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