In an effort to develop antihypertensive agents with peripheral vasodilator activity, a series of 40 novel 3-hydrazino-5-phenyl-1,2,4-triazines (II) were synthesized and evaluated in the spontaneously hypertensive rat assay (SHR assay). Based on the performance of the structurally related standard, hydralazine (I), 15 triazines were active. Thirteen of these hypotensive triazines possessed LD50 values in the mouse greater than I (LD50 = 100 mg/kg); only one active triazine had an LD50 value greater than 300 mg/kg (11d). Four asymmetric triazines had moderate antihypertensive activity and LD50 values greater than 300 mg/kg (6b, 7c, 8f, and 9g). Based on the relationship between toxicity and antihypertensive activity, three triazines (8f, 9g, and 11d) were chosen for dose-responses studies in the SHR assay. None were as efficacious as I, but all three were less toxic, resulting in similar therapeutic indices relative to I.
The effect of structural change on the biological activity of a series of imidazothiazoles and thiazolobenzimidazoles is described. It was found that compounds with polar substituents at the 2 or 3 position of the ring system are less acutely toxic while maintaining antiinflammatory activity. Other structural changes, such as the incorporation of a gem-dimethyl substituent in the 6 position, increase acute toxicity and eliminate antiinflammatory activity. The compound with the best activity/toxicity ratio contains an alkyl sulfonyl substituent on the thiazole ring. The thiazolobenzimidazole analogues are more potent than the imidazole analogues.
The synthesis of a series of 5,6-diarylpyridazinones is described. Some members of this series display an antihypertensive effect in both the spontaneously hypertensive rat (SHR) model and the deoxycorticosteroid (DOCA) model of hypertension. The most potent compounds in the series have halogen substituents on the 5,6-diphenyl rings, a beta-substituted alkyl group at the 2 position of the ring, and acetyl or cyano substituent at the 4 position.
Flutamide (FTA), an anti-androgenic compound, inhibited the effects of methyltestosterone (MT) on the weight of the ventral prostate, seminal vesicles and levator ani in male castrate mice. Castration prevented the development of aggressive behavior in mice isolated for 3 weeks. While chronic administration of MT to castrate isolated mice returned the incidence of fighting behavior to control values, chronic administration of FTA + MTdid not significantly reduce the incidence of fighting as compared to castrate + MT values. These results suggest that the mechanism for androgen stimulation of secondary sex organ weight may differ from that involved in the development and maintenance of aggression resulting from isolation.
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