CNS animal fMRI in pain and analgesia

Abstract

Animal imaging of brain systems offers exciting opportunities to better understand the neurobiology of pain and analgesia. Overall functional studies have lagged behind human studies as a result of technical issues including the use of anesthesia. Now that many of these issues have been overcome including the possibility of imaging awake animals, there are new opportunities to study whole brain systems neurobiology of acute and chronic pain as well as analgesic effects on brain systems de novo (using pharmacological MRI) or testing in animal models of pain. Understanding brain networks in these areas may provide new insights into translational science, and use neural networks as a "language of translation" between preclinical to clinical models. In this review we evaluate the role of functional and anatomical imaging in furthering our understanding in pain and analgesia.

Dissociable Effects of the Cannabinoid Receptor Agonists Δ9-Tetrahydrocannabinol and CP55940 on Pain-Stimulated Versus Pain-Depressed Behavior in Rats

“…For example, noxious stimuli activate both serial and parallel spinal and supraspinal pathways, and different neural circuits have been associated with different components of pain (sensory versus affective components of pain) (Price, 2002;Borsook and Becerra, 2011). Results of the present study suggest that THC and other cannabinoids may be more effective in modulating neural circuits that mediate acid-induced stimulation of stretching than those mediating acid-induced depression of ICSS.…”

[18F]-fluorodeoxyglucose positron emission tomography of the cat brain: A feasibility study to investigate osteoarthritis-associated pain

“…brain metabolism in the above three brain regions is in agreement with the brain plasticity described during chronic pain in animals. Indeed, an increase in brain activity has already been described in several brain regions in rodents including PAG, amygdala, thalamus, primary somatosensory cortex, secondary somatosensory cortex, and anterior cingulate cortex (Borsook and Becerra, 2011;Thompson and Bushnell, 2012).…”

“…Unfortunately, we were not able to assess the amygdale, as this small brain region was too difficult to delineate adequately with the brain atlas used as reference (Reinoso-Suarez, 1961). Usually, an isolated imaging study is not sufficient to discover all brain activity changes because of the high individual variability (Borsook et al, 2010;Borsook and Becerra, 2011;Thompson and Bushnell, 2012). Thus, other studies will be needed to determine all the brain changes related to OA-associated pain in cats.…”

“…The use of functional imaging of the CNS to assess pain in animals is a recent and growing field (Borsook and Becerra, 2011). The major advantages of these techniques are the possibility to collect objective measures of pain, to compare data across several species, to target specific central mechanisms, and to perform study designs with repeated data (Borsook et al, 2010;Borsook and Becerra, 2011;Davis and Moayedi, 2013).…”

Lost but making progress—Where will new analgesic drugs come from?

“…Brain imaging itself is a promising biomarker for chronic pain (144, 145) because it can track functional and morphological changes in multiple brain systems that can be related to the pain condition in animals and humans (135, 153–155). Recent work has begun to define a neural signature of experimental pain in human subjects (156).…”