The role of glycine as an inhibitory neurotransmitter is well established, and glycinergic neurons appear to play an important role in the mammalian retinae[Ikeda & Sheardown, 1983 ; Bolz et al., 1985]. Though it has been reported that certain conventional and displaced amacrine cells and a few of bipolar cells are consistently labeled with anti-glycine antiserum in the mammalian retinae so far[W ssle et al., 1986 ; Pourcho & Goebel, 1987 ; Davanger et al., 1991 ; Yoo & Chung, 1992], little has been studied on the synaptic circuitry of glycinergic neurons to clarify mechanism of its action in the visual processing of the mammalian retinae. This study was conducted to localize glycinergic neurons and to define their synaptic circuitry in the rat retina by immunocytochemical method using anti -glycine antiserum. The results were as follows : 1. Glycinergic neurons of the rat retina were conventional and displaced amacrine cells, interstitial cells and bipolar cells. 2. Glycinergic amacrine cells could be subdivided into two types, that is, A II amacrine cells and other amacrine cells, according to their ultrastructures. Glycinergic A II amacrine and other amacrine cell processes comprised postsynaptic dyad at the ribbon synapse of rod bipolar axon terminals in the sublamina b of the inner plexiform layer of the retina. Glycinprgic A II amacrine cell processes made gap junctions with axon terminals of unlabeled invaginating cone bipolar cells in the sublamina b, and made chemical synapses onto axon terminals of unlabeled flat cone bipolar cells and onto dendrites of ganglion cells in the sublamina a of the inner plexiform layer. In the sublamina b of the inner plexiform layer, g1ycinergic amacrine cell processes were postsynaptic to axon terminals of unlabeled invaginating cone bipolar cells, and made chemical output synapses onto axon terminals of unlabeled invaginating cone bipolar and rod bipolar cells and onto the dendrites of ganglion cells. Such cases that pre- and post-synaptic processes of glycinergic amacrine cell processes were non- glycinergic amacrine cell processes were frequently observed throughout the inner plexiform layer. In some cases, glycinergic amacrine cell processes receiving synaptic inputs from other glycinergic amacrine cell process made synaptic outputs onto the non-glycinergic or glycinergic amacrine cell processes. 3. Glycinergic bipolar cells could be subdivided into invaginating and flat cone bipolar cells. Postsynaptic dyads of cone bipolar cells at the ribbon synapses were non-glycinergic amacrine and amacrine cell processes, glycinergic amacrine and amacrine cell processes, glycinergic amacrine and non-glycinergic amacrine cell processes, and dendrite and dendrite of ganglion cells. These results demonstrate that [1] glycinergic A II amacrine cell receiving synaptic input from rod bipolar cells inhibit flat cone bipolar cells and OFF ganglion cells via chemical synapse, and excite ON cone bipolar cells via electrical synapse ; thereby visual information in the darkness can be transmitted to ON ganglion cells via ON cone bipolar cells, and [2] glycine released from glycinergic neurons inhibits directly ON and OFF ganglion cells or indirectly ON and OFF ganglion cells via non-glycinergic amacrine or bipolar cells.
Amacrine Cells ; Animals ; Darkness ; Dendrites ; Electrical Synapses ; Ganglion Cysts ; Gap Junctions ; Glycine ; Neurons* ; Neurotransmitter Agents ; Presynaptic Terminals ; Rats* ; Retina* ; Synapses

