Germacrone and sesquiterpene-enriched extracts from Curcuma aeruginosa Roxb. increase skin penetration of minoxidil, a hair growth promoter

Minoxidil is approved for topical treatment of androgenic alopecia but hampered by poor cutaneous absorption. Recently, the randomized control trial showed that hair loss treatment of minoxidil was improved by co-application of the anti-androgen, Curcuma aeruginosa Roxb. extract. Here, we aimed to show that the apparent synergism arises from improved cutaneous penetration of minoxidil by bioactive compound, germacrone or C. aeruginosa (as an n-hexane extract, or essential oil). The partition coefficient of germacrone was determined by HPLC. Skin penetration was measured ex vivo on Franz diffusion cells using full thickness human foreskin as membranes. The receiver solution was sampled hourly for 8 h after which the skin was removed, the stratum corneum separated, and minoxidil assayed in this and in the remaining viable skin layer by HPLC. Skin penetration of minoxidil with 0.2 and 2% extract was increased ~ 4-fold (accumulated amount in receiver + skin viable layer after 8 h). Furthermore, germacrone enhanced minoxidil flux by ~ 10-fold and C. aeruginosa essential oil by ~ 20-fold. This work suggests three clinical consequences: (i) minoxidil efficacy is promoted, (ii) lower doses of minoxidil suffice, and (iii) C. aeruginosa extract/essential oil or germacrone can supplement treatment outcomes by acting as anti-androgen, thereby introducing a more effective topical treatment strategy for androgenic alopecia.

Phosphodiesterase 5 Inhibitors from Derris scandens

Phosphodiesterase 5 inhibitors have been used as a first-line medicine for the treatment of erectile dysfunction. In the search for new phosphodiesterase 5 inhibitors from natural sources, we found that the 95% ethanol extract of Derris scandens stem showed phosphodiesterase 5 inhibitory activity with an IC₅₀ value of about 7 µg/mL. Seven isoflavones and a coumarin constituent isolated from this plant were investigated for phosphodiesterase 5 inhibitory activity. The results showed that osajin (8: ), 4',5,7-trihydroxybiprenylisoflavone (4: ), and derrisisoflavone A (2: ) had the ability to inhibit phosphodiesterase 5 with IC₅₀ values of 4, 8, and 9 µM, respectively. These compounds exhibited selectivity on phosphodiesterase 5 over phosphodiesterase 1, however, the selectivity on phosphodiesterase 5 over phosphodiesterase 6 was low. In order to quantitatively determine these bioactive constituents in D. scandens extract, LC-QTOF-MS method has been developed and validated. The limit of quantitation values in the range of 0.1 - 5 µg/mL were obtained. The assay showed satisfactory precision and accuracy. The results from our method showed that the 95% ethanol extract of D. scandens stem was comprised of all eight compounds, with derrisisoflavone A (2: ) and lupalbigenin (3: ) presenting as the major constituents.

Curcuma aeruginosa Roxb. essential oil slows hair-growth and lightens skin in axillae; a randomised, double blinded trial

BACKGROUND

Androgenic hair-growth contributes to secondary gender characteristics but can be troublesome in women. Inhibiting axillary hair-growth via 5-α-reductases using the Thai medicinal plant, Curcuma aeruginosa Roxb. is an attractive treatment strategy.

HYPOTHESIS/PURPOSE

C. aeruginosa essential oil (CA-oil) formulated as a lotion is an efficacious and safe inhibitor of axillary hair growth.

STUDY DESIGN

This trial was a single center, randomized, double-blind, placebo controlled 10 weeks, intervention in 60 women (18-23 years) and 2 weeks washout with axillary hair length was the primary end-point.

METHODS

Bioactive-enriched essential oil of C. aeruginosa was formulated with a base lotion. All participants were pre-challenged with lotions by 4-h patch irritation tests to exclude skin reactions. Participants were randomly allocated to use either 1 or 5%w/w CA-oil lotion on one axilla and base-lotion (placebo) to the other for 10 weeks followed by placebo in both axillae for 2 weeks. Every week, the axillae were photographed to measure hair lengths, shaved, and roll-on applicators containing appropriate lotion replaced. Also, skin melanin by spectrophotometry and hair density were measured.

