Gap junctions coordinate the propagation of glycogenolysis induced by norepinephrine in the pineal gland

Abstract

Chemical and electrical synapses are the two major communication systems that permit cell‐to‐cell communication within the nervous system. Although most studies are focused on chemical synapses (glutamate, γ‐aminobutyric acid, and other neurotransmitters), clearly both types of synapses interact and cooperate to allow the coordination of several cell functions within the nervous system. The pineal gland has limited independent axonal innervation and not every cell has access to nerve terminals. Thus, additional communication systems, such as gap junctions, have been postulated to coordinate metabolism and signaling. Using acutely isolated glands and dissociated cells, we found that gap junctions spread glycogenolytic signals from cells containing adrenoreceptors to the entire gland lacking these receptors. Our data using glycogen and lactate quantification, electrical stimulation, and high‐performance liquid chromatography with electrochemical detection, demonstrate that gap junctional communication between cells of the rat pineal gland allows cell‐to‐cell propagation of norepinephrine‐induced signal that promotes glycogenolysis throughout the entire gland. Thus, the interplay of both synapses is essential for coordinating glycogen metabolism and lactate production in the pineal gland.

Connexins and Glucose Metabolism in Cancer

“…However, in line with the dynamic and context-dependent nature of connexins, other studies in this area have shown no effect, or an upregulation in response to high glucose concentrations [ 204 , 205 , 206 , 207 , 208 ]. Conversely, other reports have shown the ability of connexins to directly influence aspects of glucose metabolism [ 155 , 209 , 210 , 211 , 212 , 213 ]. It is therefore clear that connexins are dynamically regulated by availability of glucose and simultaneously contribute to regulation of its metabolism.…”

<p>ZG02 Improved Hepatic Glucose Metabolism and Insulin Sensitivity via Activation of AMPK/Sirt1 Signaling Pathways in a High-fat Diet/Streptozotocin-induced Type 2 Diabetes Model</p>

“…The liver is a particularly important metabolic organ for controlling blood glucose and ~90% of endogenous glucose is produced by the hepatic system. 15 It can maintain blood glucose balance by regulating various pathways such as gluconeogenesis, 16,17 glycogenolysis, 18,19 glycogen synthesis and glycolysis. 20 Numerous studies show that gluconeogenesis contributes approximately half of the total hepatic glucose production (HGP) in humans following an overnight fast and inhibition of hepatic gluconeogenesis can significantly improve blood glucose in individuals with T2DM.…”