Antipyretic and platelet antiaggregating effects of nimesulide.

Nimesulide strongly inhibited ex vivo platelet aggregation in guinea-pigs after both single and repeated (once daily for 5 days) oral dosing, irrespective of the aggregating agent used (adenosine diphosphate, arachidonic acid or collagen). Its potency was consistently greater than that shown by either ticlopidine or acetylsalicylic acid. In both oral and rectal administration, nimesulide proved to be more active and longer lasting than paracetamol in inhibiting fever induced in rats injected subcutaneously with brewer's yeast.

Cardiovascular activities of the new potent and long-lasting antihypertensive calcium entry blocker (+-)-3-ethyl,5-methyl,2- ([2-(formylamino)-ethyl]- thiomethyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicar box ylate.

BBR 2160 ((+-)3-ethyl,5-methyl,2-([2-(formylamino)-ethyl]- thiomethyl)-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarb oxy late, CAS 118587-22-7) is a new calcium entry blocker (CEB) which completely displaces 3H-nitrendipine from binding sites, is 10 times more potent than amlodipine (A) and equiactive with nifedipine (N). On the rat aorta contracted by 10 mmol/l Ca++, or 45 mmol/l K+, BBR 2160 shows higher CEB activity than N and A, achieving the maximum effect on voltage operated channels-induced contractions in 6 h, while N takes about 2 h. BBR 2160, N and A negatively affect the chronotropism on spontaneously beating, and inotropism on electrically driven guinea pig atria, respectively. In vitro BBR 2160 has marked vasoselectivity. Administered orally to conscious hypertensive rats (SHR) and renal hypertensive dogs (RHD), it caused a dose-dependent reduction in systolic blood pressure with a relatively slow onset, peak effect at 3-6 h and duration over 6 h. BBR 2160 and A have more pronounced activity on SHR than on normotensive rats (NR) (ED20 NR/SHR 3.3 for both compounds), while the antihypertensive and hypotensive activities of N are in the same dose-range (ED20 NR/SHR 1.3). No tolerance develops to the antihypertensive effects of BBR 2160 after five days' dosing up to 3.2 mg/kg in SHR and 1 mg/kg in RHD. In instrumented conscious normotensive dogs BBR 2160, N and A mostly lower diastolic blood pressure and total peripheral resistance, and do not increase total oxygen consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations of GABA-A and dopamine D-2 brain receptors in dogs with portal-systemic encephalopathy.

The binding characteristics of gamma-aminobutyric acid-A (GABA-A) receptors and the kinetic characteristics of the target enzyme of GABA synthesis in nerve terminals, glutamic acid decarboxylase (GAD), were studied in a dog model of portal-systemic encephalopathy obtained by porta-caval shunt performed in dimethylnitrosamine pretreated animals. Furthermore the properties of dopamine receptors and the levels of catecholamines of encephalopathic dogs were investigated. The mild stage of encephalopathy was characterized by an up-regulation of the inhibitory GABA-A receptors probably related to a decrese of GABA in nerve terminals since GAD was decreased and by a slight decrease of catecholamines and by an increased synthesis of octopamine associated with a decreased affinity of dopamine receptors. In the severe stage there was a selection of high affinity GABA-A receptors with an increased number of benzodiazepine recognition sites which were supersensitive to GABA stimulation, a decreased number of Dopamine D-2 receptors and a marked reduction of catecholamines. These data seem to suggest that the neurological disturbances of experimental portal-systemic encephalopathy might be the result of an imbalance between inhibitory and excitatory systems leading to a prevalence of the first one.

Synthesis and biological evaluation of substituted benzo[h]cinnolinones and 3H-benzo[6,7]cyclohepta[1,2-c]pyridazinones: higher homologues of the antihypertensive and antithrombotic 5H-indeno[1,2-c]pyridazinones.

Several substituted benzo[h]cinnolinones 3 and 3H-benzo[6,7]cyclohepta[1,2-c]pyridazinones 4, which were designed as less rigid congeners of 5H-indeno[1,2-c]pyridazinones 2, were synthesized and tested as antihypertensive, inotropic, antithrombotic, antiinflammatory, and antiulcer agents. While the seven-membered ring derivatives displayed only antithrombotic properties, which were comparable to that of acetylsalicylic acid, most of the benzo[h]cinnolinones exhibited significant antihypertensive, inotropic, and antithrombotic properties. In this respect, the 8-amino (3b) and 8-acetylamino (3c) together with the 4,4a-dehydro analogue of 3c (11) were found to possess the most potent and long-lasting antihypertensive activity. In particular, the dextro isomer of 3c was more active than the racemic form, with lower tachycardiac effects. Unlike the lower homologues 2, none of the compounds showed significant antiinflammatory or antiulcer activity.