RESULTS

From weeks 5-11 of trial, 1 and 5%w/w CA-oil retarded growth by 13 ± 1.5% and 16 ± 0.9% respectively, while placebo was ineffective. CA-oil had no influence on hair density. Both concentrations of CA-oil rapidly and equally effectively brightened skin within 3 weeks which persisted 2 weeks after treatment ceased while placebo darkened the skin. Adherence appeared good as judged by consistency of lotion consumption and between axillae. Participants were satisfied with the treatment and reported reduced hairiness, freedom from any discomforts, but product odour attracted some negative comment. No adverse reactions ascribed to CA-oil were detected or reported.

CONCLUSION

This study points to a safe and efficacious dual action on retarding hair-growth and skin lightening by CA-oil.

Phenanthrenes from Eulophia macrobulbon as Novel Phosphodiesterase-5 Inhibitors

Phosphodiesterase 5 (PDE5) inhibitors can be used for the treatment of erectile dysfunction and pulmonary hypertension. In order to search for new leads of PDE5 inhibitors, we investigated the chemical constituents of the tubers of Eulophia macrobulbon (E.C. Parish & Rchb. f) Hook. f A new phenanthrene, 9,10-dihydro-4-(4′-hydroxybenzyl)-2,5-dimethoxyphenanthrene-1,7-diol (1) and three known phenanthrenes i.e., 1-(4′-hydroxybenzyl)-4,8-dimethoxyphenanthrene-2,7-diol (2), (9,10-dihydro-2,5-dimethoxyphenanthrene-1,7-diol (3) and 1,5,7-trimethoxyphenanthrene-2,6-diol) (4) were isolated. Among these, 2 was the most potent PDE5 inhibitor (IC50 =1.67±0.54 μM) evaluated by the [3H]cGMP radioassay method, whereas 1 showed mild activity (IC50 = 62.3±3.3 μM). Their inhibitory selectivities against PDE5 over PDE6 were also studied. This study suggests phenanthrenes as a new class of PDE5 inhibitors.

Phenanthrenes from Eulophia macrobulbon as Novel Phosphodiesterase-5 Inhibitors

Phosphodiesterase 5 (PDE5) inhibitors can be used for the treatment of erectile dysfunction and pulmonary hypertension. In order to search for new leads of PDE5 inhibitors, we investigated the chemical constituents of the tubers of Eulophia macrobulbon (E.C. Parish & Rchb. f.) Hook. f. A new phenanthrene, 9,10-dihydro-4-(4'-hydroxybenzyl)-2,5-dimethoxyphenanthrene-1,7-dio (1) and three known phenanthrenes i.e., 1-(4'-hydroxybenzyl)-4,8- dimethoxyphenanthrene-2,7-diol (2), (9,10-dihydro-2,5-dimethoxyphenanthrene-1,7-diol (3) and 1,5,7-trimethoxyphenanthrene-2,6-diol). (4) were isolated Among these, 2 was the most potent PDE5 inhibitor (IC₅₀ =1.67±0.54 μM) evaluated by the [3H]cGMP radioassay method, whereas 1 showed mild activity (IC₅₀ = 62.3±3.3 μM). Their inhibitory selectivities against PDE5 over PDE6 were also studied. This study suggests phenanthrenes as a new class of PDE5 inhibitors.

