Ferenc Antoni

Interactions between intracellular free Ca2+ and cyclic AMP in neuroendocrine cells.

Calcium ions and cyclic adenosine monophosphate (cAMP) are virtually ubiquitous intracellular signaling molecules in mammalian cells. This paper will focus on the cross-talk between Ca(2+) and cAMP mobilizing signaling pathways and summarize the underlying molecular mechanisms. Subsequently, workings of adenohypophyseal corticotrope cells will be reviewed to highlight the physiological relevance of a Ca(2+) cAMP interactions in neuroendocrinology.

A novel GABAA alpha 5 receptor inhibitor with therapeutic potential

Novel 2,3-benzodiazepine and related isoquinoline derivatives, substituted at position 1 with a 2-benzothiophenyl moiety, were synthesized to produce compounds that potently inhibited the action of GABA on heterologously expressed GABAA receptors containing the alpha 5 subunit (GABAA α5), with no apparent affinity for the benzodiazepine site. Substitutions of the benzothiophene moiety at position 4 led to compounds with drug-like properties that were putative inhibitors of extra-synaptic GABAA α5 receptors and had substantial blood-brain barrier permeability. Initial characterization in vivo showed that 8-methyl-5-[4-(trifluoromethyl)-1-benzothiophen-2-yl]-1,9-dihydro-2H-[1,3]oxazolo[4,5-h][2,3]benzodiazepin-2-one was devoid of sedative, pro-convulsive or motor side-effects, and enhanced the performance of rats in the object recognition test. In summary, we have discovered a first-in-class GABA-site inhibitor of extra-synaptic GABAA α5 receptors that has promising drug-like properties and warrants further development.

Synthesis and in vitro evaluation of oxindole derivatives as potential radioligands for 5-HT(7) receptor imaging with PET.

The most recently discovered serotonin (5-HT) receptor subtype, 5-HT(7), is considered to be associated with several CNS disorders. Noninvasive in vivo positron emission tomography (PET) studies of cerebral 5-HT(7) receptors could provide a significant advance in the understanding of the neurobiology and eventual dysfunctions of the 5-HT(7) receptor. To date, no appropriate 5-HT(7) receptor PET ligand has been developed. Here, we modified known 5-HT(7) selective phenylpiperazinyl-butyloxindole derivatives so that they may be labeled either with carbon-11 or fluorine-18. A set of potential 5-HT(7) ligands for PET molecular imaging was successfully synthesized. Two compounds (10 and 14) were tested against a range of targets. Both compounds display a promising in vitro profile with respect to PET imaging of the 5-HT(7) receptor in thalamic regions.

Loop-F of the α-subunit determines the pharmacologic profile of novel competitive inhibitors of GABAA receptors

ABSTRACT The neurotransmitter &ggr;‐amino butyric acid (GABA) has a fundamental role in CNS function and ionotropic (GABAA) receptors that mediate many of the actions of GABA are important therapeutic targets. This study reports the mechanism of action of novel GABAA antagonists based on a tricyclic oxazolo‐2,3‐benzodiazepine scaffold. These compounds are orthosteric antagonists of GABA on heteropentameric GABAA receptors of &agr;x&bgr;2&ggr;2 configuration expressed in HEK293 cells. In silico modelling predicted that the test compounds docked in the GABA binding‐pocket and would interact with amino‐acid residues in the &agr;‐ and &bgr;‐subunit interface that are known to be important for the binding of GABA. Intriguingly, optimal docking also required an interaction with the non‐conserved amino‐terminal segment of Loop‐F of the &agr;–subunit. Testing of a compound with altered regiochemistry of the oxazolone moiety supported the model with respect to the conserved GABA‐interacting residues in vitro as well as in vivo. The prediction regarding loop‐F was examined by replacing the amino‐terminal variable segment of loop‐F of the &agr;5‐subunit with the corresponding residues in the &agr;1‐ and &agr;2‐subunits. When tested with the novel inhibitors, the receptors formed by the modified &agr;5‐subunits displayed the pharmacologic phenotype of the source of loop‐F. In summary, these data show that the variable amino‐terminal segment of loop‐F of the &agr;‐subunit determines the pharmacologic selectivity of the novel tricyclic inhibitors of GABAA receptors.

Optical Waveguide Lightmode Spectroscopic Techniques for Investigating Membrane-Bound Ion Channel Activities

Optical waveguide lightmode spectroscopic (OWLS) techniques were probed for monitoring ion permeation through channels incorporated into artificial lipid environment. A novel sensor set-up was developed by depositing liposomes or cell-derived membrane fragments onto hydrophilic polytetrafluoroethylene (PTFE) membrane. The fibrous material of PTFE membrane could entrap lipoid vesicles and the water-filled pores provided environment for the hydrophilic domains of lipid-embedded proteins. The sensor surface was kept clean from the lipid holder PTFE membrane by a water- and ion-permeable polyethylene terephthalate (PET) mesh. The sensor set-up was tested with egg yolk lecithin liposomes containing gramicidin ion channels and with cell-derived membrane fragments enriched in GABA-gated anion channels. The method allowed monitoring the move of Na+ and organic cations through gramicidin channels and detecting the Cl–-channel functions of the (α5β2γ2) GABAA receptor in the presence or absence of GABA and the competitive GABA-blocker bicuculline.