Antihyperalgesic effects of a novel muscarinic agonist (LASSBio-873) in spinal nerve ligation in rats.

New chemicals or adjuvants with analgesic effects on chronic pain are needed and clinically relevant due to the limited number of effective compounds that possess these characteristics. LASSBio-873, a pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivative, activates muscarinic cholinergic receptors and has potent analgesic effects on acute and inflammatory pain. The present study evaluated the therapeutic and prophylactic effects of oral administration of LASSBio-873 in a spinal nerve ligation (SNL) model of chronic peripheral nerve injury. LASSBio-873 (100 mg/kg) inhibited the development of thermal hyperalgesia and mechanical allodynia when administered once daily for 7 consecutive days after SNL surgery and reversed these symptoms. LASSBio-873 treatment did not alter rat behaviour in open field testing measured during the first 24 h after administration and again after 7 continuous days administration. The analgesic effect of LASSBio-873 was inhibited by intrathecal methoctramine, an M2 receptor antagonist, implicating the muscarininc M2 receptor signalling pathway in the drug's action. These results reinforce the potential of LASSBio-873 as a possible prototype for the development of more effective alternatives for the treatment of neuropathic pain.

Sedative and anticonvulsant activities of methanol extract of Dorstenia arifolia in mice.

ETHNOPHARMACOLOGICAL RELEVANCE: Dorstenia arifolia is a plant that has been used in the folk medicine to produce hypnotic, sedative and ansiolitic effects but the pharmacological properties have not yet been studied. In addition, the smoke of its rhizome is reputed to induce lethargic sensation. AIMS OF THE STUDY: The present study investigated possible activities of the methanol extract (ME) of Dorstenia arifolia rhizome on the central nervous system (CNS). MATERIALS AND METHODS: ME was tested for sedative, hypnotic and anticonsulsant effects using locomotor activity evaluation, pentobarbital-induced sleeping time and pentylenetetrazol (PTZ)-induced convulsion, respectively. RESULTS: Intraperitoneal administration of ME (10 and 50mg/kg) significantly decreased locomotor activity from 205.2+/-25.6 movements/min (DMSO) to 112.1+/-18.4 (P<0.05) and 114.9+/-16.9 (P<0.05), respectively. Flumazenil (10 mg/kg), an antagonist of GABA(A) receptor, prevented the ME-induced sedation. Treatment with ME (50mg/kg) significantly increased the duration of pentobarbital-induced sleeping time from 41.0+/-2.3 to 57.9+/-2.9 min (P<0.05). The latencies to seizures after intraperitoneal injection of PTZ was recorded and compared between groups. ME promoted a significant protection of PTZ-induced seizures and mortality in a dose-dependent manner. CONCLUSIONS: Our findings indicate that ME of Dorstenia arifolia rizhome has pronounced central effects, and that the sedative and anticonvulsant activities may be related to a facilitation of the GABAergic transmission.

Microwave-assisted synthesis and structure-activity relationships of neuroactive pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivatives.

We described herein the optimization of the synthetic methodology exploited to obtain the pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine sedative prototype 1a and novel analogues designed by successive molecular simplifications. By applying microwave irradiation during the hetero Diels-Alder key-step to obtain the heterotricyclic scaffold, under solvent-free conditions, we were able to obtain the desired compounds in drastically shorter times and better yields. Additionally, in vivo evaluation of the sedative effects of these heterocyclic derivatives showed that 1a and the novel structurally-related analogue 1e were the most efficient compounds to impair the locomotor activity in mice at the dose of 10micromol/kg.

Sedation and antinociception induced by a new pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivative (LASSBio-873) is modulated by activation of muscarinic receptors.

New substances designed for the treatment of anxiety have previously been synthesized, which resulted in the identification of four new pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine derivatives structurally designed by using zolpidem as lead compound. Among them, LASSBio-873 was the most potent to produce analgesic, sedative and hypnotic effects. Thus, we investigated the possible mechanisms involved in LASSBio-873-induced sedation, as well as its effects on different models of inflammatory pain. LASSBio-873 (4 mg/kg) reduced locomotor activity of mice in the open field test from 205.2+/-25.6 to 87.6+/-16.2 movements/min. Atropine, a non-selective muscarinic antagonist, prevented the LASSBio-873-induced sedation and increased locomotor activity to 192.9+/-30.2 movements/min. In the formalin test, LASSBio-873 (4 mg/kg) significantly reduced the duration of nociceptive behavior during the inflammatory phase, reducing the control reactivity from 197.6+/-14.5s to 84.4+/-10.3s. Carrageenan reduced the latency for the animal reaction from 5.1+/-0.2s (control) to 2.1+/-0.3s which was completely reverted by LASSBio-873 (6 mg/kg) to 5.6+/-0.6s. Atropine prevented the LASSBio-873-induced antinociceptive and antihyperalgesic activities, indicating the interference of the cholinergic system. LASSBio-873 is a novel prototype of drug that modulates muscarinic activity and could be used for neuropsychiatric and cognitive disorders and other conditions associated to acute and chronic pain.

Sedative-hypnotic profile of novel isatin ketals.

Isatin (1H-indol-2,3-dione) is an endogenous compound found in many tissues and fluids. Isatin and its derivatives exert pharmacological effects on the central nervous system, including anxiogenic, sedative and anticonvulsant activities. Two new groups of isatin derivatives were synthesized (nine dioxolane ketals and nine dioxane ketals) and studied for their sedative, hypnotic and anesthetic effects using pentobarbital-induced sleeping time, locomotor activity evaluation and intravenous infusion. The dioxolane ketals were more potent than dioxane ketals for inducing sedative-hypnotic states, causing up to a three-fold increase in pentobarbital hypnosis. The dioxolane ketals produced sedation, demonstrated by decreased spontaneous locomotor activity in an open field. Hypnosis and anesthesia were observed during intravenous infusion of 5'-chlorospiro-[1,3-dioxolane-2,3'-indolin]-2'-one (T3) in conscious Wistar rats. Complete recovery from hypnosis and anesthesia required 39.1+/-7.3 and 6.8+/-2.4 min, respectively. Changes in hemodynamic parameters after infusion of 5.0 mg/kg/min were minimal. These findings suggest that these new isatin derivatives represent potential candidates for the development of new drugs that act on the central nervous system and may lead to a new centrally acting anesthetic with no toxic effects on the cardiovascular or respiratory systems.