title: A small, silent, low friction, linear actuator for mechanical nociceptive testing in veterinary research.
abstract: Air pressure is commonly used to drive a mechanical stimulus for nociceptive threshold testing. This may be bulky, noisy, non-linear and suffer from friction, hence development of a better system is described. A novel, light (14 g) rolling diaphragm actuator was constructed, which supplied 20 N force via a constant actuation area irrespective of the pressure and position in the stroke. Three round-ended pins, 2.5 mm diameter, mounted in a triangle on the piston, provided the stimulus. Pressure was increased manually using a syringe with the rate of rise of force controlled at 0.8 N/s by warning lights. The pressure/force relationship was calibrated using a static force transducer and mercury column. Data were collected with the actuator attached to the antero-medial radius of 12 cats and four dogs. Mechanical threshold was recorded when the animal withdrew the limb and/or turned towards the actuator. Safety cut-off was 20 N. The pressure/force relationship was linear and independent of the start point in the actuator stroke. Baseline feline thresholds were 10.0 +/- 2.5 N (mean +/- SD), which increased significantly 30 min after butorphanol administration. Baseline canine thresholds were 5.5 +/- 1.4 N and increased significantly between 15 and 45 min after administration of fentanyl or butorphanol. The system overcame the problems of earlier devices and detected an opioid-induced increase in threshold. It has considerable advantages over previous systems for research in analgesia.
authors.affiliation: Topcat Metrology, Ely, Cambridgeshire, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Dixon
authors.forename: P M
authors.initials: PM
authors.lastname: Taylor
authors.forename: L
authors.initials: L
authors.lastname: Slingsby
authors.forename: M V
authors.initials: MV
authors.lastname: Hoffmann
authors.forename: S B R
authors.initials: SB
authors.lastname: Kästner
authors.forename: J
authors.initials: J
authors.lastname: Murrell
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D002077:Butorphanol / Q000494:pharmacology; D002415:Cats; D004285:Dogs; D005260:Female; D005283:Fentanyl / Q000494:pharmacology; D008297:Male; D010146:Pain / Q000503:physiopathology / Q000517:prevention & control / Q000662:veterinary*; D010147:Pain Measurement / Q000295:instrumentation / Q000662:veterinary*; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology*; D011312:Pressure; D013314:Stress, Mechanical; D014730:Veterinary Medicine / Q000295:instrumentation* / Q000379:methods
chemical_list: D000700:Analgesics; D002077:Butorphanol; D005283:Fentanyl