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Von Frey Hair (von + frey_hair)
Selected AbstractsA MOUSE MODEL FOR PERIPHERAL NEUROPATHY PRODUCED BY A PARTIAL INJURY OF THE NERVE SUPPLYING THE TAILJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 4 2002SK Back We attempted to develop a mouse model for peripheral neuropathy by a partial injury of the nerve supplying the tail. Under enflurane anesthesia, the unilateral superior caudal trunk was resected between the S3 and S4 spinal nerves. Tests for thermal allodynia were conducted by immersing the tail into 4 or 38°C water. The mechanical allodynia was assessed by stimulating the tail with a von Frey hair (1.96 mN, 0.2 g). After the nerve injury, the experimental animals had shorter tail withdrawal latencies to cold and warm water immersion than the presurgical latency, and exhibited an increase in tail response to von Frey stimulation. We interpret these abnormal sensitivities as the signs of mechanical, cold and warm allodynia following the superior caudal trunk injury in the mouse. [source] Decreased physical function and increased pain sensitivity in mice deficient for type IX collagenARTHRITIS & RHEUMATISM, Issue 9 2009Kyle D. Allen Objective In mice with Col9a1 gene inactivation (Col9a1,/,), osteoarthritis (OA) and intervertebral disc degeneration develop prematurely. The aim of this study was to investigate Col9a1,/, mice for functional and symptomatic changes that may be associated with these pathologies. Methods Col9a1,/, and wild-type mice were investigated for reflexes, functional impairment (beam walking, pole climbing, wire hang, grip strength), sensorimotor skills (rotarod), mechanical sensitivity (von Frey hair), and thermal sensitivity (hot plate/tail flick). Gait was also analyzed to determine velocity, stride frequency, symmetry, percentage stance time, stride length, and step width. Postmortem, sera obtained from the mice were analyzed for hyaluronan, and their knees and spines were graded histologically for degeneration. Results Col9a1,/, mice had compensatory gait changes, increased mechanical sensitivity, and impaired physical ability. Col9a1,/, mice ambulated with gaits characterized by increased percentage stance times and shorter stride lengths. These mice also had heightened mechanical sensitivity and were deficient in contact righting, wire hang, rotarod, and pole climbing tasks. Male Col9a1,/, mice had the highest mean serum hyaluronan levels and strong histologic evidence of cartilage erosion. Intervertebral disc degeneration was also detected, with Col9a1,/, mice having an increased incidence of disc tears. Conclusion These data describe a Col9a1,/, behavioral phenotype characterized by altered gait, increased mechanical sensitivity, and impaired function. These gait and functional differences suggest that Col9a1,/, mice select locomotive behaviors that limit joint loads. The nature and magnitude of behavioral changes were largest in male mice, which also had the greatest evidence of knee degeneration. These findings suggest that Col9a1,/, mice present behavioral changes consistent with anatomic signs of OA and intervertebral disc degeneration. [source] Neuronal disinhibition in the trigeminal nucleus caudalis in a model of chronic neuropathic painEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2010Yasmina B. Martin Abstract The mechanisms underlying neuropathic facial pain syndromes are incompletely understood. We used a unilateral chronic constriction injury of the rat infraorbital nerve (CCI-IoN) as a facial neuropathic model. Pain-related behavior of the CCI-IoN animals was tested at 8, 15 and 26 days after surgery (dps). The response threshold to mechanical stimulation with von Frey hairs on the injured side was reduced at 15 and 26 dps, indicating the presence of allodynia. We performed unitary recordings in the caudalis division of the spinal trigeminal nucleus (Sp5C) at 8 or 26 dps, and examined spontaneous activity and responses to mechanical and thermal stimulation of the vibrissal pad. Neurons were identified as wide dynamic range (WDR) or low-threshold mechanoreceptive (LTM) according to their response to tactile and/or noxious stimulation. Following CCI-IoN, WDR neurons, but not LTM neurons, increased their spontaneous activity at 8 and 26 dps, and both types of Sp5C neurons increased their responses to tactile stimuli. In addition, the on,off tactile response in neurons recorded after CCI-IoN was followed by afterdischarges that were not observed in control cases. Compared with controls, the response inhibition observed during paired-pulse stimulation was reduced after CCI-IoN. Immunohistochemical studies showed an overall decrease in GAD65 immunoreactivity in Sp5C at 26 dps, most marked in laminae I and II, suggesting that following CCI-IoN the inhibitory circuits in the sensory trigeminal nuclei are depressed. Consequently, our results strongly suggest that disinhibition of Sp5C neurons plays a relevant role in the appearance of allodynia after CCI-IoN. [source] Activity of corneal nociceptive nerve fibers during allergic challenge of the ocular surfaceACTA OPHTHALMOLOGICA, Issue 2009J GALLAR Purpose The aim of this work was to study in vitro the spontaneous and stimulus-evoked electrical activity of corneal nociceptive nerve fibers during acute allergic inflammation of the ocular surface induced in the guinea-pig. Methods Animals received i.p. 10% ovalbumin (OVA). 14 days later, a 10µl drop of OVA was applied topically to each eye. Blinking and scratching movements directed to the eye were measured during 10 min, and ocular symptoms (edema and hyperemia) and tear rate were measured. Animals were killed afterwards and both eyes were immediately excised and mounted in a superfused (32°C) recording chamber. Electrical activity of corneal sensory receptors was recorded from nerve filaments dissected from the ciliary nerves. Mechanical (calibrated von Frey hairs), thermal (bath solution temperature down to 20°C or up to 52°C), and chemical stimulation (30s-pulses of 98%CO2) were performed. Spontaneous (SA) and stimulus-evoked activity were analyzed. Results After the allergic challenge, eye-scratching behavior was present in 4 out of 15 animals and blinking movements increased from 1±0.05 to 26±5. Tearing also increased compared to control (33±3 vs. 5±1 mm). Compared to naive eyes, proportion of nociceptors with SA (17% vs. 5%) and spontaneous discharge rate (0.13±0.07 vs. 0.01±0.01 imp/s) were increased. Mechanical threshold of mechano-nociceptive units decreased significantly (0.37±0.05 vs. 0.89±0.13 mN). Chemosensitivity of polymodal nociceptors was slightly increased (1.87±0.42 vs. 1.34±0.23 imp/s). Conclusion Changes in corneal sensory nerve activity observed acutely after allergic challenge of the eye surface may constitute the basis of itching and discomfort sensations, and hypersensitivity observed in allergic patients. [source] | ||||||||||