BACKGROUND: In mammals, the master circadian pacemaker is localized in an area of the ventral hypothalamus known as the suprachiasmatic nucleus (SCN). Previous studies have shown that pacemaker neurons in the SCN are highly coupled to one another, and this coupling is crucial for intrinsic self-sustainability of the SCN central clock, which is distinguished from peripheral oscillators. One plausible mechanism underlying the intercellular communication may involve direct electrical connections mediated by gap junctions. METHODS: We examined the effect of mefloquine, a neuronal gap junction blocker, on circadian Period 2 (Per2) gene oscillation in SCN slice cultures prepared from Per2::luciferase (PER2::LUC) knock-in mice using a real-time bioluminescence measurement system. RESULTS: Administration of mefloquine causes instability in the pulse period and a slight reduction of amplitude in cyclic PER2::LUC expression. Blockade of gap junctions uncouples PER2::LUC-expressing cells, in terms of phase transition, which weakens synchrony among individual cellular rhythms. CONCLUSION: These findings suggest that neuronal gap junctions play an important role in synchronizing the central pacemaker neurons and contribute to the distinct self-sustainability of the SCN master clock.
Animals ; Circadian Rhythm ; Electrical Synapses ; Gap Junctions* ; Hypothalamus ; Luminescent Measurements ; Mammals ; Mefloquine* ; Mice* ; Neurons ; Phase Transition ; Suprachiasmatic Nucleus*

Oculodentodigital dysplasia (ODDD) is a rare autosomal dominant inherited disease caused by mutations of the human gap junction alpha 1 gene, which encodes the protein Connexin-43. Patients with ODDD may present with neurological deficits with a typical pleiotropic combination of characteristic craniofacial, ophthalmological, phalangeal, and dental anomalies. In this report, we describe the first genetically confirmed Korean ODDD patient, who presented with spastic paraparesis. We will also review the neurological aspects of ODDD as reported in the literature.
Gap Junctions ; Humans ; Muscle Spasticity* ; Paraparesis, Spastic*

The aim of this study was to evaluate the histopathologic changes of the pigmented rabbit ratina after endocryopexy. We investigated the differences or similarity among endocryopexy, transscleral cryopexy and laser phocoagulation. Their ultrastructural changes were observed with light and electron microscope. The results were as follows; 1. The first day after endocryopexy, we observed rupture of the internal limiting membrane, breakdown the inner and outer retina, separation of intercellular gap junction of pigment epithelial cells, and accumulation of exudation within subretinal space. 2. In the 8th days, there are mull iplication of retinal pigment epithelial cell layer and development of basal infolding. 3. The present study suggested that effects of endocryopexy on the retina to cause chorioretinal adhesion was similar to transscleral cryopexy or laser photocoagulation However it should be operated on the premise that in requires technical skill for the purpose of clinical application.
Epithelial Cells ; Gap Junctions ; Light Coagulation ; Membranes ; Retina* ; Retinaldehyde ; Rupture

Horizontal cells (HCs) of the mammalian retina are interneurons that provide negative feedback to photoreceptors in the outer plexiform layer (OPL) where the first synapse occurs and contribute to the center surround antagonism that underlies the receptive field properties of many retinal neurons. These functions of HCs are thought to be attributed to their coupled network via gap junctions. Two kinds of connexin (Cx) proteins, Cx50 and 57 are known to form gap junctions of HCs. However, little is known about precise localization of gap junctions within HCs. Thus, this study was designed to determine the localization of HC gap junctions at subcellular level. In vertical ultrathin sections of the rabbit retina, gap junctions composed of Cx50 and 57 were identified in the OPL by the electron-dense reaction products. Each Cx50 and 57 gap junction on putative HC processes showed its own distinct features. Cx50 gap junction was bigger in size and localized more proximally than Cx57. In addition, Cx57 gap junctions had distinct shape. That is, about a half of them appeared to be invaginated or endocytosed in shape. The differences in shape, size and subcellular localization between Cx50 and 57 gap junctions may provide the insights into the function of different types of horizontal cell.
Gap Junctions ; Interneurons ; Proteins ; Retina ; Retinal Neurons ; Synapses

