The relationship between depletion of intracellular Ca2+ stores and activation of Ca2+ current by muscarinic receptors in neuroblastoma cells.

• DOI: 10.1085/jgp.106.5.975
• Publication Date: 2004-05-13T23:51:34Z
• Authors: C Mathes; S H Thompson
• Keywords: Thapsigargin; Fura-2; Second messenger system; EGTA

The relationship between the depletion of IP3-releasable intracellular Ca2+ stores and activation Ca(2+)-selective membrane current was determined during stimulation M1 muscarinic receptors in N1E-115 neuroblastoma cells. External is required for refilling voltage-independent, receptor-regulated represents a significant source refilling. time course store measured with fura-2 fluorescence imaging, it compared nystatin patch voltage clamp. At maximum density (0.18 + .03 pA/pF; n = 48), content pool reduced to 39 3% (n 10) its resting value. Calcium deplete rapidly, reaching minimum 15-30 s. delayed by 10-15 s after beginning release continues gradually increase nearly 60 s, long has peaked subsided. delay appearance consistent idea that production accumulation second messenger rate-limiting step activation. also adding thapsigargin block ATPase. After 15 min thapsigargin, are depleted > 90% maximal (0.19 0.05 6). Intracellular loading buffer EGTA/AM (10 microM; 30 min) depletes 25 50%, activates voltage-independent inward properties similar activated agonist or thapsigargin. (0.61 0.32 4) three times greater than response This could result from partial removal Ca(2+)-dependent inactivation.