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Activity-dependent silencing reveals functionally distinct itch-generating sensory neurons
The peripheral terminals of primary sensory neurons detect histamine and non-histamine itch-provoking ligands through molecularly distinct transduction mechanisms. It remains unclear, however, whether these distinct pruritogens activate the same or different afferent fibers. We utilized a strategy of reversibly silencing specific subsets of murine pruritogen-sensitive sensory axons by targeted delivery of a charged sodium-channel blocker and found that functional blockade of histamine itch did not affect the itch evoked by chloroquine or SLIGRL-NH2, and vice versa. Notably, blocking itch-generating fibers did not reduce pain-associated behavior. However, silencing TRPV1+ or TRPA1+ neurons allowed AITC or capsaicin respectively to evoke itch, implying that certain peripheral afferents may normally indirectly inhibit algogens from eliciting itch. These findings support the presence of functionally distinct sets of itch-generating neurons and suggest that targeted silencing of activated sensory fibers may represent a clinically useful anti-pruritic therapeutic approach for histaminergic and non-histaminergic pruritus
Cowper's syringocele: A rare differential diagnosis of infravesical obstruction in boys and young adults
Objective and introduction Cowper's syringocele is a cystic dilation of the bulbourethral gland duct, initially defined by Maizels et al. in 1983. Although obstructive and non-obstructive types of this rare anomaly are described, clinical symptoms are highly unspecific. Therefore, we report 12 cases of children and young adults diagnosed with Cowper's syringocele to further clarify clinical course, comorbidity and treatment strategies. Study design We retrospectively collected clinical data of 12 children and young adults from birth to 18.5 years (median 7.2 years) who had been treated in four different institutes during a period of 16 years. The primary specific diagnostic work-up consisted of ultrasound, cystourethrography, and cystoscopy. Results 3Older patients with a median age of 11.8 years clinically presented with obstructive voiding pattern or gross hematuria; infants with a median age of 0.6 years presented with febrile urinary tract infections (UTIs). After cystoscopic confirmation in all patients, endoscopic treatment was possible in nine; open surgical resection was necessary in three patients. Because of intrauterine megacystis and chronic renal failure, one boy underwent suprapubic diversion with a cystostomy soon after birth. Owing to urological comorbidity or later complications, additional procedures were necessary, for example, resection of minor urethral valves, prophylactic circumcision for UTI, endoscopic or open antireflux procedures, and occasionally complex bladder reconstructions in the long term. Discussion According to our data, the initial clinical symptoms of Cowper's syringocele were related to presenting age rather than the previously described type of syringocele according to Maizels et al. Infants presented with febrile UTIs; however, older boys and young adults had mainly voiding problems or nocturnal enuresis. Therefore, the clinical significance of the described syringocele types must be questioned. Eighty-three percent of our patients showed additional urological pathology such as vesicoureterorenal reflux, ureteropelvic junction obstruction, megaureter, or minor urethral valves. Thus, Cowper's syringocele hardly seems to be an isolated pathology. Conclusion Although rare, Cowper's syringoceles should be considered in differential diagnosis of infravesical obstruction in boys and young adults. Diagnostics are usually justified by presenting symptoms such as UTI or urinary flow impairment, which seem to be age dependent. Despite modern diagnostic tools, diagnosis is usually made by cystourethrography and sometimes accidentally by cystoscopy. Considerable urological comorbidities and consecutive bladder dysfunction need long-term follow-up. [GRAPHICS