Gap junctional coupling and patterns of connexin expression among neonatal rat lumbar spinal motor neurons

• Type of Material: Article
• Authors: Qiang Chang, University of Pennsylvania; Michael Gonzalez, University of Pennsylvania; Martin Pinter, Emory University; Rita J. Balice-Gordon, University of Pennsylvania
• Language: English
• Date: 1999-12-15
• Publisher: Society for Neuroscience
• Publication Version: Final Published Version
• Copyright Statement: Copyright © 1999 Society for Neuroscience
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1523/JNEUROSCI.19-24-10813.1999
• Title of Journal or Parent Work: Journal of Neuroscience Nursing
• ISSN: 0888-0395
• Volume: 19
• Issue: 24
• Start Page: 10813
• End Page: 10828
• Grant/Funding Information: This work was supported by grants from National Institutes of Health (NS34373), the Spinal Cord Research Foundation (1472), and the McKnight Foundation to R.B.-G.
• Keywords: XENOPUS OOCYTES; Neurosciences; NEWBORN RATS; Science & Technology; CIRCUIT FORMATION; gap junction; SKELETAL-MUSCLE FIBERS; motor neuron; Life Sciences & Biomedicine; CELLS; NEUROMUSCULAR-JUNCTION; POLYNEURONAL INNERVATION; neuromuscular junction; spinal cord; NERVOUS-SYSTEM; activity; DEVELOPING NEOCORTEX; connexin; Neurosciences & Neurology; MOLECULAR-CLONING
• Research Categories: Biology, Neuroscience; Biology, Animal Physiology

Abstract

Interneuronal gap junctional coupling is a hallmark of neural development whose functional significance is poorly understood. We have characterized the extent of electrical coupling and dye coupling and patterns of gap junction protein expression in lumbar spinal motor neurons of neonatal rats. Intracellular recordings showed that neonatal motor neurons are transiently electrically coupled and that electrical coupling is reversibly abolished by halothane, a gap junction blocker. Iontophoretic injection of Neurobiotin, a low molecular weight compound that passes across most gap junctions, into single motor neurons resulted in clusters of many labeled motor neurons at postnatal day 0 (P0)-P2, and single labeled motor neurons after P7. The compact distribution of dye-labeled motor neurons suggested that, after birth, gap junctional coupling is spatially restricted. RT-PCR, in situ hybridization, and immunostaining showed that motor neurons express five connexins, Cx36, Cx37, Cx40, Cx43, and Cx45, a repertoire distinct from that expressed by other neurons or gila. Although all five connexins are widely expressed among motor neurons in embryonic and neonatal life, Cx36, Cx37, and Cx43 continue to be expressed in many adult motor neurons, and expression of Cx45, and in particular Cx40, decreases after birth. The disappearance of electrical and dye coupling despite the persistent expression of several gap junction proteins suggests that gap junctional communication among motor neurons may be modulated by mechanisms that affect gap junction assembly, permeability, or open state.