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Differential Effects Of Duloxetine On Two Separate Behaviors In The Rat Formalin Model
Author(s) -
Knittle Desiree,
Jett MaryFrances,
Ford Anthony,
Nunn Philip,
Zhong Yu
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a776-b
Subject(s) - licking , duloxetine , biting , anesthesia , morphine , chemistry , medicine , pharmacology , biology , alternative medicine , pathology , ecology
The present study examined the analgesic effects of duloxetine (a serotonin‐noradrenaline reuptake inhibitor) and morphine (an opioid) on the licking/biting and flinching behaviors in the rat formalin test, a pre‐clinical model of central sensitization. Adult male Sprague‐Dawley rats were dosed with duloxetine, morphine or vehicle subcutaneously (s.c.) prior to intraplantar injection of formalin (5%, 50μl). The rats were then immediately placed into a Plexiglas observation chamber. Duration of licking/biting and flinching were recorded in 5 min bins for 60 min. Cumulative activities in phase I (0–5 min), early (10–40 min) and late (40–60 min) phase II were analyzed using Student’s t‐test. Duloxetine (10 or 30 mg/kg) dosed 120 minutes before formalin produced dose‐dependent suppression of licking/biting behavior in early phase II with a corresponding dose‐related augmentation of flinching behavior in late phase II. We also compared the effect of duloxetine when administered at different time points prior to formalin. Giving duloxetine (10 mg/kg) at 70 minutes prior to formalin injection produced maximal suppression of licking/biting behavior (early phase II) and maximal enhancement of flinching behavior (late phase II). In contrast, morphine (2 mg/kg, 15 min prior) produced similar and significant suppression of the peak licking/biting and flinching behaviors. Licking/biting and/or flinching behaviors have been commonly used to represent the nocifensive response in the formalin model. However, the differential effect of duloxetine on these behaviors highlights the possible different neural circuits underlying them.