Synthesis and activity of 2-methyl-3-aminopropiophenones as centrally acting muscle relaxants

Combined Simulation and Mutation Studies to Elucidate Selectivity of Unsubstituted Amphetamine-like Cathinones at the Dopamine Transporter

The dopamine and serotonin transporter proteins (DAT, SERT) play a vital role in behavior and mental illness. Although their substrate transport has been studied extensively, the molecular basis of their selectivity is not completely understood yet. In this study, we exploit molecular dynamics simulations combined with mutagenesis studies to shed light on the driving factors for DAT-over-SERT selectivity of a set of cathinones. Results indicate that these compounds can adopt two binding modes of which one is more favorable. In addition, free energy calculations indicated the substrate binding site (S1) as the primary recognition site for these ligands. By simulating DAT with SERT-like mutations, we hypothesize unsubstituted cathinones to bind more favorably to DAT, due to a Val152 offering more space, as compared to the bulkier Ile172 in SERT. This was supported by uptake inhibition measurements, which showed an increase in activity in SERT-I172V.

Pharmacological examination of trifluoromethyl ring-substituted methcathinone analogs

Cathinones are a class of drugs used to treat various medical conditions including depression, obesity, substance abuse, and muscle spasms. Some "designer" cathinones, such as methcathinone, mephedrone, and methylone, are used nonclinically for their stimulant or entactogenic properties. Given the recent rise in nonmedical use of designer cathinones, we aimed to improve understanding of cathinone pharmacology by investigating analogs of methcathinone with a CF(3) substituent at the 2-, 3-, or 4-position of the phenyl ring (TFMAPs). We compared the TFMAPs with methcathinone for effects on monoamine uptake transporter function in vitro and in vivo, and for effects on locomotor activity in rats. At the serotonin transporter (SERT), 3-TFMAP and 4-TFMAP were 10-fold more potent than methcathinone as uptake inhibitors and as releasing agents, but 2-TFMAP was both a weak uptake inhibitor and releaser. At the norepinephrine and dopamine transporters (NET and DAT), all TFMAP isomers were less potent than methcathinone as uptake inhibitors and releasers. In vivo, 4-TFMAP released 5-HT, but not dopamine, in rat nucleus accumbens and did not affect locomotor activity, whereas methcathinone increased both 5-HT and dopamine and produced locomotor stimulation. These experiments reveal that TFMAPs are substrates for the monoamine transporters and that phenyl ring substitution at the 3- or 4-position increases potency at SERT but decreases potency at NET and DAT, resulting in selectivity for SERT. The TFMAPs might have a therapeutic value for a variety of medical and psychiatric conditions and may have lower abuse liability compared to methcathinone due to their decreased DAT activity.

Stereochemical study of tolperisone, a muscle relaxant agent, by circular dichroism and ultraviolet spectroscopy

The stereochemistry of tolperisone, a chiral aryl-alkyl basic ketone was investigated by means of circular dichroism (CD) and ultraviolet (UV) spectroscopy. The unusually high optical activity of tolperisone hydrochloride in the n-->pi* region is interpreted by the presence of a chiral conformer in solution. For stereochemical reasons, the C = O group and the aromatic moiety lack coplanarity by forming an inherently dissymetric chromophore, of M helicity. Similar helicity prevails in the crystal phase, according to the solid-state CD spectrum of (-)-tolperisone HCl salt. The chirality rule proposed by Snatzke for nonplanar benzoyl chromophores predicts the absolute configuration of (-)-tolperisone hydrochloride to be R, in agreement with other alpha-methyl-beta-amino-ketones.

Effects of a new centrally acting muscle relaxant, NK433 (lanperisone hydrochloride) on spinal reflexes

(-)-(R)-2-methyl-3-(1-pyrrolidinyl)-4'-trifluoromethylpropiophenone++ + monohydrochloride, lanperisone hydrochloride (NK433) administered intravenously or orally depressed the mono- and polysynaptic reflex potential, dorsal root reflex potential, flexor reflex mediated by group II afferent fibers, patellar and flexor reflexes. These effects were reduced by spinal transection. NK433 inhibited the facilitation of the flexor reflex mediated by group II afferent fibers that was induced by intrathecal administration of noradrenaline-HCl. (+)-(1R,2R)-2-methyl-3-(1-pyrrolidinyl)-1-(4-trifluoromethylphenyl)-1-pr opanol (LPS-9)-HCl, a metabolite of NK433, also inhibited the spinal reflexes. Given orally, NK433 had effects more than three times stronger and tending to be longer-lasting than those of eperisone-HCl. These results suggest that NK433 exerts a non-selective inhibition on spinal reflexes and that inhibition of the descending noradrenergic tonic facilitation within the spinal cord is involved in the mechanism of spinal reflex depression by NK433. LPS-9 could contribute to the potent activity of NK433 after oral administration.

Effects of NK433, a new centrally acting muscle relaxant, on masticatory muscle reflexes in rats

The effects of (-)-(R)-2-methyl-3-(1-pyrrolidinyl)-4'- trifluoromethylpropiophenone monohydrochloride (NK433), a novel centrally acting muscle relaxant, on masticatory muscle reflexes were investigated in rats. NK433 inhibited the monosynaptic tonic vibration reflex of the masseter muscle and the polysynaptic tonic periodontal masseteric reflex. These reflexes are increased by gamma-motor activity. NK433 had a weak inhibitory effect on the polysynaptic jaw opening reflex evoked by electrical stimulation of the tooth pulp, which is little related with gamma-motor activity. Eperisone-HCl depressed the three types of masticatory muscle reflexes. When intravenously administered, eperisone-HCl was equipotent to NK433, but the effect of eperisone-HCl was shorter-lasting than that of NK433. The effect of intragastrically administered NK433 on the periodontal masseteric reflex was about three times stronger than that of eperisone-HCl. These results suggest that NK433 inhibits masticatory muscle reflexes controlled by the gamma-motor system and thus may ameliorate the temporomandibular joint syndrome in man.