Intense focused ultrasound as a potential research tool for the quantification of diurnal inflammatory pain

Josephine D. Garcia, Michael Gofeld, P. Ray Illian, John D. Loeser, Michel Kliot, Abbi M. McClintic, Alice Ward, Anning Yao, Pierre D. Mourad*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Quantifying pain through assay of a human's or animal's response to a known stimulus as a function of time of day is a critical means of advancing chronotherapeutic pain management. Current methods for quantifying pain, even in the context of etiologies involving deep tissue, generally involve stimulation by quantifiable means of either cutaneous (heat-lamp tests, electrical stimuli) or both cutaneous and subcutaneous tissue (von Frey hairs, tourniquets, etc.) or study of proxies for pain (such as stress, via assay of cortisol levels). In this study, we evaluate the usefulness of intense focused ultrasound (iFU), already shown to generate sensations and other biological effects deep to the skin, as a means of quantifying deep diurnal pain using a standard animal model of inflammation. Beginning 5 days after injection of Complete Freund's Adjuvant into the plantar surface of the rat's right hind paw to induce inflammation, the rats were divided into two groups, the light-phase test group (09:00-18:00 h) and the dark-phase test group (23:00-06:00 h), both of which underwent iFU application deep to the skin. We used two classes of iFU protocol, motivated by the extant literature. One consisted of a single pulse (SP) lasting 0.375 s. The other, a multiple pulse (MP) protocol, consisted of multiple iFU pulses each of length 0.075 s spaced 0.075 s apart. We found the night group's threshold for reliable paw withdrawal to be significantly higher than that of the day group as assayed by each iFU protocol. These results are consistent with the observation that the response to mechanical stimuli by humans and rodents display diurnal variations, as well as the ability of iFU to generate sensations via mechanical stimulation. Since iFU can provide a consistent method to quantify pain from deep, inflamed tissue, it may represent a useful adjunct to those studying diurnal pain associated with deep tissue as well as chronotherapeutics targeting that pain.

Original languageEnglish (US)
Pages (from-to)84-89
Number of pages6
Issue number1
StatePublished - Jan 2013
Externally publishedYes


  • Diurnal
  • Inflammatory pain
  • Intense focused ultrasound
  • Rat

ASJC Scopus subject areas

  • Acoustics and Ultrasonics


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