Veratramine-induced behavior associated with serotonergic hyperfunction in mice

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

Constitutively active 5-HT₂ receptors have been suggested to contribute to motoneuronal excitability, muscle spasms and spasticity. Accordingly, 5-HT_2C 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_2C receptor inverse agonists may represent a novel class of anti-spasticity agents justifying a search for compounds with robust 5-HT_2C receptor inverse agonist activity either among the existing medications or via a dedicated drug discovery program. Morphine-induced Straub tail response in mice is regarded as a model of transient spasticity that may be suitable for supporting such drug discovery efforts. Subcutaneous injection of morphine (10-60mg/kg) induced a dose-dependent Straub tail reaction in male Swiss mice with maximum response obtained 15-30min after the morphine administration. When given prior to morphine, 5-HT_2B/2C receptor inverse agonists cyproheptadine (1-10mg/kg, i.p.) and SB206553 (0.3-3mg/kg, i.p.) diminished Straub tail reaction dose-dependently without affecting spontaneous locomotor activity. In contrast, 5-HT_2B/2C receptor antagonist methysergide (1-5.6mg/kg, i.p.) and 5-HT_2C receptor antagonist SB242084 (1-5.6mg/kg, i.p.) as well as 5-HT_2A receptor inverse agonist pimavanserin (1-10mg/kg, i.p.) had no appreciable effects on Straub tail response. Taken together, the findings indicate that constitutive activity of 5-HT_2B/2C receptor may be involved in the mechanisms of morphine-induced spasticity. Thus, morphine-induced Straub tail response may be evaluated further as a candidate higher throughput test to identify 5-HT_2C receptor inverse agonists with anti-spasticity effects in vivo.

Animal models of the serotonin syndrome: a systematic review

The serotonin syndrome (SS) is a potentially life-threatening disorder in humans which is induced by ingestion of an overdose or by combination of two or more serotonin (5-HT)-enhancing drugs. In animals, acute administration of direct and indirect 5-HT agonists also leads to a set of behavioral and autonomic responses. In the current review, we provide an overview of the existing versions of the animal model of the SS. With a focus on studies in rats and mice, we analyze the frequency of behavioral and autonomic responses following administration of 5-HT-enhancing drugs and direct 5-HT agonists administered alone or in combination, and we briefly discuss the receptor mediation of these responses. Considering species differences, we identify a distinct set of behavioral and autonomic responses that are consistently observed following administration of direct and indirect 5-HT agonists. Finally, we discuss the importance of a standardized assessment of SS responses in rodents and the utility of animal models of the SS in translational studies, and provide suggestions for future research.

Design, synthesis, and biological evaluation of estrone-derived hedgehog signaling inhibitors

The design, synthesis and biological evaluation of new analogs of the naturally occurring compound cyclopamine, a Hedgehog signaling inhibitor, are described. Stucture-activity relationship studies lead to an evolving model for the pharmacophore of this medically promising compound class of anti-cancer chemotherapeutic agents.

Synthesis and structure revision of nakiterpiosin

This manuscript describes a convergent synthesis and the revision of the relative stereochemistry of nakiterpiosin, a marine C-nor-D-homosteroid. Our synthesis features a late-stage carbonylative Stille cross-coupling reaction and a photo-Nazarov cyclization reaction that deliver the complete nakiterpiosin skeleton efficiently.

Effects of serotoninergic drugs on tremor induced by physostigmine in rats

We investigated the effects of various serotoninergic drugs and serotonin (5-HT) depletion on physostigmine-induced visible tremor in rats. Physostigmine (0.25-1.5 mg/kg) caused dose-dependent tremor, initiated at 3-5 min (latency decreases as dose increases) and lasted for 30-35 min. Serotonin agonists, 8-hydroxy-2-(di-n-propylamino) tetralin (2.5 mg/kg) and buspirone (5 mg/kg) augmented the tremor response caused by physostigmine. The 5-HT(1)/5-HT(2) receptor antagonist, metergoline (1 mg/kg), and 5-HT(2) blocker, cyproheptadine (10 mg/kg) significantly decreased the duration (40%) as well as intensity (45-50%) of physostigmine-tremor. The 5-HT(2a)/5-HT(2c) antagonist ritanserin (5 mg/kg) significantly reduced the duration (60%) without affecting the intensity of the tremor. In 5-HT depleted rats (p-chlorophenylalanine; 300 mg/kg, for 3 days), physostigmine failed to produce tremor. Interestingly, in these animals, administration of a non-specific 5-HT agonist, 5-methoxy-N,N-dimethyl tryptamine, caused high intensity tremor. These results suggest that presence of 5-HT at the pre-synaptic terminals is needed for the tremor response by physostigmine and the response is greatly mediated via post-synaptic 5-HT receptors. The overall data indicated a direct involvement of central 5-HT system in the cholinergic tremor induced by physostigmine.