Quantal ATP release from acutely isolated cortex cells on single bouton level
The ATP postsynaptic currents were measured during local extracellular electrical stimulation of one single bouton of acutely isolated cortex cells. The successful mediator fusion events were visually controlled by stimulus activating staining by SynaptoGreen. The ATP was released from distinct vesicle population as evidence by existence of two separate populations of synaptic currents. As membrane potential was set above the reversal potential for Cl-, we observed fast inward currents mediated by P2X receptors and slow outward currents mediated by GABA. Furthermore, these two populations of synaptic currents we separated by pharmacological tools. When slow outward postsynaptic currents we inhibited by picrotoxin, the residual fast inward currents were blocked by 30 μM PPADS. The quantal parameters of postsynaptic currents in the cortical cells were obtained and verifi ed using maximum likelihood and autocorrelation techniques. The amplitude histograms for both mediators have a binominal distribution character with quantal size near 6.5 pA for ATP and 10 pA for GABA. In a conclusion, our results demonstrate that release of ATP in cortical inhibitory terminals occurs from separate pool of synaptic vesicles. Upon excitation of postsynaptic site release of ATP and GABA can be synchronized when both transmitters are released in multivesicular package.