Chronic itch accompanies many skin diseases as well as systemic diseases and significantly decreases patients' quality of life. The majority of patients with chronic itch complain of aversive components of itch such as anxiety that are thought to be triggers or enhancers of itch. In this application, we will investigate the neuronal circuit of affective itch. In our preliminary data, we have confirmed activation of the neuronal circuit for anxiety (e.g., lateral parabrachial nucleus (LPB), amygdala, midcingulate cortex (MCC), and medial prefrontal cortex (mPFC)) following intradermal injection of pruritogens in mice.
Aim 1 will characterize anatomical and physiological properties of itch-signaling amygdala neurons using immunohistochemistry as well as in vivo single unit recording.
Aim 2 will investigate whether the projections from the LPB to the central nucleus of the amygdala and from the mPFC and MCC to the basolateral amygdala modulate itch and anxiety. Behavioral and electrophysiological properties of these amygdala neurons will be determined during optogenetic activation of somata of these projections.
Aim 3 will evaluate whether optogenetic inhibition of itch-signaling amygdala neurons can recover itch and anxiety in a mouse model of chronic itch. This novel approach would give us important information about the role of the affective itch circuit in chronic itch and whether treatments that target the circuit could improve both itch and anxiety in chronic itch patients.
Chronic itch is a significant clinical problem that is poorly treated. Patients with chronic itch often display high levels of anxiety, and anxiety is thought to be a trigger or aggravating factor for itch in these patients. This project will investigate the neuronal circuit of affective itch and thereby provide a novel therapeutic strategy for chronic itch.