Dimaprit dihydrochloride

Influence of different histamine receptor agonists and antagonists on apomorphine-induced licking behavior in rat.[Pubmed:10980276]

Eur J Pharmacol. 2000 Sep 15;404(1-2):169-74.

The effects of different histamine receptor agonists and antagonists on apomorphine-induced licking behavior in rats were investigated. Subcutaneous (s.c.) injection of various doses of apomorphine (0. 125-1.25 mg/kg) induced licking. The licking response was counted by direct observation and recorded for a 75-min period. Intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) injection of the histamine H(1) or H(2) receptor agonist, HTMT (6-[2-(4-imidazolyl)ethylamino]-N-(4-trifluoromethylphenyl) heptanecarboxamide) (50 and 100 microg per rat), or dimaprit (10 and 15 mg/kg, i.p.), respectively, potentiated apomorphine-induced licking, while the histamine H(3) receptor agonist, imetit (5 and 10 mg/kg, i.p.), reduced the licking response induced by apomorphine. Pretreatment with various histamine receptor antagonists, dexchlorpheniramine (30 and 40 mg/kg, i.p.), diphenhydramine (20, 30 and 40 mg/kg, i.p.), famotidine (30 and 40 mg/kg, s.c.) and ranitidine (20, 30 and 40 mg/kg), reduced apomorphine-induced licking, while thioperamide (5 and 10 mg/kg, i.p.) potentiated the apomorphine effect. The effects of HTMT and dimaprit were blocked by dexchlorpheniramine (20 mg/kg, i.p.) and famotidine (20 mg/kg, s.c.), respectively. The inhibitory effect elicited by imetit on apomorphine-induced licking behavior was also abolished in animals treated with thioperamide (2.5 mg/kg, i.p.). The results suggest that histaminergic mechanisms may be involved in the modulation of apomorphine-induced licking behavior.

Nitric oxide synthase inhibition by dimaprit and dimaprit analogues.[Pubmed:10385230]

Br J Pharmacol. 1999 May;127(2):331-4.

1. The similarity in molecular structure between the histamine H2-agonist dimaprit (3-dimethylamino-propyl-isothiourea) and the endogenous nitric oxide synthase (NOS) substrate L-arginine prompted us to study the effect of dimaprit and some dimaprit analogues on NOS activity. Dimaprit and some of its analogues were tested in an in vitro assay which measures the conversion of [3H]-L-arginine to [3H]-L-citrulline. Dimaprit inhibits rat brain NOS (nNOS) concentration dependently with an IC50 of 49+/-14 microM. 2. Removal of one or both of the methyl groups from the non-isothiourea nitrogen of dimaprit improved nNOS inhibitory properties. Aminopropylisothiourea is the most potent compound (IC50 = 4.1+/-0.9 microM) of the series followed by methylaminopropylisothiourea (IC50 = 7.6 +/- microM). 3. The observed effect of aminopropylisothiourea and methylaminopropyl-isothiourea are probably not due to the compounds themselves but to the corresponding mercaptoalkylguanidines, rearrangement products formed in aqueous solutions. This hypothesis is strengthened by the finding that aminobutylisothiourea is not active since a rearrangement to mercaptobutylguanidine does not occur. 4. Remarkably, nitrosylation of the isothiourea group of dimaprit decreases nNOS inhibitory activity, while nitrosylation of the guanidine analogue of dimaprit increases the inhibition of nNOS activity. 5. The pharmacological profile of dimaprit includes inhibition of nNOS. The nNOS inhibitory activity occurs in the same concentration range as the H2-agonist and H3-agonist activity of this compound.

Dimaprit, (S-[3-(N,N-dimethylamino)propyl]isothiourea). A highly specific histamine H2-receptor agonist. Part 2. Structure-activity considerations.[Pubmed:860674]

Agents Actions. 1977 Mar;7(1):39-43.

Dimaprit, S-[3-(N,N-dimethylamino)propyl]isothiourea, appears to be a highly specific histamine H2-receptor agonist. Further indications of specificity are obtained from chemical considerations. Dimaprit has two basic centres (pKa values respectively 8.23 and 9.23, at 40 degrees) and at pH 7.4 about 5% of the molecules will be present as the monocation analogous to histamine monocation. Chemical comparison suggests that the --N+HMe2 group corresponds to the --N+H3 of histamine, and that the isothiourea group of dimaprit (which can undergo 1,3-prototropic tautomerism) may simulate the imidazole ring of histamine and function as a proton transfer agent at H2 receptors. Simple structural analogues of dimaprit are only weakly active, indicating a high degree of chemical specificity for H2-receptor stimulation; such compounds (e.g. the lower homologue, SK & F 91487) may serve as useful chemical controls when studying the actions of dimaprit.

Dimaprit -(S-[3-(N,N-dimethylamino)prophyl]isothiourea) - a highly specific histamine H2 -receptor agonist. Part 1. Pharmacology.[Pubmed:871093]

Agents Actions. 1977 Mar;7(1):31-7.

S-[3-(N,N-Dimethylamino)propyl]isothiourea (dimaprit), has been shown to be a highly specific histamine H2-receptor agonist. Parallel line assays showed that in vitro at H2-receptors it had approximately 17.5% the activity of histamine on the rat uterus and 71% on the guinea-pig right atrium, with similar maximal responses; it had less than 0.0001% the activity of histamine on H1-receptors. Dimaprit stimulated gastric acid secretion in the rat, dog and cat in which it had, respectively, approximately 19,58 and 400-500% the activity of histamine. In the dog and cat the maximum secretory response to dimaprit was significantly greater than that obtained to histamine. The H2-receptor specificity of dimaprit in causing depressor and vasodilator effects was also demonstrated in the cat, in which it had 18-20% of the H2-receptor activity of histamine. Dimaprit should prove to be a very useful tool in studies examining the role of histamine in physiology and pathology. The absence of marked cardiovascular effects at doses maximal for the stimulation of gastric acid secretion, as seen in the cat studies, could lead to this compound being of value as a diagnostic agent in the measurement of maximal acid secretory capacity.