Noroviruses as a major cause of acute gastroenteritis in children in Finland, 2009-2010.

Noroviruses are, after rotaviruses, the second most common cause of acute gastroenteritis in young children. In a prospective study conducted in 2009-2010 at the Tampere University Hospital, 195 stool specimens were collected from cases of acute gastroenteritis in children and examined for noroviruses, sapoviruses, and rotaviruses, using a reverse transcriptase polymerase chain reaction (RT-PCR). Noroviruses were found in 49 (25%) of the cases and sapoviruses in 12 (6%). The norovirus genotype GII.4 dominated with a 76% share; other genotypes detected were GII.7/GII.6 (16%), GII.g/GII.12, GII.e/GII.4, and GII.7 (2% each). For comparison, 47 (24%) cases of rotavirus gastroenteritis were diagnosed in the same period. In conclusion, after the introduction of rotavirus vaccination in Finland in September 2009, noroviruses have become as common as rotaviruses as the causative agents of acute gastroenteritis in young children, and are likely to become the leading cause. Norovirus GII.4 continues to be the dominant genotype.

Attenuation of mechanical hypersensitivity by an antagonist of the TRPA1 ion channel in diabetic animals.

BACKGROUND: The TRPA1 ion channel modulates excitability of nociceptors, and it may be activated by compounds resulting from oxidative insults. Diabetes mellitus produces oxidative stress and sensory neuropathy. The authors tested the hypothesis that diabetes-induced endogenous compounds acting on the TRPA1 ion channel contribute to development and maintenance of mechanical hypersensitivity. METHODS: Diabetes mellitus was induced by streptozotocin. Mechanical hypersensitivity was assessed by the monofilament and paw pressure tests. Chembridge-5861528 (CHEM; a TRPA1 channel antagonist, a derivative of HC-030031) or vehicle was administered acutely or twice daily for 10 days in diabetic animals. For comparison, effects of CHEM were assessed in a group of healthy control animals. RESULTS: Acute administration of CHEM attenuated mechanically induced withdrawal responses in diabetic and control groups. The maximal effect (over 50% elevation of the paw pressure threshold) by acute administration of CHEM was obtained in 30 min. The lowest dose producing a significant attenuation was 10 mg/kg in the diabetic group and 30 mg/kg in the healthy controls. Chronic administration of CHEM (30 mg/kg twice daily) for a week in the diabetic group attenuated development of mechanical hypersensitivity. CONCLUSIONS: Reduction of pain-related behavior by a lower dose of the TRPA1 channel antagonist in the diabetic than in the control group suggests that endogenous compounds resulting from diabetes mellitus and acting on the TRPA1 channel contribute to diabetic hypersensitivity. Prolonged antihypersensitivity effect after chronic treatment suggests that daily administration of a TRPA1 channel antagonist may prevent development of diabetic hypersensitivity.

Differential effect of capsaicin treatment on pain-related behaviors after plantar incision.

UNLABELLED: We evaluated the effect of infiltration of dilute solutions of capsaicin, administered before plantar incision, on 3 pain-related behaviors: guarding pain, heat-withdrawal latency, and mechanical-withdrawal threshold. Perineural application of capsaicin was also studied and the appearance of the wound was also evaluated. Dilute solutions of capsaicin .025% and .10% were infiltrated in the plantar region 1 day before incision. In another group of rats, perineural capsaicin (1%) was applied to the nerves innervating the plantar aspect of the rat hindpaw. Rats were then tested for pain-related behaviors before and after plantar incision and then daily thereafter. Wound appearance was graded and histopathology was evaluated. Infiltration with capsaicin reduced guarding pain and heat hyperalgesia after plantar incision; there were minimal effects on mechanical responses. Perineural-capsaicin application produced a similar result. Both capsaicin infiltration and perineural-capsaicin application impaired wound apposition. Histologic evaluation also confirmed impaired wound apposition after capsaicin infiltration. In conclusion, dilute solutions of capsaicin have differential effects on pain-related behaviors after plantar incision. Based on the antinociception produced by capsaicin both via infiltration and perineural injection, the effect on wound appearance was likely related to its inhibitory effects on pain behaviors and was not necessarily a local effect of the drug. PERSPECTIVE: This study demonstrated that capsaicin infiltration before plantar incision produced an analgesic effect that depended upon the stimulus modality tested. When evaluating novel treatments for postoperative pain, studies using a single stimulus modality may overlook an analgesic effect by not examining a variety of stimuli.

