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Effects of steroids on NMDA receptors and excitatory synaptic transmission in neonatal motoneurons in rat spinal cord slices
Author(s) -
Abdrachmanova Galya,
Chodounská Hana,
Vyklický Ladislav
Publication year - 2001
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.0953-816x.2001.01663.x
Subject(s) - nmda receptor , excitatory postsynaptic potential , chemistry , conductance , neurotransmission , biophysics , neuroscience , postsynaptic current , receptor , postsynaptic potential , spinal cord , biology , biochemistry , physics , condensed matter physics
The effect of steroids on NMDA receptors and excitatory postsynaptic transmission was studied in fluorescence‐labelled motoneurons in thin spinal cord slices. In outside‐out patches, NMDA‐induced responses were potentiated by 79% in the presence of 20‐oxopregn‐5‐en‐3β‐yl sulfate (PS), while in the presence of 20‐oxo‐5α‐pregnan‐3α‐yl sulfate (3α5αS) and 20‐oxo‐5β‐pregnan‐3α‐yl sulfate (3α5βS) they were diminished by 57% and 66%, respectively. PS and 3α5βS had no effect on the amplitude of single NMDA receptor channel openings, however, both compounds altered relative distribution of the openings to individual conductance levels. In control cases, the most frequent openings of the NMDA receptor channels were at the 70 pS conductance level, while in the presence of PS or 3α5βS, the most frequent openings were at the 55 pS conductance level. Analysis of the mean current transferred by NMDA receptor channel openings at individual conductance levels indicated that in the presence of PS, the mean current induced by 55 pS conductance openings was significantly increased. In the presence of 3α5βS, the mean currents induced by 55 pS and 70 pS conductance openings were significantly decreased. The amplitude of NMDA receptor‐mediated EPSCs was potentiated by 54% in the presence of PS and the deactivation kinetics slowed. Neither the amplitude nor the kinetics of NMDA receptor‐mediated EPSCs was significantly changed in the presence of 3α5βS. The results of our experiments indicate that neurosteroids affect NMDA receptors in motoneurons. The effect appears to be influenced by the receptor subunit composition.