In myenteric neurons two different receptor subtypes govern the intracellular Ca2+ stores: the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) and the ryanodine receptor (RyR). Their degree of functional overlap was determined by examining Ca2+ release in these cells through both superfusion techniques and intracellular microinjection. Microinjection of IP3 (50 μM) and cADP-ribose (cADPr, 50 μM), specific ligands for the IP3R and RyR, respectively, demonstrated mobilization of intracellular Ca2+ stores. Perfusion with cinnarizine (50 μM) or dantrolene (10 μM), antagonists of the IP3R and RyR, respectively, eliminated the Ca2+ response to microinjected IP3 and cADPr. Superfusion of the neurons with 100 μM ATP, an IP3-mediated Ca2+-mobilizing agonist, caused intracellular Ca2+ increments, which were antagonized by cinnarizine, and the RyR antagonists dantrolene, procaine (5 mM), and ryanodine (1 μM). 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 after repetitive ATP exposures. The internal Ca2+ stores of myenteric neurons are governed by two receptor subtypes, IP3R and RyR, which share partial functional overlap.
|Original language||English (US)|
|Journal||American Journal of Physiology - Gastrointestinal and Liver Physiology|
|Issue number||1 44-1|
|State||Published - Jan 1 2001|
- Adenosine 3′,5′-cyclic diphosphate-ribose
- Inositol 1,4,5-trisphosphate
- Myenteric plexus