Calibrated Forceps: A Useful Tool to Study Mechanical Nociception

摘要

This piece discusses mechanical stimulators currently available to researchers, noting both their merits and shortcomings. If used properly and in combination with von Frey-iike filaments, calibrated forceps can be very helpful and can provide a broad range of mechanical stimuli suitable for studying a wide variety of tissues.There are 2 types of handheld von Frey-like mechanical stimulators, one with a bendable probe and one with a rigid probe. Semmes Weinstein von Frey-like nylon monofilaments are bendable and have served our research community well for more than 50 years.10 They provide high accuracy in the innocuous range in which bowing of the filament limits the maximum force applied. However, they produce less desirable results in the noxious range; probe diameter increases as stimulus intensity is increased (probes with high bending forces can produce ambiguous results because of complex features of a hind paw, for example), can be shifted by the probe, and adequate control for stimulus onset and termination is absent. Alternatively, the rigid probe type of von Frey-like mechanical stimulator is basically a variation of a dynamometer that can be easily mated with strain gauges to monitor force via a Wheatstone bridge circuit. There are several commercially available rigid probe mechanical stimulators, including electronic von Frey-like devices with a single strain gauge (Bioseb: Electronic von Frey; IITC: ElectrovonFrey and 2600 Digital Paw Pressure Applicator; Somedic AB: Electronic von Frey).