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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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Effect of intramolecular and intermolecular exchange processes on the 1H NMR spectra of 2-chloro-1,3,2-dioxarsolanes (1987)

Song, S. K. ; Watkins, C. L. ; Krannich, L. K.

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 25 (1987), S. 484-488

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ISSN: 0749-1581

Keywords: 1H NMR ; 13C NMR ; 2-Chloro-1,3,2-dioxarsolanes ; Intra- and inter-molecular exchange ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The 1H and 13C NMR spectra of solutions of 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxarsolane (1) and 2-chloro-1,3,2-dioxarsolane (2) are reported as a function of temperature, concentration and solvent. These data indicate rapid intramolecular conformational averaging for (1) and (2) under all the conditions investigated. Additionally, intermolecular conformational averaging processes are shown to be present. The kinetic parameters for intermolecular exchange were obtained from line shape analysis of the 1H NMR data. These results indicate the intermolecular exchange to be bimolecular in nature, involving a four-centered transition state. The O—CH2—CH2-O torsional angle of (2) has been calculated from the analysis of its AA′BB′ 1H NMR spectral patterns, obtained at low concentrations in the absence of intermolecular exchange.

Additional Material: 2 Ill.