Effects of ATP on intracellular calcium dynamics of the perineurium of peripheral nerve bundles

Adenosine-5'-triphosphate (ATP) released from damaged cells can affect func tions of adjacent cells. Injuries of peripheral tissue stimulate nerves, bu t effect of ATP on the nerve bundles is still speculative. Peripheral nerve s are surrounded by perineurium, therefore the response of perineurium may be a first event of nerve stimulation at tissue injuries. The aim of the pr esent study is to clarify whether the perineurium responds to ATP. To this end, we analyzed the dynamics of the intracellular calcium concentration ([ Ca2+](i)) of perineurial cells by confocal microscopy. ATP induced a [Ca2+] (i) increase of perineurial cells. Ca2+ channel blockers and removing of ex tracellular Ca2+, but not thapsigargin pretreatment, abolished ATP-induced [Ca2+](i) dynamics. This indicated that the [Ca2+](i) increase was due to a n influx of extracellular Ca2+. Adenosine-5'-diphosphate also elicited an i ncrease of [Ca2+](i), but PI receptor agonists had few effects on [Ca2+](i) dynamics. Suramin (an antagonist of P2X and P2Y receptors) totally inhibit ed ATP-induced [Ca2+](i) dynamics, but reactive blue 2 (a P2Y receptor anta gonist) did not. Uridine-5'-triphosphate (a P2Y receptor agonist) induced n o significant change in [Ca2+](i), but alpha,beta -methylene ATP (a P2X rec eptor agonist) caused a [Ca2+](i) increase. In conclusion, perineurial cell s respond to extracellular ATP mainly via P2X receptors.