Synthesis and pharmacological study of 5-aryl-6-methyl-4,5-dihydro-pyridazin-3(2H)ones and related 5-aryl-6-methyl-pyridazin-3(2H)ones.

New 5-aryl-6-methyl-4,5-dihydropyridazin-3(2H)ones (III) and related 5-aryl-6-methyl-pyridazin-3(2H)ones (IV) were synthesized in order to evaluate their pharmacological profile in comparison with that of the known class of antihypertensive and platelet aggregation inhibitors 5-methyl-6-aryl-4,5-dihydropyridazin 3(2H)ones (I). Though none of the tested derivatives was found to possess the antihypertensive potency of the reference compounds, some of them displayed significant antithrombotic and antiulcer properties. In particular, 5(p. acetylaminophenyl)-6-methyl-pyridazin-3-one (IV c) was found highly effective (ED50 = 1.2 mg/kg) in inhibiting indomethacin-induced ulcers.

New congeners of antihypertensive and antithrombotic 7-amino or 7-acetyl-aminosubstituted-4,4a-dihydro-5H-indeno (1,2-c)pyridazin-3-ones.

New congeners of the antihypertensive and antithrombotic 7-amino-(I b) and 7-acetylamino-4,4a-dihydro-5H-indeno(1,2-c)pyridazin-3-one (I c) have been synthesized and evaluated pharmacologically. Compounds (I k) (R = 7-NHCH3), (I l) (R = 7-N(CH3)COCH3) and (I m) (R = 7-N(CH3)COC2H5) exhibited an antihypertensive effect similar to that of (I b) and (I c), though short lasting. The antithrombotic activity of six compounds was found comparable to or higher than that of acetylsalicilic acid. In particular, (I l) and (I m) fully protected mice against thrombosis, as did the reference compound (I c).

Antihypertensive and antithrombotic activities of 6-(substituted phenyl)-5-hydroxymethyl-4,5-dihydro-3(2H)pyridazinones.

The synthesis of a series of 6-(4R-phenyl)-5-hydroxymethyl-4,5-dihydro-3(2H)pyridazinones is reported. The compounds were evaluated for their oral antihypertensive activity in rats and some of them [(V b), R = NH2] and [(V c), R = NHCOCH3] were found to induce a high decrease in systolic blood pressure. Moreover all the compounds displayed an antithrombotic activity comparable to, or greater than, that of ASA.

Conformationally restricted congeners of hypotensive and platelet aggregation inhibitors: 6-aryl-5-methyl-4,5-dihydro-3(2H)-pyridazinones derived from 5H-indeno[1,2-c]pyridazine.

A number of 7-amino and 7-acylamino substituted 4,4a-dihydro-5H-indeno[1,2-c]pyridazin-3-ones have been synthesized as rigid congeners of hypotensive 6-aryl-5-methyl-4,5-dihydro-3(2H)-pyridazinones and tested as antihypertensive, antithrombotic, antiulcer, and antiinflammatory agents. Unlike the previously described 7-cyano derivative, which displayed only antiinflammatory action, the new series exhibited significant antihypertensive and antithrombotic properties. In this respect, the 7-amino (2b) and the 7-acetylamino (2c) derivatives were found to be the most potent and long lasting in reducing the blood pressure in spontaneously hypertensive rats and in protecting mice from the induction of thrombosis. These compounds, as well as the 7-(2-chloropropionyl) derivative 2d, also exhibited antiinflammatory activity; in addition, 2c,d were highly effective in inhibiting indomethacin-induced ulcers in the rat.

Opiate receptors and beta-endorphin levels in brain areas of dogs with portal-systemic encephalopathy.

Clinical observation has indicated a supersensitivity to morphine in patients with hepatic encephalopathy. With the aim of clarifying the issue, radioreceptor binding studies of opiate receptors were performed in frontal cortex and hypothalamus of 6 dogs with mild portal-systemic encephalopathy induced by chronic treatment with dimethylnitrosamine followed by porto-caval shunt end-to-side. beta-Endorphin assays were performed in the same areas with radioimmunoassay. Opiate receptors labeled with [3H]naloxone in both areas showed a significant increase in the receptor densities (Bmax) without changes in the dissociation constant (KD). In parallel beta-endorphin levels showed a decline during the development of encephalopathy in both areas. The increased densities of opiate receptors in the mild stage of encephalopathy may explain the supersensitivity to morphine in patients with liver diseases.