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Lookup NU author(s): Dr Clive Ballard, Emeritus Professor Elaine Perry
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A dual radioligand binding and electrophysiological study, focusing on a range of ligand-gated ion channels, was performed with a chemically-validated essential oil derived from Melissa officinalis (MO), which has shown clinical benefit in treating agitation. MO inhibited binding of [35S] t-butylbicyclophosphorothionate (TBPS) to the rat forebrain gamma-aminobutyric acid (GABA)A receptor channel (apparent IC50 0.040±0.001 mg mL-1), but had no effect on N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropianate (AMPA) or nicotinic acetylcholine receptors. Electrophysiological analyses with primary cultures of rat cortical neurons demonstrated that MO reversibly inhibited GABA-induced currents in a concentration-dependent manner (0.01-1 mg mL-1), whereas no inhibition of NMDA- or AMPA-induced currents was noted. Interestingly, MO elicited a significant dose-dependent reduction in both inhibitory and excitatory transmission, with a net depressant effect on neurotransmission (in contrast to the classical GABAA antagonist picrotoxinin which evoked profound epileptiform burst firing in these cells). The anti-agitation effects in patients and the depressant effects of MO in in-vitro we report in neural membranes are unlikely to reflect a sedative interaction with any of the ionotropic receptors examined here. © 2008 The Authors.
Author(s): Abuhamdah S, Huang L, Elliott MSJ, Howes M-JR, Ballard C, Holmes C, Burns A, Perry EK, Francis PT, Lees G, Chazot PL
Publication type: Article
Publication status: Published
Journal: Journal of Pharmacy and Pharmacology
Year: 2008
Volume: 60
Issue: 3
Pages: 377-384
Print publication date: 01/03/2008
ISSN (print): 0022-3573
ISSN (electronic): 0373-1022
Publisher: John Wiley & Sons Ltd.
URL: http://dx.doi.org/10.1211/jpp.60.3.0014
DOI: 10.1211/jpp.60.3.0014
PubMed id: 18284819
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