title: Low dose aspirin attenuates escape/avoidance behavior, but does not reduce mechanical hyperalgesia in a rodent model of inflammatory pain.
abstract: The present experiment examined the effect of aspirin on the escape/avoidance behavioral response to a mechanical stimulus (476 mN von Frey monofilament) in the place escape avoidance paradigm (PEAP) following subcutaneous administration of carrageenan (CARR). Forty-one male Sprague-Dawley rats received subcutaneous injection of CARR or saline in the left hindpaw and 3 1/2 h later were administered aspirin (0, 50 or 150 mg/kg). Thirty minutes later, animals were tested in the PEAP and then the mechanical paw withdrawal threshold was measured. Compared with Saline vehicle-treated controls, all CARR-treated animals displayed hyperalgesia, as reflected by enhanced responding to mechanical stimulation applied to the CARR-injected paw. Mechanical hyperalgesia was significantly reduced by the pre-treatment of 150 mg/kg, but not 50 mg/kg aspirin. In the PEAP, CARR vehicle-treated animals avoided a preferred location of the test chamber that was associated with mechanical stimulation of the hyperalgesic paw. The shift from a preferred dark side of the chamber to the light side was attenuated by pre-treatment with both doses of aspirin (50 and 150 mg/kg). The lack of anti-hyperalgesia and avoidance behavior with 50 mg/kg aspirin suggests a decrease in the aversive nature of mechanical stimulation of the afflicted paw. It is suggested that the mechanisms underlying the affective/motivational dimension of nociception (escape/avoidance) can be dissociated from the processing of nociceptive information related to withdrawal responding.
authors.affiliation: Department of Psychology, Box 19528, University of Texas at Arlington, Arlington, TX 76019, USA. cjlabuda@yahoo.com
authors.forename: C J
authors.initials: CJ
authors.lastname: LaBuda
authors.forename: P N
authors.initials: PN
authors.lastname: Fuchs
mesh_terms: D000818:Animals; D001241:Aspirin / Q000008:administration & dosage* / Q000494:pharmacology; D001362:Avoidance Learning / Q000187:drug effects*; D002351:Carrageenan / Q000008:administration & dosage; D004305:Dose-Response Relationship, Drug; D004924:Escape Reaction / Q000187:drug effects*; D006614:Hindlimb; D006930:Hyperalgesia / Q000503:physiopathology*; D007249:Inflammation / Q000139:chemically induced / Q000503:physiopathology*; D007279:Injections, Subcutaneous; D008297:Male; D010146:Pain / Q000503:physiopathology; D010812:Physical Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values
chemical_list: D002351:Carrageenan; D001241:Aspirin