Ritanserin

Dual activities of ritanserin and R59022 as DGKalpha inhibitors and serotonin receptor antagonists.[Pubmed:27974147]

Biochem Pharmacol. 2017 Jan 1;123:29-39.

Diacylglycerol kinase alpha (DGKalpha) catalyzes the conversion of diacylglycerol (DAG) to phosphatidic acid (PA). Recently, DGKalpha was identified as a therapeutic target in various cancers, as well as in immunotherapy. Application of small-molecule DGK inhibitors, R59022 and R59949, induces cancer cell death in vitro and in vivo. The pharmacokinetics of these compounds in mice, however, are poor. Thus, there is a need to discover additional DGK inhibitors not only to validate these enzymes as targets in oncology, but also to achieve a better understanding of their biology. In the present study, we investigate the activity of Ritanserin, a compound structurally similar to R59022, against DGKalpha. Ritanserin, originally characterized as a serotonin (5-HT) receptor (5-HTR) antagonist, underwent clinical trials as a potential medicine for the treatment of schizophrenia and substance dependence. We document herein that Ritanserin attenuates DGKalpha kinase activity while increasing the enzyme's affinity for ATP in vitro. In addition, R59022 and Ritanserin function as DGKalpha inhibitors in cultured cells and activate protein kinase C (PKC). While recognizing that Ritanserin attenuates DGK activity, we also find that R59022 and R59949 are 5-HTR antagonists. In conclusion, Ritanserin, R59022 and R59949 are combined pharmacological inhibitors of DGKalpha and 5-HTRs in vitro.

Ritanserin-sensitive receptors modulate the prosocial and the anxiolytic effect of MDMA derivatives, DOB and PMA, in zebrafish.[Pubmed:27506653]

Behav Brain Res. 2016 Nov 1;314:181-9.

Little is known about the pharmacological effects of amphetamine derivatives. In the present study, the effect on social preference and anxiety-like behavior of 2,5-dimetoxy-4-bromo-amphetamine hydrobromide (DOB) and para-methoxyamphetamine (PMA), in comparison with 3,4 methylenedioxymethamphetamine (MDMA) was investigated in zebrafish, an emerging model to study emotional behavior in an inexpensive and quick manner. DOB (0.05-2mg/kg), PMA (0.0005-2mg/kg) or MDMA (0.25-20mg/kg), given i.m. to adult zebrafish, progressively increased the time spent in the proximity of nacre fish picture in a social preference test. However, high doses were ineffective. Similarly, in the novel tank diving and light-dark tests the compounds elicited a progressive anxiolytic effect in terms of time spent in the upper half of the tank and in the light compartment, respectively. All the above effects were interpolated by symmetrical parabolas. The 5-HT2A/C antagonist Ritanserin (0.025-2.5mg/kg) in association with the maximal effective dose of MDMA, DOB and PMA blocked both the social and anxiolytic effect. Taken together these findings demonstrate for the first time the prosocial and anxiolytic properties of DOB and PMA and focus on the mechanisms of their action through the serotonergic-like system suggesting a potential clinical application.

The combination of agomelatine and ritanserin exerts a synergistic interaction in passive avoidance task.[Pubmed:25394903]

Hum Exp Toxicol. 2015 Aug;34(8):787-95.

Agomelatine is a potent agonist at melatonergic 1 and 2 (MT1 and MT2) receptors and an antagonist at serotonin-2C (5HT-2C) receptors. It was suggested that psychotropic effects of agomelatine is associated with its melatonergic and serotonergic effects. In this study, we aimed to evaluate the effects of agomelatine alone or in combination with Ritanserin (5HT-2A/2C antagonist) on memory and learning. Male Balb-C mice (25-30 g) were used, and all drugs and saline were administrated by intraperitoneal (i.p.) route 30 min prior to evaluating retention time. Whilst agomelatine was administered at the doses of 1, 10 and 30 mg/kg, Ritanserin was administered at the doses of 0.1, 1 and 10 mg/kg. To evaluate memory function, passive avoidance test was used. On the first day, acquisition time and on the second day (after 24h), retention time of mice were recorded. To evaluate the synergistic activity, only the least doses of agomelatine and Ritanserine were used, that is, 1 and 0.1 mg/kg, respectively. Scopolamine (1 mg/kg) was used as a reference drug, so it was combined with drug groups. Our results show that 5HT-2A/2C receptor antagonist Ritanserin (1 and 4 mg/kg, i.p.) and agomelatine (10 and 30 mg/kg, i.p.) improve memory deficit induced by scopolamine, whilst a synergistic interaction is observed between Ritanserin and agomelatine (0.1 mg/kg and 1 mg/kg, i.p., respectively) when they were administered at their ineffective doses. According to our findings, we concluded that agomelatine improves memory deficit and thus improves the effect of agomelatine arises from its 5HT-2C receptor antagonist activity.

Syntheses and 5-HT2 antagonist activity of bicyclic 1,2,4-triazol-3(2H)-one and 1,3,5-triazine-2,4(3H)-dione derivatives.[Pubmed:1732528]

J Med Chem. 1992 Jan;35(1):189-94.

