Morphine-induced Straub tail reaction in mice treated with serotonergic compounds.

Constitutively active 5-HT receptors have been suggested to contribute to motoneuronal excitability, muscle spasms and spasticity. Accordingly, 5-HT receptor inverse agonists have been demonstrated in pilot experiments to reduce spasticity in animal model of spasticity and patients with spinal cord injuries. Thus, 5-HT receptor inverse agonists may represent a novel class of anti-spasticity agents justifying a search for compounds with robust 5-HT receptor inverse agonist activity either among the existing medications or via a dedicated drug discovery program.