piperidines and Mydriasis

1. Antagonistic properties of OPC-28326 ([4-(N-methyl-2-phenylethylamino)-1-(3,5-dimethyl-4-propionyl-aminobenzoyl)] piperidine hydrochloride monohydrate), a selective peripheral vasodilator, were investigated by analysing the data from functional studies in various tissues from the rat and binding studies of the drug to alpha(2)-adrenoceptor subtypes. 2. Using a human recombinant receptor and rat kidney cortex, we found that OPC-28326 displays affinities to alpha(2A)-, alpha(2B)- and alpha(2C)-adrenoceptors with K(i) values of 2040, 285, and 55 nM, respectively. The K(i) values of yohimbine for alpha(2A)-, alpha(2B)-, and alpha(2C)-adrenoceptors were 3.0, 2.0 and 11.0 nM, respectively. 3. B-HT 920, an alpha(2)-adrenoceptor agonist, produced a pressor response via peripheral postsynaptic alpha(2)-adrenoceptor stimulation (thought to be an alpha(2B)-subtype) in a reserpine-pretreated pithed rat preparation. OPC-28326 (3 - 30 mg kg(-1), i.v.) and yohimbine (0.3 - 3 mg kg(-1), i.v.) caused dose-dependent rightward shift in the pressor dose-response curve induced by B-HT 920. The apparent pA(2) values were 1.55 (0.87 - 2.75, 95% confidence interval) and 0.11 (0.06 - 0.21) mg kg(-1), respectively. The potency of OPC-28326 was about 14 times less than that of yohimbine. 4. Clonidine inhibited the tension developed by electrical stimulation, of the rat vas deferens, by its peripheral presynaptic alpha(2A/D)-adrenoceptor action. OPC-28326 (1 - 100 microM) and yohimbine (10 - 1000 nM) caused a rightward shift in the concentration-response curve of clonidine. The pA(2) values were 5.73 (5.54 - 5.91) and 7.92 (7.84 - 8.01), respectively, providing evidence for a potency of OPC-28326 of about 155 times less than that of yohimbine. 5. Mydriasis was induced by brimonidine via stimulation of central alpha(2A/D)-adrenoceptors in anaesthetized rats. Intravenous OPC-28326 had no effect on this action, even at a very high dose of 10 mg kg(-1) i.v., while yohimbine (0.1 - 0.3 mg kg(-1) i.v.) inhibited mydriasis in a dose-dependent manner, indicating that OPC-28326 was at least 100 times less potent than yohimbine in regard to the anti-mydriatic effect. 6. These data suggest that OPC-28326 preferentially exerts peripheral and postsynaptic antagonistic actions on the alpha(2B)- and alpha(2C)-adrenoceptor subtypes.

Topics: Adrenergic alpha-Antagonists; Aniline Compounds; Animals; Azepines; Binding, Competitive; Blood Pressure; Brimonidine Tartrate; Decerebrate State; Dose-Response Relationship, Drug; In Vitro Techniques; Male; Muscle Contraction; Mydriasis; Piperidines; Quinoxalines; Radioligand Assay; Rats; Rats, Sprague-Dawley; Synaptic Transmission; Vas Deferens; Vasodilator Agents; Yohimbine

With the aim of improving of the efficacy and decreasing the side effects of oxybutynin (1), N-[(tetrahydro-3- or 4-pyridyl)methyl]-, N-(4-piperidyl)-, and N-(3- or 4-piperidylalkyl)-2-hydroxyacetamides (3a-n, 4a-g) and the related carboxamides (3o-r, 4h-k, 13', 17) were synthesized and evaluated for inhibitory activity against urinary bladder rhythmic contraction in rats and for mydriatic activity in rats. Some of these compounds were superior to oxybutynin in both inhibitory activity against bladder contraction and selectivity between inhibitory activity against bladder contraction and mydriatic activity. Among them, N-[(1,2,3,6-tetrahydro-4-pyridyl)methyl]- and N-[(1,2,3,6-tetrahydro-1-methyl-4-pyridyl)methyl]-2-hydroxy-2,2- diphenylacetamide (3e, 3f) exhibited the most potent inhibitory activity against bladder contraction (ED30 = 0.005 and 0.003 mg/kg i.v., respectively). Judging from the effect of 3e on detrusor contraction in vitro in guinea-pigs, it appeared that the inhibitory activity of 3e against bladder contraction in vivo was related mainly to its inhibitory activity against detrusor contraction in vitro induced with carbachol (antimuscarine-like activity). The selectivity (20-fold) of 3e between inhibitory activity against bladder contraction and mydriatic activity was greatly superior to that (0.48-fold) of oxybutynin. Compound 3e was synthesized by debenzylation (method E or F) of the corresponding N-[[1-(4-methoxybenzyl)-tetrahydro-4-pyridyl]methyl] derivative (3k), which was prepared by acylation (method B) of the corresponding (tetrahydro-4-pyridyl)methylamine (7k) or by reduction (method D) of the corresponding pyridinium chloride (14k) with NaBH4.

Topics: Acetamides; Animals; In Vitro Techniques; Mandelic Acids; Muscle Contraction; Muscle, Smooth; Mydriasis; Piperidines; Rats; Urinary Bladder; Urination Disorders

Topics: Adult; Astringents; Diagnosis, Differential; Humans; Male; Mydriasis; Piperidines