Biology subjects

Saab, B. J.

Publications and source records attributed to Saab, B. J..

2 recordsLinked to original sources

bioRxiv2020

Whole-Brain Longitudinal Profiling of Serotonergic Reuptake Inhibition

The serotonergic system is widely implicated in affect regulation, and a common target for psychopharmacological interventions. Selective Serotonin Reuptake Inhibitors (SSRIs) are the foremost drug class for treating depression, as well as anxiety, phobia and other affective disorders. However, the functional mechanisms determining SSRI efficacy remain elusive, hindering the targeted further development of serotonergic system interventions. Assays for longitudinal whole-brain interrogation of the serotonergic system are unavailable, yet such techniques are essential for identifying differential intervention effects across projection areas. We present a novel longitudinal opto-fMRI assay suitable for imaging longitudinal drug treatment effects on the mouse serotonergic system -- within-subject and with sub-millimetre spatial resolution. We apply this assay to a longitudinal fluoxetine treatment, and document reliable segmentation of brain-wide treatment effects, including identification of a brainstem cluster with a highly significant longitudinal trajectory, constituting a novel neurophenotype for psychopharmacological interventions. We differentiate serotonergic neuron activation from projection area activation, and offer brain-wide fMRI evidence for the prominent autoinhibition down-regulation theory of SSRI effects. Further, we show that given the sensitivity of the assay, SSRI treatment produces no persistent effects after treatment cessation in healthy subjects.

neuroscience↗

bioRxiv2020

A Whole-Brain Map and Assay Parameter Analysis of Mouse VTA Dopaminergic Activation

Ascending dopaminergic projections from neurons located in the Ventral Tegmental Area (VTA) are key to the etiology, dysfunction, and control of motivation, learning, and addiction. Due to evolutionary conservation of this nucleus and the extensive use of mice as disease models, establishing an assay for VTA dopaminergic signalling in the mouse brain is crucial for the translational investigation of motivational control as well as of neuronal function phenotypes for diseases and interventions. In this article we use optogenetic stimulation directed at VTA dopaminergic neurons in combination with functional Magnetic Resonance Imaging (fMRI), a method widely used in human deep brain imaging. We present a comprehensive assay producing the first whole-brain opto-fMRI map of dopaminergic activation in the mouse, and show that VTA dopaminergic system function is consistent with its structural VTA projections, diverging only in a few key aspects. While the activation map predominantly highlights target areas according to their relative projection densities (e.g. strong activation of the nucleus accumbens and low activation of the hippocampus), it also includes areas for which a structural connection is not well established (such as the dorsomedial striatum). We further detail the variability of the assay with regard to multiple experimental parameters, including stimulation protocol and implant position, and provide evidence-based recommendations for assay reuse, publishing both reference results and a reference analysis workflow implementation.

neuroscience↗