A new label-free screen for steroid 5α-reductase inhibitors using LC-MS

Steroid 5α-reductase (S5αR) plays an important role in metabolizing testosterone into active androgen dihydrotestosterone (DHT) which is involved in many androgen dependent disorders, such as androgenic alopecia, benign prostatic hyperplasia and acne. The method for screening for S5αR inhibition is key in finding new antagonists. In this study, the label-free S5αR inhibitory assay using LC-MS was developed. S5αR type 1 enzyme was obtained from LNCaP prostate cancer cells. The enzymatic assay was optimised for enzyme-substrate (testosterone) concentration, NADPH-cofactor concentration, solvent tolerance, enzyme activity stability and incubation time. The developed assay was validated by measuring the signal to background ratio (S/B), the signal to noise ratio (S/N), the signal window (SW) and the zeta factor Z' in accordance with published bioassay guidelines. The enzymatic reaction was performed in 96-well plates and DHT formation was determined by LC-MS. S/B, S/N, SW and Z' factor were well above acceptable criteria and the reproducibility was good using Z' factor other 3days and further validated by dutasteride and finasteride inhibition. The method was successfully applied to quantify S5αR inhibitory activity of some Thai herbal extracts. Two plant extracts, Impatiens balsamina L. and Curcuma longa L. showed IC₅₀ at 5.4±0.2 and 9.0±1.2μgmL^-1 and are therefore promising sources of new S5αR inhibitors. The assay has high selectability and reproducibility and suited to medium throughput screening required by phytochemistry.

Germacrene Analogs are Anti-androgenic on Androgen-dependent Cells

Anti-androgenic drugs are treatments for androgen-related disorders such as benign prostatic hyperplasia, acne, hirsutism, and androgenic alopecia. Germacrone (1), a sesquiterpene isolated from hexane extracts of Curcuma aeruginosa Roxb. rhizome, is an androgen inhibitor of steroid 5-alpha reductase in-vitro. Here, we used the similarity of germacrone's α,ß-unsaturated carbonyl to testosterone's α,ß-unsaturated carbonyl to find germacrene analogs obtained from this plant and by semi-synthesis that might be more potent steroid 5-alpha reductase inhibitors. 8-Hydroxy germacrene B (4) was ~13-fold more potent than its parent, 1 and the most potent (IC50, 0.15±0.022 mM) among 9 compounds tested. The conformation of its cyclodecadiene ring and the α,ß-unsaturated ketone/hydroxy in the germacrene molecule might be crucial role for its anti-androgen activity. Moreover, 1 and 4 showed mild cytotoxic effect on prostate cancer cells. Neither compound was cytotoxic towards human dermal papilla cells at 100 μg/mL. We show that this SAR strategy created promising anti-androgenics for androgen dependent disorders and may create further analogues with further improvements in selectivity and clinical efficacy.

Germacrene Analogs are Anti-androgenic on Androgen-dependent Cells

Anti-androgenic drugs are treatments for androgen-related disorders such as benign prostatic hyperplasia, acne, hirsutism, and androgenic alopecia. Germacrone (1), a sesquiterpene isolated from hexane extracts of Curcuma aeruginosa Roxb. rhizome, is an androgen inhibitor of steroid 5-alpha reductase in- vitro. Here, we used the similarity of germacrone's ,t,B-unsaturated carbonyl to testosterone's α,β-unsaturated carbonyl to find germacrene analogs obtained from this plant and by semi-synthesis that might be more potent steroid 5-alpha reductase inhibitors. 8-Hydroxy germacrene B (4) was -13-fold more potent than its parent, I and the most potent (ICso, 0.15 ± 0.022 mM) among 9 compounds tested. The conformation of its cyclodecadiene ring and the α,β-unsaturated ketone/hydroxy in the germacrene molecule might be crucial role for its anti-androgen activity. Moreover, I and 4 showed mild cytotoxic effect on prostate cancer cells. Neither compound was cytotoxic towards human dermal papilla cells at 100 μg/mL. We show that this SAR strategy created promising anti-androgenics for androgen dependent disorders and may create further analogues with further improvements in selectivity and clinical efficacy.

Curcumin analogues inhibit phosphodiesterase-5 and dilate rat pulmonary arteries

Objectives

Phosphodiesterase (PDE)-5 inhibitors are useful as vasodilators for the treatment of pulmonary arterial hypertension. We aimed to study curcumin analogues for PDE5 inhibitory activity and vasorelaxation of rat pulmonary arteries.

