Optogenetic characterization of Corticotropin-releasing factor neurons of Barrington's Nucleus

Georgetown University, Washington DC

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Abstract

? DESCRIPTION (provided by applicant): This proposal focus on the cellular properties of neurons of Barrington's nucleus (BRN) and their responses to afferent or pharmacological stimulation. BRN neurons are positioned to coordinate micturition with arousal and voiding behaviors as they innervate the preganglionic neurons that regulate detrusor contraction as well as the locus coeruleus (LC), the major brain norepinephrine nucleus. Dysfunctions in this circuit may also underlie bladder and voiding disorders, particularly Underactive Bladder (UAB). We will take advantage of technical advances combining genetics, optical stimulation and imaging to elucidate how this nucleus functions and how it can be manipulated to treat disorders such as UAB. As the majority of BRN neurons express the stress related neuropeptide, corticotropin-releasing factor (CRF), they can be easily identified and studied in brain slices from mice with CRF-Cre dependent expression of fluorescence reporter proteins. The close proximity of the LC and BRN in these slices we will allow us to directly quantify the relationship between BRN and LC neurons and to better understand this central branch of the micturition reflex. In aim one we will characterize with patch clamp recordings the cellular properties of neurons in the BRN-LC circuit and how they change with aging. This will be paired with immunocytochemical (IHC) determination of neurotransmitter phenotype. We hypothesize that the majority of BRN neurons co-localize CRF and glutamate. Then we will use CRF- Channelrhodopsin 2 mice to control CRF expressing BRN neurons with different frequencies of optical stimulation and quantify their synaptic action in the LC. In aim two using CRF-GCaMP6f mice that express a Ca2+ indicator in CRF neurons we will be able to investigate the functional BRN circuitry as it modifies with age and thus identify cellular changes in the pontine micturition center that may be causal to age-related UAB. Our exploratory proposal will provide us with the conceptual framework and essential preliminary data to develop a mechanistic knowledge of the functional and pharmacological regulation of the BRN circuitry relevant for the diagnosis, evaluation, and treatment of UAB. The goal of the application is to set the stage for a combined in vitro and in vivo approach to the understanding of the role of the pontine micturition center in UAB.