Oscillatory calcium responses mediated by P2Y 2 purinergic receptors in terminal Schwann cells of longitudinal lanceolate endings isolated from rat vibrissae

The longitudinal lanceolate endings are mechanoreceptors that detect hair movement. We have previously shown that terminal Schwann cells, glial elements of the sensory devices, respond to an application of the sensory modulator adenosine 5′‐triphosphate (ATP) by an elevation in the intracellular Ca 2+ concentration ([Ca 2+ ] i ), suggesting a regulatory role for these cells in the cutaneous sensation. To define the spatiotemporal dynamics of the cell signaling and the pharmacological properties of the receptors responsible, arrays of the lanceolates were enzymatically isolated from the rat vibrissal follicle and subjected to [Ca 2+ ] i image recording by time‐lapse confocal microscopy during bath application of ATP analogues. The terminal Schwann cells formed extensive networks, connecting with one another by their lamellar processes associated with lanceolate axon endings. Stimulation of the cells with 100 μM ATP evoked [Ca 2+ ] i waves propagating along the cell processes. In each Schwann lamella, the initial wave evoked by a given trial of the stimulant arose from a specific locus within the cell process, whereas subsequent waves were sometimes observed to travel from its proximal portion. This implies a subcellular compartmentalization that may enable each Schwann lamella to modulate the activity of its accompanying lanceolate terminal through its own Ca 2+ signal as well as to regulate neighboring lanceolates through interlamellar signal propagation. Pharmacological experiments have shown that the Schwann cell responses are mediated by the P2Y 2 receptor, which has recently been reported to couple to multiple effector molecules in addition to stimulating the phosphoinositide signaling pathway involved in various glia–neuron interactions. J. Comp. Neurol. 475:416–425, 2004. © 2004 Wiley‐Liss, Inc.