Abstract
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.
Original language | English (US) |
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Pages (from-to) | 2377-2386 |
Number of pages | 10 |
Journal | Journal of Neuroscience |
Volume | 18 |
Issue number | 7 |
DOIs | |
State | Published - Apr 1 1998 |
Externally published | Yes |
Keywords
- AMPA receptors
- Dorsal horn neurons
- EPSCs
- GABA
- Met-enkephalin
- Nociception
- Oxytocin
- Spinal cord
ASJC Scopus subject areas
- General Neuroscience