correlated with the number of postsynaptic dendrites. These findings suggest that visceral sensory information conveyed via the urinary bladder afferents is processed differently in the DH than in the SPN, and differently from the way somatosensory information is processed in the spinal cord. Abstract : We show that (a) synaptic connectivity of bladder afferents is different between in the spinal dorsal horn (DH) and parasympathetic nucleus (SPN), and from that of somatosensory afferents, (b) they receive axoaxonic synapses from GABAergic or glycinergic endings, and (c) their bouton volume is correlated with the postsynaptic dendrite number.