A series of structurally novel heterotricyclic alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptor-selective antagonists.
OBJECTIVE
A new class of heterotricyclic glutamate analogues recently was generated by incorporating structural elements of two excitotoxic marine compounds, kainic acid and neodysiherbaine A. Rather than acting as convulsants, several of these 'IKM' compounds markedly depressed CNS activity in mice. Here, we characterize the pharmacological profile of the series with a focus on the most potent of these molecules, IKM-159.


METHODS
The pharmacological activity and specificity of IKM compounds were characterized using whole-cell patch clamp recording from neurons and heterologous receptor expression systems, in combination with radioligand binding techniques.


RESULTS
The majority of the IKM compounds tested reduced excitatory synaptic transmission in neuronal cultures, and IKM-159 inhibited synaptic currents from CA1 pyramidal neurons in hippocampal slices. IKM-159 inhibited glutamate-evoked whole-cell currents from recombinant GluA2- and GluA4-containing alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptors most potently, whereas kainate and NMDA receptor currents were not reduced by IKM-159. Antagonism of steady-state currents was agonist concentration dependent, suggesting that its mechanism of action was competitive, although it paradoxically did not displace [(3)H]-AMPA from receptor binding sites. IKM-159 reduced spontaneous action potential firing in both cultured hippocampal neurons in control conditions and during hyperactive states in an in vitro model of status epilepticus.


CONCLUSIONS
IKM-159 is an AMPA receptor-selective antagonist. IKM-159 and related nitrogen heterocycles represent structurally novel AMPA receptor antagonists with accessible synthetic pathways and potentially unique pharmacology, which could be of use in exploring the role of specific populations of receptors in neurophysiological and neuropathological processes.
Gill
M B
MB
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Feinberg School of Medicine, Chicago, IL, USA.
Frausto
S
S
Ikoma
M
M
Sasaki
M
M
Oikawa
M
M
Sakai
R
R
Swanson
G T
GT
D000818:Animals; D001572:Benzofurans / Q000494:pharmacology*; D001665:Binding Sites; D002460:Cell Line; D005260:Female; D018698:Glutamic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D011760:Pyrrolidinones / Q000494:pharmacology*; D011869:Radioligand Assay; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors*; D013226:Status Epilepticus / Q000188:drug therapy / Q000503:physiopathology; D009435:Synaptic Transmission / Q000187:drug effects
D001572:Benzofurans; D006571:Heterocyclic Compounds; C552887:IKM 159; D011760:Pyrrolidinones; D018091:Receptors, AMPA; D018698:Glutamic Acid