ATP modulation of synaptic transmission in the spinal substantia gelatinosa

Abstract

Actions of adenosine triphosphate (ATP) on neurons of the substantia gelatinosa (SG) were evaluated in spinal cord slices using tight-seal, whole-cell recordings. Bath-applied ATP activated a fast inward current and potentiated both glutamate-induced and synaptically evoked currents by acting through a purinergic receptor with the pharmacology of the P2 type. ATP also induced a delayed slow outward current and depressed synaptic currents that appeared to result from hydrolysis of ATP to adenosine. The inhibitory actions had features suggesting mediation by a P1-like purinergic receptor. Suramin, a putative P2 antagonist, inhibited ATP-induced fast inward currents but did not suppress synaptic currents evoked by dorsal root stimulation. It was concluded that in the SG, ATP released in synaptic regions acts as a synaptic modulator by augmenting excitatory amino acid actions and possibly by also producing a secondary adenosine inhibition.