title: Simultaneous absolute measures of glabrous skin hemodynamic and light-scattering change in response to formalin injection in rats.
abstract: Subcutaneous injection of formalin is a well-known model to study the nature of inflammatory pain. One of the cardinal signs of inflammation is redness, as a result of increased blood perfusion. We used an optical technology, light reflectance spectroscopy, to noninvasively obtain absolute measures of cutaneous hemodynamic components, including the concentrations of oxy- ([HbO]), deoxy- ([Hb]), total-hemoglobin ([HbT]), oxygen saturation (SO(2)), and the reduced light-scattering coefficient (μs'). The objective is to assess the effect of formalin-induced skin inflammation on the aforementioned parameters. Six rats were injected with formalin (50 μl, 3%) into left hind paw under pentobarbital anesthesia. Our results indicate prolonged increases in [HbO], [HbT], and SO(2) post injection only in the ipsilateral side. No statistically significant changes in [Hb] and μ(s)' occurred in either side. The arterial blood influx tends to be the major attribute of local hyperemia during inflammation. Thereby, [HbO] appears to be superior to [Hb] in measuring inflammation. In conclusion, the needle-probe-based light reflectance can be a feasible means to obtaining absolute measures of skin hemodynamic and light-scattering parameters when studying inflammatory pain.
authors.affiliation: Department of Psychology, College of Science, University of Texas at Arlington, Arlington, TX 76019-0528, USA.
authors.forename: Ji-Wei
authors.initials: JW
authors.lastname: He
authors.forename: Dheerendra
authors.initials: D
authors.lastname: Kashyap
authors.forename: Lara A
authors.initials: LA
authors.lastname: Trevino
authors.forename: Hanli
authors.initials: H
authors.lastname: Liu
authors.forename: Yuan Bo
authors.initials: YB
authors.lastname: Peng
mesh_terms: D000818:Animals; D005557:Formaldehyde / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects*; D006454:Hemoglobins / Q000378:metabolism; D008027:Light; D008297:Male; D010100:Oxygen / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D012867:Skin / Q000098:blood supply* / Q000187:drug effects; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D006454:Hemoglobins; D005557:Formaldehyde; D010100:Oxygen