title: Development and validation of an automated system for detection and assessment of scratching in the rodent.
abstract: Pruritus, the sensation of itch, which evokes reflex scratching behavior, has a diverse etiology. Because of its clinical significance, mechanisms of pruriception are an important topic. In the present work we describe and validate a paw motion detector (PMD) system. The system employs a small removable metal band placed on one hind paw that provides a signal indicative of paw movement through perturbation of an electromagnetic (EM) field. C57Bl/6 mice were fitted with a unilateral hind paw band and adapted to testing cylinders equipped with EM signal emission and detection. The following observations were made: (1) in mice, unilateral SQ injection of 48/80 into the dorsolateral aspect of the neck evoked periodic high frequency bursts of scratching at the injected site with the ipsilateral (banded) but not the contralateral (not banded) hind paw. (2) Cross correlation between PMD and human observer counts after SQ 48/80 using the specified computational algorithm revealed a highly significant correlation. (3) SQ histamine and 48/80 over a 1hour interval produced dose dependent scratching, which diphenhydramine dose dependently reversed. Chloroquine scratching displayed an inverse u-shaped dose response curve, which was insensitive to diphenhydramine. (4) SQ 48/80 at intervals over 28 days showed no change in the scratching response within the same cohort of mice. (5) Power analysis showed 40% changes in scratching activity could be detected at the p<0.05 level with groups of 4 mice. These observations indicate that the system described can efficiently define the actions and pharmacology of pruritogenic agents.
authors.affiliation: Department of Anesthesiology, University of California, San Diego, 9500 Gilman Drive-CTF C-312, La Jolla, CA 92093-0818, USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Marino
authors.forename: Polly
authors.initials: P
authors.lastname: Huang
authors.forename: Shelle
authors.initials: S
authors.lastname: Malkmus
authors.forename: Erin
authors.initials: E
authors.lastname: Robertshaw
authors.forename: Elaine A
authors.initials: EA
authors.lastname: Mac
authors.forename: Yuri
authors.initials: Y
authors.lastname: Shatterman
authors.forename: Tony L
authors.initials: TL
authors.lastname: Yaksh
mesh_terms: D000465:Algorithms; D000703:Analog-Digital Conversion; D000818:Animals; D018926:Anti-Allergic Agents / Q000627:therapeutic use; D001331:Automation; D001522:Behavior, Animal / Q000502:physiology*; D002738:Chloroquine; D003627:Data Interpretation, Statistical; D004155:Diphenhydramine / Q000627:therapeutic use; D004574:Electromagnetic Fields; D005528:Foot; D006632:Histamine; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009038:Motion; D011537:Pruritus / Q000139:chemically induced / Q000188:drug therapy / Q000523:psychology; D011589:Psychology, Experimental / Q000295:instrumentation*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D018926:Anti-Allergic Agents; D003189:p-Methoxy-N-methylphenethylamine; D006632:Histamine; D002738:Chloroquine; D004155:Diphenhydramine