Inflammatory pain modifies dopaminergic functioning in the anterior cingulate cortex in mice
There is clinical evidence that neuronal signaling mediated by the neurotransmitter dopamine is altered in individuals with certain types of chronic pain such as fibromyalgia and chronic back pain. Dopaminergic signaling is of particular interest in the anterior cingulate cortex (ACC), a brain region involved in nociceptive processing, where its modulation has been shown to alleviate the affective and sensory components of pain in rodents. To better understand how dopamine modifies neuronal communication at synapses during pain states, UTCSP member Dr. Loren Martin and colleagues measured electrical properties of ACC neurons in a commonly used mouse model of inflammatory pain.
After injecting complete Freund’s Adjuvant (CFA) into the hind paws of mice, the authors first confirmed that the mice developed hypersensitivity to mechanical stimuli and signs of pain-related anxiety using behavioural assays. Brain slices were then collected from mice 3- or 4-days post-CFA injection, and synaptic responses were recorded from individual ACC neurons. The authors found that applying dopamine to the slices reduced synaptic responses in naïve mice but not in CFA-injected mice, 4 days post-treatment, suggesting that inflammation may affect neuronal communication through dopaminergic mechanisms. Additionally, the authors found that levels of endogenous dopamine were reduced in the ACC 3 days after CFA injection, which correlated with the onset of transient anxiety.
The results of this study, published in Neuroscience, point to altered neuronal signaling in the ACC during inflammatory pain. Specifically, the authors suggest that CFA may induce a dopamine deficit that correlates with pain and comorbid anxiety. This study provokes further questions about how chronic pain affects dopaminergic signaling in the ACC, which could ultimately lead to the development of new drugs to supplement current pain therapies.
Read more here:
Darvish-Ghane, S., Lyver, B., Facciol, A., Chatterjee, D., & Martin, L. J. (2022). Inflammatory pain alters dopaminergic modulation of excitatory synapses in the anterior cingulate cortex of mice. Neuroscience.
Written by: Quinn Pauli
Edited by: Georgia Hadjis