Intercellular calcium waves in cultured enteric glia from neonatal guinea pig

Enteric glia are important participants in information processing in the enteric nervous system. However, intercellular signaling mechanisms in enteric glia remain largely unknown. We postulated that intercellular calcium waves exist in enteric glia. Primary cultures of enteric glia were isolated from neonatal guinea pig taenia coli. Intracellular calcium in individual cells was quantified with fura-2 AM microfluorimetry. Single-cell stimulation was performed with a micromanipulator-driven glass pipette. Data were expressed as mean ± SEM and analyzed by Student's t-test. Mechanical stimulation of a single enteric glial cell resulted in an increase in intracellular calcium, followed by concentric propagation to 36% ± 3% of neighboring cells. Intercellular calcium waves were blocked by depletion of intracellular calcium stores with thapsigargin (1 μM). Pretreatment of enteric glia with the phospholipase C inhibitor U73122 (1 μM) significantly decreased the percentage of cells responding to mechanical stimulation (6% ± 4%), but had no effect on waves induced by microinjection of the inositol trisphosphate (67% ± 13% vs. 60% ± 4% for control). Antagonism of inositol trisphosphate receptor attenuated intercellular calcium waves induced by both mechanical stimulation and microinjection of inositol trisphosphate. Uncoupling of gap junctions with octanol or heptanol significantly inhibited intercellular calcium wave propagation. Pretreatment of enteric glia with apyrase partially attenuated intercellular calcium waves. Our data demonstrate that enteric glial cells are capable of transmitting increases in intracellular calcium to surrounding cells, and that intercellular calcium waves involve a sequence of intracellular and extracellular steps in which phospholipase C, inositol trisphosphate, and ATP play roles.