Adenosine 5′-triphosphate-evoked calcium responses in terminal Schwann cells of lanceolate sensory endings isolated from rat vibrissae

Abstract

Extracellular adenosine 5′-triphosphate (ATP) has been known to mediate and modulate cutaneous sensations. We examined the effect of this substance on isolated terminal Schwann cells associating with lanceolate endings, the mechanoreceptors of rat vibrissae. The free intracellular calcium concentration ([Ca 2+] i) of the sensory device was monitored by digital image microscopy in combination with a calcium-sensitive fluorescent probe, Fura-2. Application of ATP in concentrations raging from 10 μM to 1 mM evoked an increase in [Ca 2+] i in Schwann cell processes covering the lancet-like axon terminals as well as in round perikarya of the cells protruding from the terminals. In both portions, the ATP-evoked [Ca 2+] i elevations were slowly oscillatory at 10 and 20 μM, and continuous at concentrations higher than 50 μM. Suramin 100 μM blocked the effect of ATP. Uridine 5′-triphosphate was equipotent with ATP, while α,β-methylene ATP was ineffective. These data indicate that the terminal Schwann cells express P2Y purinoceptors linked with the intracellular Ca 2+ signaling, and that this phenomenon is involved in the ATP-mediated sensory modulation.