A dual system of intercellular calcium signaling in glial nets associated with lanceolate sensory endings in rat...

The lanceolate sensory endings that form palisades around the hair follicle associate with networks of branched Schwann cells. To define the properties of these glial networks as possible conduits of Ca2+ signals, lanceolate endings isolated from rat vibrissae were observed by confocal microscopy while the signaling was locally activated by mechanical stimulation. Intercellular coupling by gap junctions was also assessed by a technique employing fluorescence recovery after photobleaching (FRAP) and by transmission electron microscopy (TEM). Results showed that the glial Ca2+ signals can spread among the arrays of lanceolates in two forms: rapid signals that originate in individual Schwann processes covering the lanceolate axon terminals around the locus of mechanical stimulation, and delayed ones that travel from the stimulation locus through cytoplasmic arborization of the primarily activated cell to the adjacent cell processes. The former signaling was suppressed by the antipurinergic agents suramin and apyrase, whereas the latter was sensitive to the gap junction blocker carbenoxolon. FRAP experiments and TEM observations corroborated the presence of gap junction communications between the Schwann processes of different cell origins. These findings show that, in the Schwann networks, purinergically induced Ca2+ signals and those dependent on gap junctions are propagated in their own spatiotemporal patterns to constitute two distinct forms of communication among the mechanoreceptor palisades.