60478-25-3

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We have recently shown that an aryloaminopyridazine derivarive of GABA, SR 95103 , is a selective and competitive GABA-A receptor antagonist.In order to further explore the structural requirements for GABA receptor affinity, we synthesized a series of 38 compounds by attaching various pyridazinic structures to GABA or GABA-like side chains.Most of the compounds displaced GABA from rat brain membranes.All the active compounds antagonized the GABA-elicited enhancement of diazepam binding, strongly suggesting that all these compounds are GABA-A receptor antagonists.None of the compounds that displaced GABA from rat brain membranes interacted with other GABA recognition sites (GABA-B receptor, GABA uptake binding site, glutamate decarboxylase, GABA-transaminase).They did not interact with the Cl- ionophore associated with the GABA-A receptor and did not interact with the benzodiazepine, strychnine, and glutamate binding sites.Thus these compounds appear to be specific GABA-A receptor antagonists.In terms of structure-activity, it can be concluded that a GABA moiety bearing a positive charge is necessary for optimal GABA-A receptor recognition.Additional binding sites are tolerated only if they are part of a charge-delocalized amidinic or guanidinic system.If this delocalization is achieved by linking a butyric acid moiety to the N(2) nitrogen of a 3-aminopyridazine, GABA-antagonistic character is produced.The highest potency (ca.250 times bicuculline) was observed when an aromatic ? system, bearing electron-donating substituents, was present on the 6-position of the pyridazine ring.

This disclosure describes novel alkyl 3-[6-(aryl)-3-pyridazinyl]-carbazates useful as hypotensive agents in mammals. SP CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of our copending application Ser. No. 692,254, filed June 3, 1976 now abandoned, which in turn is a continuation-in-part of our abandoned application Ser. No. 552,024, filed Feb. 24, 1975 now abandoned.

This disclosure describes compositions of matter useful as anxiolytic agents and the method of meliorating anxiety in mammals therewith; the active ingredients of said compositions of matter being certain substituted 6-phenyl-1,2,4-triazolo[4,3-b]pyridazines or the pharmacologically acceptable acid-addition salts thereof.

This disclosure describes novel substituted 6-phenyl-1,2,4-triazolo[4,3-b]pyridazines useful as hypotensive agents.