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Adrenergic and cholinergic inhibition of Ca2+ channels mediated by different GTP-binding proteins in rat sympathetic neurones (1991)

Song, S. -Y. ; Saito, K. ; Noguchi, K. ; [et al.]

Springer

Pflügers Archiv 418 (1991), S. 592-600

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ISSN: 1432-2013

Keywords: Ca2+ channels ; G protein ; Sympathetic ganglion ; Acetylcholine ; Noradrenaline ; Muscarinic receptors ; α-adrenergic receptors

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Effects of acetylcholine (ACh) and noradrenaline (NA) on voltage-gated ion channels of sympathetic neurones acutely dissociated from rat superior cervical ganglion (SCG) were examined using the whole-cell voltage-clamp technique. Depolarizing voltage steps elicited two types of low- and high-voltage-activated (LVA and HVA) Ca2+ currents. Pressure applications of ACh and NA produced concentration-dependent inhibition of the HVA Ca2+ current without affecting the LVA Ca2+ current. The inhibitory action of ACh on the Ca2+ current was blocked by a muscarinic antagonist, atropine. The action of NA was suppressed by an α 2-adrenergic antagonist, yohimbine, but not by an α 1-adrenergic antagonist, prazosin. Delayed rectifying outward K+ currents and inward rectifying K+ current were not affected by either ACh or NA. Tetrodotoxin-sensitive and -insensitive Na+ currents also remained unaffected under actions of ACh and NA. When recorded with electrode containing guanosine-5′-O-(3-thiotriphosphate) (GTP-γ-S), the inhibitory actions of ACh and NA on Ca2+ currents became irreversible. After treatment of SCG neurones with pertussis toxin, the inhibitory action of ACh on the Ca2+ current was almost completely abolished, whereas the action of NA was only partially reduced. The results suggest that ACh and NA differentially inhibit the HVA Ca2+ current via different G proteins coupling muscarinic and α 2-adrenergic receptors to Ca2+ channels in rat SCG neurones.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00370576

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Scanning electron microscope study of the splenic red pulp in relation to the sequestration of immature and abnormal red cellsThis investigation was supported by Grant MA-4799 from the Medical Research Council of Canada. (1974)

Song, S. H. ; Groom, A. C.

New York, NY : Wiley-Blackwell

Journal of Morphology 144 (1974), S. 439-451

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ISSN: 0362-2525

Keywords: Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Medicine

Notes: Spleens from normal, healthy cats, dogs and rabbits were perfused with Ringer solution until only a few red cells remained. After fixation of the intact organ, small pieces of tissue were dried by a camphene method and examined under the scanning electron microscope. In all three species the red cells remaining in the spleen were either reticulocytes, spiculated cells, or cells of tear-drop shape and they were found adhering to macrophages and reticulum cells throughout the red pulp. Elongated masses were found on the sinusal surface of fenestrated endothelium (only in dog and rabbit); some of these appeared to be cells of tear-drop shape emerging from the cords into the sinus. This may perhaps denote a pitting process, as suggested by others, but it cannot be a unique function of fenestrated endothelium for red cells of similar shape were found elsewhere in the pulp. In all three species the network of reticulum fibres presents a very large contact surface area for blood cells and it seems likely that increased cell stickiness, rather than decreased deformability, leads to the trapping of immature red cells in the spleen.