Methods

Three natural curcuminoids (1–3) and six synthetic analogues (4–9) were tested for PDE5 and PDE6 inhibitory activities using enzymatic radioassay. Their vasorelaxation was measured using freshly isolated segments of rat pulmonary artery and aorta.

Key findings

Curcuminoids (1–3) mildly inhibited PDE5 (half maximal inhibitory concentration (IC50) = 18 µm): the metamethoxyl of curcumin was important for PDE5 inhibition. But hydroxyl rearrangements, removing both methoxyls and one ketomethylene, yielded the potent 7 and 9 (IC50 = 4 µm) (compared with sildenafil, IC50 = 0.03 µm). Only 1, 3 and 4 were PDE5 selective over PDE6. Triazole-carboxylic addition provided water-solubility while preserving potency. All analogues possessed concentration-dependent vasorelaxant activity on pulmonary arteries (40% of maximal effective concentration (EC40) = 29–90 µm, maximum response = 60–90% at 300 µm), while compounds (1–8) were weakly acting in aorta (maximum response <40%). Only demethoxycurcumin (2) and analogues 5, 8, 9 had endothelium-dependent actions. Sildenafil was highly potent (EC40 = 0.04 µm) and highly endothelium dependent in pulmonary artery but weak on intact aorta (EC40 = 1.8 µm). Activity profiles suggest actions through additional cell pathways for promoting vasorelaxation.

Conclusions

Curcumin analogues are potential leads for developing efficacious and selective PDE5 inhibitors and other pathologies of pulmonary hypertension.

Stability studies of antiandrogenic compounds in Curcuma aeruginosa Roxb. extract

OBJECTIVES

Curcuma aeruginosa Roxb. extract is a 5α-reductase antagonist that can be used to treat hair loss. We aimed to study the stability of antiandrogenic constituents, germacrone and other sesquiterpene components in the extract.

METHODS

Germacrone and the extract were analyzed as solid forms or solublized with polyethylene glycol-40 (PEG-40) or methanol using high-performance liquid chromatography and gas chromatography with flame ionization detector. The effects of pH, temperature and light on their stability were studied.

KEY FINDINGS

Degradation of antiandrogenic compounds in C. aeruginosa was highly sensitive to temperature especially pure anhydrous germacrone, which was completely lost within 3 days at 45°C. Curiously, degradation was slower than as a dried extract. Paradoxically, when solubilized with PEG-40, it was largely intact even after 90 days at 45°C. The MS spectrum of a major degradation product suggested that it was elemenone probably produced by Cope rearrangement. Two other putative degradation products were germacrone-1,10-epoxide and germacrone-4,5-epoxide suggesting that oxidation of double bonds was an important mechanism. Germacrone stability was unaffected by pH (2.0-9.0) but only as dried extract it was slightly degraded by light.

CONCLUSION

Antiandrogenic constituents of C. aeruginosa were instable at high temperature and in solid form. Thus, the extract would be optimately stored as a solution or otherwise as solid form at low temperature.

Conformational analysis of an anti-androgenic, (E,E)-8-hydroxygermacrene B, using NOESY and dynamic NMR spectroscopy

(E,E)-8-Hydroxygermacrene B was prepared by ketone reduction of germacrone, a naturally occurring compound from Curcuma aeruginosa Roxb. with NaBH4 at low temperature (4 °C). This compound showed remarkable in vitro anti-androgenic activity (IC50 0.15±0.022 mM) applicable to male baldness treatments. NMR analysis at -50 °C indicated that there were four conformational isomers of (E,E)-8-hydroxygermacrene B in a ratio of 48:40:8:4. The major conformers were assigned by (1)H NMR and 2D-NOESY NMR spectroscopy as having methyl groups at C-10 and C-4 in up-down (UD) orientations (48% predominance) and UU (40%). (1)H NMR spectra implied another two minor conformers with these methyls having DU (8%) and DD (4%) orientations.

