An automated flinch detecting system for use in the formalin nociceptive bioassay.
The biphasic display of paw-flinch behavior in the rat after injection of formalin into the dorsum of the hind paw is used for the screening of anti-hyperalgesic agents. Described and characterized here is a less labor-intensive system for counting flinch activity by detecting movement of a small metal band placed on the formalin-injected paw. A signal is generated as the band breaks the electromagnetic field of a loop antenna located under the rat and processed through an algorithm that determines flinch activity using 1) amplitude, 2) zero-voltage crossing, and 3) signal duration. Flinches are summed and stored over a selected collection interval throughout the assay for later analysis. Studies have validated the measures with respect to 1) system stability over time; 2) system-to-"practiced observer" correlation on flinch detection, r2 = 0.94; 3) system variables including time of day, sex, age, and body weight; and 4) 50% effective dose values similar to those previously reported for intrathecal morphine and the NMDA antagonist MK-801.
Yaksh
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Department of Anesthesiology, University of California, San Diego, La Jolla, California 92093, USA. tyaksh@ucsd.edu
Ozaki
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McCumber
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Rathbun
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Svensson
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Malkmus
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Yaksh
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D000700:Analgesics / Q000494:pharmacology; D000818:Animals; D001331:Automation; D001522:Behavior, Animal / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D003625:Data Collection; D004305:Dose-Response Relationship, Drug; D004574:Electromagnetic Fields; D004576:Electromyography; D005260:Female; D005557:Formaldehyde; D007267:Injections; D007278:Injections, Spinal; D008297:Male; D008954:Models, Biological; D010147:Pain Measurement / Q000295:instrumentation*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012815:Signal Processing, Computer-Assisted
D000700:Analgesics; D005557:Formaldehyde