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Type: Journal article
Title: Low formalin concentrations induce fine-tuned responses that are sex and age-dependent: A developmental study
Author: Zoukir, I.
Tadros, M.
Clifton, V.
Beagley, K.
Hodgson, D.
Citation: PLoS One, 2013; 8(1):1-10
Publisher: Public Library of Science
Issue Date: 2013
ISSN: 1932-6203
Statement of
Ihssane Zouikr, Melissa A. Tadros, Vicki L. Clifton, Kenneth W. Beagley, Deborah M. Hodgson
Abstract: The formalin test is increasingly applied as a model of inflammatory pain using high formalin concentrations (5–15%). However, little is known about the effects of low formalin concentrations on related behavioural responses. To examine this, rat pups were subjected to various concentrations of formalin at four developmental stages: 7, 13, 22, and 82 days of age. At postnatal day (PND) 7, sex differences in flinching but not licking responses were observed with 0.5% formalin evoking higher flinching in males than in females. A dose response was evident in that 0.5% formalin also produced higher licking responses compared to 0.3% or 0.4% formalin. At PND 13, a concentration of 0.8% formalin evoked a biphasic response. At PND 22, a concentration of 1.1% evoked higher flinching and licking responses during the late phase (10–30 min) in both males and females. During the early phase (0–5 min), 1.1% evoked higher licking responses compared to 0.9% or 1% formalin. 1.1% formalin produced a biphasic response that was not evident with 0.9 or 1%. At PND 82, rats displayed a biphasic pattern in response to three formalin concentrations (1.25%, 1.75% and 2.25%) with the presence of an interphase for both 1.75% and 2.25% but not for 1.25%. These data suggest that low formalin concentrations induce fine-tuned responses that are not apparent with the high formalin concentration commonly used in the formalin test. These data also show that the developing nociceptive system is very sensitive to subtle changes in formalin concentrations.
Keywords: Animals; Animals, Newborn; Rats; Rats, Wistar; Pain; Formaldehyde; Pain Measurement; Injections, Subcutaneous; Behavior, Animal; Age Factors; Sex Factors; Dose-Response Relationship, Drug; Time Factors; Female; Male; Nociception
Rights: © 2013 Zouikr et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
RMID: 0020124641
DOI: 10.1371/journal.pone.0053384
Appears in Collections:Obstetrics and Gynaecology publications

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