Connexins (Cx) are membrane proteins and monomers for forming gap junction (GJ) channels. Cx46 and Cx50 are also known to function as conductive hemichannels. As part of an ongoing effort to find GJ-specific blocker(s), endocrine disruptors were used to examine their effect on Cx46 hemichannels expressed in Xenopus oocytes. Voltage-dependent gating of Cx46 hemichannels was characterized by slowly activating outward currents and relatively fast inward tail currents. Bisphenol A (BPA, 10 nM) reduced outward currents of Cx46 hemichannels up to ~18% of control, and its effect was reversible (n=5). 4-tert-Octylphenol (OP, 1 microM) reversibly reduced outward hemichannel currents up to ~28% (n=4). However, overall shapes of Cx46 hemichannel current traces (outward and inward currents) were not changed by these drugs. These results suggest that BPA and OP are likely to occupy the pore of Cx46 hemichannels and thus obstruct the ionic fluxes. This finding provides that BPA and OP are potential candidates for GJ channel blockers.
Connexins ; Endocrine Disruptors ; Gap Junctions ; Membrane Proteins ; Oocytes ; Xenopus

The contractility of corporal smooth muscle plays a critical role in human penile erectile process. Understanding the initiation, maintenance and modulation of corporal smooth muscle tone is a prequisite to improve understanding, diagnosis and treatment of erectile dysfunction. Despite this fact, indentification of both the precise mechanistic basis by which various agents exert their effects on individual corporal smooth muscle cells, moreover, the process by which these signals are spread among the diverse array of parenchymal cells in the paired corporal, remain somewhat of a physiological enigma. Therefore, this article aims at: 1. to review current knowledge of the regulation of corporal smooth muscle tone at the cellular and molecular level; 2. to review various methods used in the study of gap junction channel.
Animals ; Connexins ; physiology ; Gap Junctions ; physiology ; Humans ; Intercellular Junctions ; physiology ; Male ; Muscle, Smooth ; physiology ; Penis ; cytology

Arrhythmias, Cardiac ; etiology ; therapy ; Gap Junctions ; Stem Cell Transplantation ; adverse effects

OBJECTIVETo investigate the possible relationship between the analgesic effect of acupuncture and connexin 43.

METHODSConnexin 43 gene knock-out mice were divided into 4 groups: a wide type (WT) control group, a WT acupuncture group, a heterozygous (HT) control group and HT acupuncture group. Hot-plate test and writhing response induced by acetic acid were used for investigating the analgesic effect of acupuncture.

RESULTSThere was no significant difference in the basic pain threshold value between HT and WT mice (P > 0.05). Acupuncture could significantly increase the pain threshold value, prolong the latency period of writhing body and decrease the number of writhing body as compared with pre-acupuncture in WT and HT mice (P < 0.01 or P < 0.05). The pain threshold, latency period of writhing and number of writhing body in HT mice were less than WT mice post-acupuncture (P < 0.05).

CONCLUSIONConnexin 43 gene knock-out might partially inhibit the analgesic effect of acupuncture, suggesting that connexin 43 is possibly related with meridians and the effect of acupuncture.

Acupuncture Analgesia ; Animals ; Connexin 43 ; genetics ; physiology ; Female ; Gap Junctions ; physiology ; Male ; Mice ; Pain Threshold

Little is known about how gap junctions are involved in the respiratory-related or other types of physiological neuronal activity since physiologically active gap junction currents (GJCs) have never been characterized from single respiratory-related neurons or from single neurons of any other types. In the present study we hypothesized that GJCs could be selectively revealed from single neurons by elimination of transmembrane electrochemical gradients in voltage patch-clamp recording, and this hypothesis was tested in single inspiratory tracheal preganglionic vagal motor neurons (I-TPVMs). The results showed that GJCs were selectively revealed in all I-TPVMs when the transmembrane electrochemical gradients were eliminated in voltage patch-clamp recording, and were rhythmically activated by central inspiratory activity. Therefore, this method may be used as a fast way to detect GJCs within spontaneously active neuronal networks.
Gap Junctions ; physiology ; Motor Neurons ; physiology ; Patch-Clamp Techniques ; Trachea ; cytology