A Central Amygdala Input to the Parafascicular Nucleus Controls Comorbid Pain in Depression

Abstract

Summary: While comorbid pain in depression (CP) occurs at a high rate worldwide, the neural connections underlying the core symptoms of CP have yet to be elucidated. Here, we define a pathway whereby GABAergic neurons from the central nucleus of the amygdala (GABACeA) project to glutamatergic neurons in the parafascicular nucleus (GluPF). These GluPF neurons relay directly to neurons in the second somatosensory cortex (S2), a well-known area involved in pain signal processing. Enhanced inhibition of the GABACeA→GluPF→S2 pathway is found in mice exhibiting CP symptoms. Reversing this pathway using chemogenetic or optogenetic approaches alleviates CP symptoms. Together, the current study demonstrates the putative importance of the GABACeA→GluPF→S2 pathway in controlling at least some aspects of CP. : Zhu et al. identify that GABAergic neurons from the central nucleus of the amygdala (GABACeA) project to glutamate neurons in the parafascicular nucleus (GluPF) and uncover the role of this pathway in regulation of pain symptoms in depression via connecting with the second somatosensory cortex. Keywords: comorbid pain, central nucleus of the amygdala, parafascicular nucleus, second somatosensory cortex, neural circuits, optogenetics, chemogenetics, retrograde trans-monosynaptic tracing, GABA neurons, glutamate neurons