Abstract
A small library of anilino enaminones was analyzed for potential anticonvulsant agents. We examined the effects of three anilino enaminones on neuronal activity of output neurons, mitral cells (MC), in an olfactory bulb brain slice preparation using whole-cell patch-clamp recording. These compounds are known to be effective in attenuating pentylenetetrazol-induced convulsions. Among the three compounds tested, 5-methyl-3-(4-trifluoromethoxy-phenylamino)-cyclohex-2-enone (KRS-5Me-4-OCF3) showed potent inhibition of MC activity with an EC50 of 24.5 μM. It hyperpolarized the membrane potential of MCs accompanied by suppression of spontaneous firing. Neither ionotropic glutamate receptor blockers nor a GABAB receptor blocker prevented the KRS-5Me-4-OCF3-evoked inhibitory effects. In the presence of GABAA receptor antagonists, KRS-5Me-4-OCF3 completely failed to evoke inhibition of MC spiking activity, suggesting that KRS-5Me-4-OCF3-induced inhibition may be mediated by direct action on GABAA receptors or indirect action through the elevation of tissue GABA levels. Neither vigabatrin (a selective GABA-T inhibitor) nor 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid hydrochloride (NNC-711) (a selective inhibitor of GABA uptake by GABA transporter 1) eliminated the effect of KRS-5ME-4-OCF3 on neuronal excitability, indicating that the inhibitory effect of the enaminone resulted from direct activation of GABAA receptors. The concentration-response curves for GABA are left-shifted by KRS-5Me-4-OCF3, demonstrating that KRS-5Me-4-OCF3 enhanced GABA affinity and acted as a positive allosteric modulator of GABAA receptors. The effect of KRS-5Me-4-OCF3 was blocked by applying a benzodiazepine site antagonist, suggesting that KRS-5Me-4-OCF3 binds at the classic benzodiazepine site to exert its pharmacological action. The results suggest clinical use of enaminones as anticonvulsants in seizures and as a potential anxiolytic in mental disorders.
Footnotes
This work was supported in part by the National Institute of Health National Institute of General Medical Sciences [Grant S06-GM08016]; the National Institutes of Health National Institute of Neurological Disorders and Stroke [Grant U54-NS039407]; and the Howard University New Faculty Research Program, the Howard University Health Sciences Faculty Seed Grant Program, the Whitehall Foundation.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.110.173740.
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ABBREVIATIONS:
- NMDA
- N-methyl-d-aspartate
- ACSF
- artificial cerebrospinal fluid
- MOB
- main olfactory bulb
- MC
- mitral cell
- KRS-5Me-4-OCF3
- 5-methyl-3-(4-trifluoromethoxy-phenylamino)-cyclohex-2-enone
- KRS-5Me-4-F
- 3-(4-fluoro-phenylamino)-5-methyl-cyclohex-2-enone
- KRS-5Me-3-Cl
- 3-(3-chloro-phenylamino)-5-methyl-cyclohex-2-enone
- DMSO
- dimethyl sulfoxide
- d-AP5
- l-2-amino-5-phosphonopentanoic acid
- CNQX
- 6-cyano-7-nitroquinoxaline-2-3-dione
- gabazine (SR-95531)
- 2-(3-carboxypropyl)-3-amino-6-(4 methoxyphenyl)-pyridazinium bromide
- LY367385
- (S)-(+)-α-amino-4-carboxy-2-methylbenzeneacetic acid
- CGP55845
- (2S)-3[[(1S0–1-(3,4-dichlorophenyl)ethyl]amino-2-hydroxypropyl](phenylmethyl) phosphinic acid
- (R)-baclofen
- (R)-4-amino-3-(4-chlorophenyl) butanoic acid
- NNC 711
- 1,2,5,6-tetrahydro-1-[2-[[(diphenylmethylene)amino]oxy]ethyl]-3-pyridinecarboxylic acid hydrochloride
- vigabatrin
- (±)-γ-vinyl GABA
- flumazenil
- 8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5-a][1,4]benzodiazepine-3-carboxylic acid, ethyl ester
- (S)-SNAP 5114
- 1-[2-[tris(4-methoxyphenyl)methoxy]ethyl]-(S)-3piperidinecarboxylic acid
- ANOVA
- analysis of variance
- AMPA
- α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid
- GABABR
- GABAB receptor
- GAT
- GABA transporter
- GABA-T
- GABA transaminase.
- Received August 5, 2010.
- Accepted December 7, 2010.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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