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Rat ultrasonic vocalizations as a measure of the emotional component of chronic pain

Burgdorf, Jeffrey S.a,,b; Ghoreishi-Haack, Nayerehb; Cearley, Cassia N.b; Kroes, Roger A.a,,b; Moskal, Joseph R.a,,b

doi: 10.1097/WNR.0000000000001282
Integrative Systems
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In humans, chronic pain is often expressed as a spontaneous emotional response which can lead to fragmented sleep. Rat 50-kHz and 20-kHz ultrasonic vocalizations are well-established measures of positive and negative emotional states, respectively. The rat chronic constriction injury model was used to induce chronic pain, and ultrasonic vocalizations were measured in both the heterospecific rough-and-tumble play (i.e. tickling) test as well as during 24-hour home cage recordings. Rates of hedonic 50-kHz ultrasonic vocalizations during the non-stimulus periods of the tickling test, as well as the rewarding value of tickling, were reduced in chronic constriction injury rats compared to sham controls. In the 24-hour home cage recording study, chronic constriction injury animals showed a reduced amplitude in circadian activity, as well as reduced hedonic 50-kHz ultrasonic vocalizations and increased evoked and spontaneous aversive 20-kHz ultrasonic vocalizations. These data demonstrate that rat ultrasonic vocalizations can be used to capture core symptoms of chronic pain and may be useful in the elucidation of the neuronal mechanisms that underlie the affective component of pain.

aFalk Center for Molecular Therapeutics, Department of Biomedical Engineering, Northwestern University

bAptinyx Inc., Evanston, Illinois, USA

Received 14 May 2019 Accepted 24 May 2019

Correspondence to Jeffrey S. Burgdorf, Falk Center for Molecular Therapeutics, Department of Biomedical Engineering, Northwestern University, 1801 Maple Ave, Suite 4300, Evanston, IL 60201, USA, Tel: +(847) 491 4872; fax: +(847) 491 4810; e-mail: j-burgdorf@northwestern.edu

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