Involvement of A5/A7 noradrenergic neurons and B2 serotonergic neurons in nociceptive processing:a fiber photometry study

In the central nervous system,the A6 noradrenaline(NA)and the B3 serotonin(5-HT)cell groups are well-recognized players in the descending antinociceptive system,while other NA/5-HT cell groups are not well characterized.A5/A7 NA and B25-HT cells project to the spinal horn and form descending pathways.We recorded G-Ca MP6 green fluorescence signal intensities in the A5/A7 NA and the B25-HT cell groups of awake mice in response to acute tail pinch stimuli,acute heat stimuli,and in the context of a non-noxious control test,using fiber photometry with a calcium imaging system.We first introduced G-Ca MP6 in the A5/A7 NA or B25-HT neuronal soma,using transgenic mice carrying the tetracycline-controlled transactivator transgene under the control of either a dopamineβ-hydroxylase or a tryptophan hydroxylase-2 promoters and by the site-specific injection of adeno-associated virus(AAV-Tet O(3 G)-G-Ca MP6).After confirming the specific expression patterns of G-Ca MP6,we recorded G-Ca MP6 green fluorescence signals in these sites in awake mice in response to acute nociceptive stimuli.G-Ca MP6 fluorescence intensity in the A5,A7,and B2 cell groups was rapidly increased in response to acute nociceptive stimuli and soon after,it returned to baseline fluorescence intensity.This was not observed in the non-noxious control test.The results indicate that acute nociceptive stimuli rapidly increase the activities of A5/A7 NA or B25-HT neurons but the non-noxious stimuli do not.The present study suggests that A5/A7 NA or B25-HT neurons play important roles in nociceptive processing in the central nervous system.We suggest that A5/A7/B2 neurons may be new therapeutic targets.All performed procedures were approved by the Institutional Animal Use Committee of Kagoshima University(MD17105)on February 22,2018.

A13 dopamine cell group in the zona incerta is a key neuronal nucleus in nociceptive processing

In stressful modern society, pain caused by physical and mental disorders is an increasing social health problem all over the world.Physical and mental activity depends on the state of various neurotransmitters in the central nervous system(CNS).Monoaminergic systems play important roles in regulating physiological functions including nociception.It is well known that in the CNS, there are descending pathways related to nociceptive processing known as the descending antinociceptive system(DAS).Noradrenalin and serotonin are major components of the DAS that form the locus coeruleus(LC)-spinal dorsal horn noradrenergic circuit and periaqueductal gray(PAG)-rostro ventricular medulla(RVM)-spinal dorsal horn serotonergic circuit(Jordan et al., 2008).Dopaminergic pathways also play roles in regulating nociceptive processing in the CNS.

Transient Receptor Potential Ankyrin 1 Ion Channel Facilitates Acute Inflammation Induced by Surgical Incision in Mice

Background: Transient receptor potential ankyrin (TRPA) 1 is known as a peripheral initiator of acute inflammation and hyperalgesia. However, its role in the facilitation of innate immune responses followed by resolution of the inflammation triggered by a surgical incision has not been fully investigated. Therefore, we evaluated the mechanism by which TRPA1 regulates the inflammatory responses mainly facilitated by neutrophils and macrophages in the early course of wound repair after an incision. Methods: Plantar incision was performed in wild-type and TRPA1-/- mice. The infiltration of polymorphonuclear neutrophils, macrophage phenotype, and induction of inflammatory mediators were assessed for 7 days postoperatively. Results: TRPA1-/-?mice exhibited decreased infiltration of polymorphonuclear neutrophilscompared with wild-type mice on day 1. Consistently, the influx of F4/80+ iNOS+ proinflammatory M1 macrophages to incised sites was markedly decreased on day 2. Similarly, F4/80+ CD206+M2 macrophages, which regulate the resolution of inflammation and promote wound healing in the later phase of acute inflammation, were significantly decreased in TRPA1-/- compared with those in wild-type mice on day 7. In addition, the induction of heme oxygenase-1, which promotes wound healing by switching phenotype of macrophages, was decreased in the early phase of acute inflammation, whereas the expression of proinflammatory mediators such as tumor necrosis factor and cyclooxygenase-2, and 15-lipoxygenase, which are involved in the resolution of inflammation was increased in the late phase in TRPA1-/- mice. Conclusions: Early innate immune responses including neutrophil infiltration and macrophage polarization at incised sites were inhibited in TRPA1-/- mice, associated with increased pro-inflammatory mediators in later phase. Peripheral TRPA1 may facilitate the acute inflammatory process, leading to the promotion of macrophage-mediated resolution of inflammation and wound repair after a surgical incision.