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The Journal of Neuroscience, April 1, 1998, 18(7):2377-2386
Oxytocin Modulates Glutamatergic Synaptic Transmission between Cultured Neonatal Spinal Cord Dorsal Horn Neurons
Young-Hwan Jo, Marie-Elisabeth Stoeckel, Marie-José Freund-Mercier, and Rémy Schlichter Laboratoire de Neurophysiologie Cellulaire et Intégrée, Unité Mixte de Recherche 7519-Centre National de la Recherche Scientifique, Université Louis Pasteur, 67084 Strasbourg Cedex, France
The functional characteristics of binding sites for the neuropeptide oxytocin (OT) detected by radioautography in laminae I and II of the dorsal horn (DH) and on cultured neonatal DH neurons were studied on the latter using perforated patch-clamp recordings. The neurons were identified by their spike discharge properties and on the basis of the presence of met-enkephalin-like and glutamate decarboxylase-like immunoreactivities. OT (100 nM) never induced any membrane current at a holding potential of
60 mV but increased the frequency of spontaneously occurring AMPA receptor-mediated EPSCs or the mean amplitude of electrically evoked EPSCs in a subset (35%) of neurons. The frequency of miniature EPSCs (m-EPSCs) recorded in the presence of 0.5 µM tetrodotoxin was also increased by OT (100 nM) without any change in their mean amplitude, indicating an action at a site close to the presynaptic terminal. The decay kinetics of any type of EPSC were never modified by OT. The effect of OT was reproduced by [Thr4,Gly7]-OT (100 nM), a selective OT receptor agonist, and blocked by d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH29]-ornithine vasotocin (100 nM), a specific OT receptor antagonist. Reducing the extracellular Ca2+ concentration from 2.5 to 0.3 mM in the presence of Cd2+ (100 µM) reversibly blocked the effect of OT on m-EPSCs. The OT receptors described here may represent the substrate for modulatory actions of descending hypothalamo-spinal OT-containing pathways on the nociceptive system.
Key words: EPSCs; oxytocin; AMPA receptors; nociception; Met-enkephalin; GABA; dorsal horn neurons; spinal cord
Copyright © 1998 Society for Neuroscience 0270-6474/98/1872377-10$05.00/0
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