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A new process for obtaining dibenzo[c,f][1,2,5]thiadiazepines (DBTDs) and their effects on GABAA receptors of guinea pig myenteric neurons are described. Synthesis of DBTD derivatives began with two commercial aromatic compounds. An azide group was obtained after two sequential reactions, and the central ring was closed via a nitrene to obtain the tricyclic sulfonamides (DBTDs). Whole-cell recordings showed that DBTDs application did not affect the holding current but inhibited the currents induced by GABA (IGABA), which are mediated by GABAA receptors. These DBTDs effects reached their maximum 3 min after application and were: (i) reversible, (ii) concentration-dependent (with a rank order of potency of 2c = 2d > 2b), (iii) mediated by a non-competitive antagonism, and (iv) only observed when applied extracellularly. Picrotoxin (which binds in the channel mouth) and DBTDs effects were not modified when both substances were simultaneous applied. Our results indicate that DBTD acted on the extracellular domain of GABAA channels but independent of the picrotoxin, benzodiazepine, and GABA binding sites. DBTDs used here could be the initial model for synthesizing new GABAA receptor inhibitors with a potential to be used as antidotes for positive modulators of these receptors or to induce experimental epilepsy. © 2013 by the authors.
Dibenzo[1,2,5]thiadiazepines are non-competitive GABAA receptor antagonists
4 aminobutyric acid, 28805-76-7, 56-12-2; GABA-A Receptor Antagonists; Receptors, GABA-A; Thiadiazines; gamma-Aminobutyric Acid, 56-12-2
Biological activity; Dibenzothiadiazepines; Electrophysiology; Enteric neurons; GABAA receptor antagonists; Neurochemistry; Patch clamp 4 aminobutyric acid; 4 aminobutyric acid A receptor; 4 aminobutyric acid A receptor blocking agent; 4 aminobutyric acid receptor; thiadiazine derivative; animal; article; cell culture; cytology; drug effect; female; guinea pig; IC 50; male; membrane potential; metabolism; myenteric plexus; patch clamp; primary cell culture; synthesis; Animals; Cells, Cultured; Female; GABA-A Receptor Antagonists; GABAergic Neurons; gamma-Aminobutyric Acid; Guinea Pigs; Inhibitory Concentration 50; Male; Membrane Potentials; Myenteric Plexus; Patch-Clamp Techniques; Primary Cell Culture; Receptors, GABA-A; Thiadiazines
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