Dj. Turner et al., Functional overlap of IP3- and cADP-ribose-sensitive calcium stores in guinea pig myenteric neurons, AM J P-GAST, 281(1), 2001, pp. G208-G215
Citations number
35
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
In myenteric neurons two different receptor subtypes govern the intracellul
ar Ca2+ stores: the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) and
the ryanodine receptor (RyR). Their degree of functional overlap was determ
ined by examining Ca2+ release in these cells through both superfusion tech
niques and intracellular microinjection. Microinjection of IP3 (50 muM) and
cADP-ribose (cADPr, 50 muM), specific ligands for the IP3R and RyR, respec
tively, demonstrated mobilization of intracellular Ca2+ stores. Perfusion w
ith cinnarizine (50 muM) or dantrolene (10 muM), antagonists of the IP3R an
d RyR, respectively, eliminated the Ca2+ response to microinjected IP3 and
cADPr. Superfusion of the neurons with 100 muM ATP, an IP3-mediated Ca2+-mo
bilizing agonist, caused intracellular Ca2+ increments, which were antagoni
zed by cinnarizine, and the RyR antagonists dantrolene, procaine (5 mM), an
d ryanodine (1 muM). Caffeine (10 mM) was applied repetitively in Ca2+-free
conditions to deplete RyR-sensitive stores; subsequent perfusion with ATP
demonstrated a Ca2+ response. Conversely, caffeine caused a Ca2+ response a
fter repetitive ATP exposures. The internal Ca2+ stores of myenteric neuron
s are governed by two receptor subtypes, IP3R and RyR, which share partial
functional overlap.