Infantile tissue injury induces sensory deficits in adulthood. Infantile facial incision (IFI) was reported to cause an enhancement of incision-induced mechanical hypersensitivity in adulthood due to acceleration of the trigeminal ganglion neuronal excitability. However, the effects of IFI on activation of microglia in the spinal trigeminal nucleus and its involvement in facial pain sensitivity is not well known. Methods: A facial skin incision was made in the left whisker pad in infant (IFI) and/or adult rats (AFI). Mechanical head withdrawal threshold and microglial activation in the trigeminal spinal nucleus were analyzed. Results: Mechanical pain hypersensitivity induced by AFI was significantly exacerbated and prolonged by IFI. The number of Iba1-immunoreactive cells in the trigeminal spinal nucleus following AFI was increased by IFI, suggesting that IFI facilitates microglial hyperactivation following AFI. Intraperitoneal administration of minocycline, a microglial activation inhibitor, suppressed the facial incision-induced microglial hyperactivation in the trigeminal spinal nucleus and the exacerbation of the facial mechanical pain hypersensitivity induced by IFI. Conclusion: These results suggest that facial trauma in infants causes hyperactivation of microglia in the trigeminal spinal nucleus following AFI, leading to the prolongation of the facial mechanical pain hypersensitivity.
We evaluated the mechanisms underlying the oxytocin (OXT)-induced analgesic effect on orofacial neuropathic pain following infraorbital nerve injury (IONI). IONI was established through tight ligation of one-third of the infraorbital nerve thickness. Subsequently, the head withdrawal threshold for mechanical stimulation (MHWT) of the whisker pad skin was measured using a von Frey filament. Trigeminal ganglion (TG) neurons innervating the whisker pad skin were identified using a retrograde labeling technique. OXT receptor-immunoreactive (IR), transient receptor potential vanilloid 1 (TRPV1)-IR, and TRPV4-IR TG neurons innervating the whisker pad skin were examined on post-IONI day 5. The MHWT remarkably decreased from post-IONI day 1 onward. OXT application to the nerve-injured site attenuated the decrease in MHWT from day 5 onward. TRPV1 or TRPV4 antagonism significantly suppressed the decrement of MHWT following IONI. OXT receptors were expressed in the uninjured and Fluoro-Gold (FG)-labeled TG neurons. Furthermore, there was an increase in the number of FG-labeled TRPV1-IR and TRPV4-IR TG neurons, which was inhibited by administering OXT. This inhibition was suppressed by co-administration with an OXT receptor antagonist. These findings suggest that OXT application inhibits the increase in TRPV1-IR and TRPV4-IR TG neurons innervating the whisker pad skin, which attenuates post-IONI orofacial mechanical allodynia.
A case of delayed epistaxis from the mucosa behind the right side of the inferior nasal mucosa 11 days after orthognathic surgery by Le Fort I osteotomy is presented. The patient was a 31-year-old man who underwent orthognathic surgery under general anesthesia. No abnormal findings were found during or after the operation. The patient was discharged from the hospital 10 days postoperatively. However, bleeding from the right nasal cavity occurred suddenly on the night after discharge, and he presented to our hospital again. The epistaxis was stopped once by nasal packing containing 0.001% epinephrine and systemic infusion of carbazochrome sulfonic acid and tranexamic acid. However, when the nasal packing was removed the next day, right nasal epistaxis was observed again. Curvature of the nasal septum and thickening of the inferior turbinate mucosa were seen on inspection; although, no active bleeding point was identified. Decreased nasal mucosa thickening and bleeding were observed after nasal packing containing 0.02% epinephrine. When the inside of the nasal cavity was observed endoscopically, an approximately 2 mm laceration was found in the mucosa behind the side wall of the right inferior nasal mucosa, and bleeding from the same part was confirmed. After endoscopic cauterization for hemostasis of the nasal mucosa, no rebleeding was observed. Although delayed epistaxis after Le Fort I osteotomy are often performed CT angiography to confirm the bleeding site, endoscopic cauterization would be primarily useful because of less invasiveness.
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