Acute effect of an incision on mechanosensitive afferents in the plantar rat hindpaw.

The purpose of this study was to examine which primary afferent fibers are sensitized to mechanical stimuli after an experimental surgical incision to the glabrous skin of the rat hindpaw. Afferent fibers teased from the L(5) dorsal root or the tibial nerve were recorded in anesthetized rats. The mechanical response properties of each fiber were characterized before and 45 min after an incision (or sham procedure) within the mechanical receptive field. Sensitization is characterized by an expansion of the mechanical receptive field, an increase in background activity, an increase in response magnitude, or a decrease in response threshold. After incision, the background activity and response properties of Abeta-fibers (n = 9) to mechanical stimuli were unchanged. Four of 13 mechanosensitive Adelta-fibers exhibited sensitization after the incision; response threshold decreased, response magnitude increased, or receptive field size increased. Background activity of Adelta-fibers was not increased by the incision. Sensitization was observed in 4 of 18 mechanosensitive C-fibers 45 min after the incision. Background activity of C-fibers was not increased by the incision. In a group of mechanically insensitive afferent fibers (MIAs), 3 of 7 Adelta-fibers and 4 of 10 C-fibers sensitized 45 min after incision. Response threshold was decreased in only 2 of 17 MIAs; receptive field size increased in 7 of 17 MIAs. Abeta-fibers did not sensitize after the incision, and only 8 of 31 (26%) mechanosensitive Adelta- and C-fibers gave evidence of sensitization. In a group of MIA Adelta- and C-fibers, a greater percentage of 17 fibers studied (41%) were sensitized after incision. In this model, the principal effect of an incision, when examined 45 min after the insult, is an increase in receptive field size of the afferents, particularly those characterized as MIAs. To the extent that the mechanical hyperalgesia characterized in the same model is initiated in the periphery, it would appear that spatial summation of modestly increased response magnitude is important to the development of hyperalgesia.

Dissociation of the alpha 2-adrenergic antinociception from sedation following microinjection of medetomidine into the locus coeruleus in rats.

It is well established that alpha 2-adrenoceptor agonists have sedative and antinociceptive properties. In the current behavioral study we tried to find out if the alpha 2-adrenergic sedative and antinociceptive effects can be dissociated. We tested the hypothesis that alpha 2-adrenergic sedation is mediated by the locus coeruleus (LC) and antinociception by spinal alpha 2-adrenoceptors. Also, we addressed the possibility that intracerebral injection of an alpha 2-agonist might produce its antinociceptive effect by an action directly at the spinal cord. Medetomidine, an alpha 2-adrenergic agonist, or atipamezole, an alpha 2-adrenergic antagonist, were microinjected bilaterally into the LC through chronic cannulae in unanesthetized Han-Wistar rats. The effect on locomotor activity (/vigilance), tail-flick and hot-plate response, and on formalin-induced pain behavior was determined. Medetomidine microinjected into the LC (1-10 micrograms/cannula) produced dose-dependently hypolocomotion (/sedation), increase of response latencies in the hot-plate and the tail-flick tests, and a decrease in the formalin-induced pain behavior. Hypolocomotion (/sedation) was obtained at a lower medetomidine dose (1 microgram/cannula) than antinociception (3-10 micrograms/cannula). The lowest medetomidine dose used (1 microgram/cannula), which induced significant hypolocomotion (/sedation), produced either no antinociception (hot-plate and tail-flick tests) or even a slight hyperalgesia (formalin test). The hypolocomotion (/sedation) but not antinociception (tail-flick test) induced by systemic administration of medetomidine (100 micrograms/kg s.c.) could be reversed by atipamezole (10 micrograms/cannula) microinjected into the LC. Only a high systemic dose of atipamezole (1 mg/kg s.c.) reversed the antinociceptive effects of medetomidine.(ABSTRACT TRUNCATED AT 250 WORDS)