Insular serotonin modulatesbehavioral responses to danger

Proposal Summary The long-term goal of this research training plan is to enhance our understanding of the neurobiology underlying

behavioral responses to danger signals and provide translatable findings that will contribute to the development of novel therapeutics and treatments for anxiety-related disorders. This research proposal was crafted to build a foundation for becoming a fully independent scientist through developing technical expertise in systems neuroscience techniques,

increasing my knowledge base, learning programming and data analysis skills, and refining my professional development

skills. Boston College was selected as the environment for me to carry out this proposal and achieve my training goals due

to its accessible and expert behavioral neuroscience faculty, wide range of available techniques and equipment, and access to the large neuroscience network within the greater Boston area. The research objective is to identify and describe a dorsal raphe nucleus (DRN) to insula tract responsible for responding to danger signals and executing appropriate

behavioral responses in males and females. Hyperactivity of the DRN and effects of 5-HT released in the forebrain are closely related to anxiety-related behaviors. Similarly, the insula integrates interoceptive and exteroceptive cues and contributes to motivated behaviors that are influenced by anxiety. Although both the DRN and insula have been

implicated separately in anxiety-related behaviors, it is not yet known how 5-HT influences this system. The aims of this proposal are designed to describe how insular 5-HT modulates the appropriate behavioral responses to danger signals. Aim 1 will utilize a viral-genetic anterograde tracing method to describe and compare insular DRN projections and

serotonergic receptors colocalizations between insular rostral-caudal subregions, insular subregions, and laminar layers. It

is expected that DRN projections will target both inhibitory and excitatory neurons in all insula subregions and colocalize

on 5-HT2C receptors expressing neurons in the insula. Aim 2 will next seek to visualize insular serotonergic activity in response to a social and directly experienced danger cue using GRAB5-HT, a sensor for 5-HT activity, and in vivo fiber

photometry. It is expected that there will be greater insular 5-HT activity in response to a stressed conspecific and danger cue than a naive conspecific and safety cue, respectively. Finally, Aim 3 uses a chemogenetic approach to inhibit or stimulate insula-projecting DRN neurons to determine if the DRN-insula tract is necessary and sufficient for the

appropriate behavioral response to a social and directly experienced danger cue. Inhibiting the DRN-insula tract should

increase sociability while decreasing fear, while stimulating the DRN-insula tract should trigger 5-HT release, therefore

decreasing sociability but increasing fear. Completion of these three complementary aims will result in the most thorough

understanding of this circuitry’s composition and function in response to danger signals to date and inform development of more effective treatments for anxiety-related disorders.