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
Permalink
