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.

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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.