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Stereoselective modulatory actions of oleamide on GABA A receptors and voltage‐gated Na + channels in vitro : a putative endogenous ligand for depressant drug sites in CNS
Author(s) -
Verdon Bernard,
Zheng Jian,
Nicholson Russell A,
Ganelli C Robin,
Lees George
Publication year - 2000
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703051
Subject(s) - veratridine , excitatory postsynaptic potential , chemistry , gabaa receptor , electrophysiology , inhibitory postsynaptic potential , pharmacology , neurotransmission , sodium channel , biophysics , neuroscience , receptor , biochemistry , biology , sodium , organic chemistry
cis ‐9,10‐octadecenoamide (‘oleamide’) accumulates in CSF on sleep deprivation. It induces sleep in animals (the trans form is inactive) but its cellular actions are poorly characterized. We have used electrophysiology in cultures from embryonic rat cortex and biochemical studies in mouse nerve preparations to address these issues. Twenty μ M cis ‐oleamide (but not trans ) reversibly enhanced GABA A currents and depressed the frequency of spontaneous excitatory and inhibitory synaptic activity in cultured networks.cis ‐oleamide stereoselectively blocked veratridine‐induced (but not K + ‐induced) depolarisation of mouse synaptoneurosomes (IC 50 , 13.9 μ M ). The cis isomer stereoselectively blocked veratridine‐induced (but not K + ‐induced) [ 3 H]‐GABA release from mouse synaptosomes (IC 50 , 4.6 μ M ). At 20 μ M cis ‐oleamide, but not trans , produced a marked inhibition of Na + channel‐dependent rises in intrasynaptosomal Ca 2+ . The physiological significance of these observations was examined by isolating Na + spikes in cultured pyramidal neurones. Sixty‐four μ M cis ‐oleamide did not significantly alter the amplitude, rate of rise or duration of unitary action potentials (1 Hz).cis ‐Oleamide stereoselectively suppressed sustained repetitive firing (SRF) in these cells with an EC 50 of 4.1 μ M suggesting a frequency‐ or state‐dependent block of voltage‐gated Na + channels. Oleamide is a stereoselective modulator of both postsynaptic GABA A receptors and presynaptic or somatic voltage‐gated Na + channels which are crucial for synaptic inhibition and conduction. The modulatory actions are strikingly similar to those displayed by sedative or anticonvulsant barbiturates and a variety of general anaesthetics. Oleamide may represent an endogenous modulator for drug receptors and an important regulator of arousal.British Journal of Pharmacology (2000) 129 , 283–290; doi: 10.1038/sj.bjp.0703051