Challenges in modeling the neural control of LUT

1. Overview The lower urinary tract (LUT) in mammals consists of the urinary bladder, external urethral sphincter (EUS) and the urethra. Control of the LUT is achieved via a neural circuit which integrates two distinct components. One component of the neural circuit is ‘reflexive’ in that it relies solely on input from sensory neurons in the bladder and urethra that is fed back via spinal neurons to the LUT. The second neural component is termed ‘top-down’ and is a conditioned input that comes from structures such as Pontine Micturition center (PMC), and Pontine storage center (PSC), that also receive the afferent sensory input from the LUT relayed through periaqueductal gray (PAG). The reader is referred to excellent references such as [1-3] from de Groat’s group for the top down control, which is not discussed here. This chapter focuses primarily on outlining the challenges in the development of computational model of the neural circuit that controls the LUT. Section 2 describes the anatomy of the LUT with primary focus on the neural anatomy. We describe the overall efferent and afferent neural pathways of LUT and briefly discuss the neurotransmitters involved and known details related to species/sex differences and developmental changes. Section 3 provides a brief summary of efforts to model the various neural components of the LUT for the purpose of understanding how they might participate in control. We list challenges in modeling the control of LUT at cellular and network levels and finally provide a brief description of an on-going effort to develop a biophysical model of the system.