A series of bicyclic 1,2,4-triazol-3(2H)-one and 1,3,5-triazine-2,4(3H)-dione derivatives with a 4-[bis(4-fluoro-phenyl)methylene]piperidine or 4-(4-fluorobenzoyl)piperidine group has been prepared and tested for 5-HT2 and alpha 1 receptor antagonist activity. Among the compounds prepared, 2-[2-[4-[bis(4-fluorophenyl)methylene]-piperidin-1-yl]ethyl]- 5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyridin-3(2H)-one (7b) had the most potent 5-HT2 antagonist activity, which was greater than Ritanserin (2), while 7b did not show alpha 1 antagonist activity in vivo. The central 5-HT2 receptor antagonism was approximately 1/30 that of 2 when tested for the ability to block head twitches induced by 5-hydroxytryptophan. Compound 21b, 3-[2-[4-(4-fluorobenzoyl)piperidin-1-yl]ethyl]-6,7,8,9-tetrahydro- 2H- pyrido[1,2-a]-1,3,5-triazine-2,4(3H)-dione also displayed potent 5-HT2 antagonist activity. The compound had moderate alpha 1 receptor antagonism, and the potency inhibiting head twitches was about one-third that of ketanserin (1). These results indicate that 5,6,7,8-tetrahydro-1,2,4-triazolo[4,3-a]pyrimidin-3(2H)-one and 6,7,8,9-tetrahydro-2H-pyrido-[1,2-a]-1,3,5-triazine-2,4(3H)-dione ring systems are useful components of 5-HT2 antagonists.

Pharmacology of potent and selective S2-serotonergic antagonists.[Pubmed:2412048]

J Cardiovasc Pharmacol. 1985;7 Suppl 7:S2-11.

Ketanserin is the prototype of a new series of serotonergic antagonists that competitively and selectively block 5-hydroxytryptamine (S2) serotonergic receptors. Ketanserin and its analogues antagonize the events mediated by this receptor, i.e., serotonin-induced vasoconstriction, bronchoconstriction, and platelet aggregation, irrespective of whether serotonin acts directly or amplifies the effect of vasoconstrictors or platelet aggregating agents. The antagonism is pure because compounds such as ketanserin are devoid of agonistic activity. The actions of ketanserin are mainly peripheral, whereas other members of the series, e.g., Ritanserin, act on the brain and are potent antagonists of lysergic acid diethylamide and other centrally acting serotonomimetic drugs. The different pharmacological profiles of the new S2-serotonergic antagonists and the evidence already available on their clinical effects prompt a further exploration of these agents in a large range of cardiovascular and other diseases.

Receptor-binding properties in vitro and in vivo of ritanserin: A very potent and long acting serotonin-S2 antagonist.[Pubmed:2860558]

Mol Pharmacol. 1985 Jun;27(6):600-11.

In vitro and in vivo receptor-binding properties of the new serotonin antagonist, Ritanserin, are reported. In in vitro binding assays, Ritanserin shows high affinity binding to serotonin-S2 sites in rat frontal cortex tissue: IC50 = 0.9 nM without drug preincubation and 0.3 nM with 30-min drug preincubation; IC50 values for histamine-H1, dopamine-D2, and adrenergic-alpha 1 and -alpha 2 sites were 39-, 77-, 107-, and 166-fold higher, and at up to 1 microM, the drug did not bind to serotonin-S1 sites. In in vitro assays, Ritanserin dissociated very slowly from serotonin-S2 (t1/2 = 160 min) and histamine-H1 sites (t1/2 = 77 min) and rapidly from dopamine-D2 sites (t1/2 = 11 min). Half-times of dissociation from adrenergic-alpha 1 and -alpha 2 sites were 18 and 26 min. The inhibition by Ritanserin of [3H]ketanserin binding was found to be partially noncompetitive and the inhibitory potency increased with drug preincubation. Due to the slow dissociation of Ritanserin from the serotonin-S2 sites, the drug cannot be displaced completely by [3H]ketanserin. In contrast, inhibition by Ritanserin of [3H]haloperidol binding to dopamine-D2 sites in rat striatum was fully competitive, in agreement with the rapid dissociation of the drug from the latter sites. In ex vivo binding assays using brain areas of rats and guinea pigs treated subcutaneously with Ritanserin, occupation of serotonin-S2 sites was observed at very low dosage (50% occupation at 0.08-0.1 mg/kg) and sites remained occupied during a prolonged time period (greater than 70% occupation up to 48 hr after 2.5 mg/kg Ritanserin). Histamine-H1 receptor sites in guinea pig cerebellum became occupied at dosages 25-fold higher than the dosage producing occupation of frontal cortical serotonin-S2 sites. Dopamine-D2 sites in rat striatum and cortical adrenergic-alpha 1 sites became only slightly occupied (less than 20%) at higher dosages and the effect was not dose-dependent. Adrenergic-alpha 2 sites were not occupied up to doses of 160 mg/kg given subcutaneously. In vivo binding assays using [3H]spiperone confirmed the occupation of frontal cortical serotonin-S2 sites following low dosage of Ritanserin and a minor occupation of striatal dopamine-D2 sites. Levels of dopamine and serotonin and their metabolites remained unchanged in brain areas of rats orally treated with Ritanserin up to dosages of 40 mg/kg. At 160 mg/kg, there seemed to be a slight reduction in dopamine and serotonin content.(ABSTRACT TRUNCATED AT 400 WORDS)

Ritanserin (R 55667) is a highly potent, relatively selective, orally active, long acting antagonist of 5-HT2 receptor, with an IC50 of 0.9 nM, less active on Histamine H1, Dopamine D2, Adrenergic α1, Adrenergic α2 receptors.

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