ATP-gated P2X receptors on excitatory nerve terminals onto interneurons initiate a form of asynchronous glutamate release.
Previous work has shown that ATP-gated P2X2 receptors are expressed in excitatory nerve terminals onto stratum radiatum interneurons in the mouse hippocampal CA1 region. At these synapses receptor activation results in calcium-dependent facilitation of miniature and spontaneous EPSC frequency. In this study I determined if activation of presynaptic P2X receptors produces these effects by utilizing the vesicles underlying action potential dependent release. Brief trains of electrical stimuli caused short-term synaptic depression of excitatory synapses onto interneurons, in a manner consistent with depletion of the readily releasable pool of vesicles. P2X receptor activation increased the frequency of spontaneous EPSCs, but unexpectedly evoked little effect on synaptic depression. This suggests that P2X receptor activation does not markedly draw on the vesicles underlying action potential dependent glutamate release. However asynchronous EPSCs were increased following synaptic depression and a component of these appeared to be initiated by endogenously released ATP acting on presynaptic P2X receptors. Unexpectedly, the data suggest P2X receptor activation initiates a form of asynchronous glutamate release, rather than detectably affecting the vesicles underlying action potential evoked release.
Khakh
Baljit S
BS
Department of Physiology, David Geffen School of Medicine, University of California Los Angeles, CA 90095-1751, USA. bkhakh@mednet.ucla.edu
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D055592:Biophysical Phenomena; D004558:Electric Stimulation; D006624:Hippocampus / Q000166:cytology; D066298:In Vitro Techniques; D053444:Inhibitory Postsynaptic Potentials / Q000502:physiology / Q000528:radiation effects; D007395:Interneurons / Q000187:drug effects / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000502:physiology*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X
D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; C022571:adenosine 5'-O-(3-thiotriphosphate); D000255:Adenosine Triphosphate