University of Central Florida Undergraduate Research Journal - Anatomy and Function of Autonomic Innervation of the Liver
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Anatomy and Function of Autonomic Innervation
of the Liver

By: Kennan Negrete | Mentor: Dr. Zixi Cheng

Introduction

The liver is a key regulatory organ of both glucose and lipid metabolism, and various studies have shown that autonomic innervation plays a role in the regulation of hepatic function (Akiyoshi, Gonda, & Terada, 1998; Berthoud, 2004; Kalsbeek et al., 2010; McCuskey, 2004; Perez-Tilve et al., 2010; Tunderaher, Farr, & Adeli, 2017; Verma, Antony, Ogunnaike, Hoek, & Vadigepalli, 2018; Yi, la Fleur, Fliers, & Kalsbeek, 2010). This liver-brain axis is under-studied, with many unknowns regarding its structure, function, and scope (Akiyoshi et al., 1998; Berthoud, 2004; Kalsbeek et al., 2010; McCuskey, 2004; Perez-Tilve et al., 2010; Taher et al., 2017; Verma et al., 2018; Yi et al., 2010). Additionally, in liver transplant cases, autonomic innervation of hepatic tissue is significantly reduced, yet the liver continues to function at a level that deviates only moderately from normal (Tiniakos, Lee, & Burt, 1996; Yi et al., 2010). The study of the liver-brain axis is further complicated by large anatomical differences in nerve distribution between rodents and higher mammals, particularly in the parenchyma (Akiyoshi et al., 1998; McCuskey, 2004; Verma et al., 2018). Despite these obstacles, the study of the neural map of the liver provides a link between the organ’s many functions and the influence of the autonomic nervous system. This review summarizes knowledge concerning the form and function of hepatic sensory and motor innervation acquired over the last five decades. Among the topics covered are the anatomical neural map of the rodent liver, which notably lacks intrahepatic ganglia (Berthoud, 2004; Berthoud and Neuhuber, 2000; Taher et al., 2017), as well as the influence of the sympathetic and parasympathetic nervous system upon various metabolic and regulatory pathways. While substantial evidence implicates the hypothalamus and autonomic nervous system in various modifications of liver activity, the precise mechanisms and interplay of the nervous, endocrine, and hepatic systems have yet to be fully elucidated.  Understanding of the liver-brain axis is still far from complete, but technological advances may allow many of the topics covered here to be revisited and explored in far greater depth than was previously possible. These advances, in turn, could potentially lead to the discovery of novel, neural-based treatments for chronic liver disease.

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