Anti-androgenic effect of sesquiterpenes isolated from the rhizomes of Curcuma aeruginosa Roxb

Six sesquiterpenes: germacrone (1), zederone (2), dehydrocurdione (3), curcumenol (4), zedoarondiol (5) and isocurcumenol (6) were isolated from rhizomes of Curcuma aeruginosa Roxb. (Zingiberaceae). They inhibited 5α-reductase which converts testosterone to dihydrotestosterone (DHT). Germacrone (1) was the most potent (IC(50)=0.42±0.05 mg/mL). Compound 1 was anti-androgenic in LNCaP cells when proliferation was testosterone-induced. The growth of flank gland of male Syrian hamsters is dependent on circulating androgen and when maintained with testosterone, 1 (3, 30, 100μg) inhibited growth but was ineffective against DHT. The similar activity profile was observed on the 5α-reductase inhibitor, finasteride (100 μg) treatment group. The androgen receptor binding assay showed that 1 did not bind to the androgen receptor. In conclusion, 1 showed anti-androgenic effect on in vitro and in vivo assays. One of the possible mechanisms was inhibition 5α-reductase activity. Thus, 1 is a potential lead compound for treatment of androgen-dependent disorders.

Piperine inhibits cytokine production by human peripheral blood mononuclear cells

Piperine, an amide isolated from Piper species (Piperaceae), has been reported to exhibit central nervous system depression, anti-pyretic and anti-inflammatory activity. Immunomodulatory and anti-tumor activity of piperine has been demonstrated in mouse carcinomas. However, there is little information available concerning the effect of piperine on humans. We evaluated the immunopharmacological activity of this compound in human immune cells. Human peripheral blood mononuclear cells (PBMCs) were exposed to piperine, and cell proliferation was determined by the MTS assay. Piperine significantly inhibited phytohemagglutinin-stimulated human PBMC proliferation after exposure for 72 h. This compound inhibited PBMC activity, with an IC(50) of 100.73 ± 11.16 μg/mL. Production of interleukin-2 (IL-2) and interferon-γ (IFN-γ) was measured using an ELISA assay and RT-PCR. Piperine inhibited IL-2 and IFN-γ production in the PBMCs. RT-PCR data indicated that IL-2 and IFN-γ mRNA expression in PBMCs is suppressed by piperine. This compound significantly inhibited the production of these two cytokines by activated PBMCs in a dose-dependent manner. In conclusion, piperine appears to have potential as an immunomodulatory agent for immune system suppression.

Acetylcholinesterase inhibitors from Stephania venosa tuber

Acetylcholinesterase (AChE) inhibitors have lately gained interest as potential drugs in the treatment of Alzheimer's disease. Three AChE inhibitors were isolated from tubers of a Thai medicinal plant, Stephania venosa (Bl) Spreng. They were identified as quaternary protoberberine alkaloids, stepharanine, cyclanoline and N-methyl stepholidine. They expressed inhibitory activity on AChE with IC50 values (concentration that caused 50% inhibition of activity) of 14.1K ± 0.81, 9.23 ± 3.47 and 31.30 ± 3.67 μM, respectively. The AChE inhibitory activity of these compounds was compared with those of the related compounds, palmatine, jatrorrhizine and berberine, as well as tertiary protoberberine alkaloids isolated from the same plant, stepholidine and corydalmine. The results suggest that the positive charge at the nitrogen of the tetrahydroisoquinoline portion, steric substitution at the nitrogen, planarity of the molecule or substitutions at C-2, −3, −9, and −10 affect the AChE inhibitory activity of protoberberine alkaloids.

Effect of 8-hydroxy-2-(N,N-di-n-propylamino)tetralin and MDMA on the discriminative stimulus effects of the classical hallucinogen DOM in rats

Co-administration of the 5-HT1A serotonin receptor agonist (+/-)8-hydroxy-2-(N,N-di-n-propylamino)tetralin [(+/-)8-OH DPAT] enhances the discriminative stimulus effects of the classical hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) in rats. In the present investigation, using Sprague-Dawley rats trained to discriminate DOM (1.0 mg/kg) from saline vehicle under a VI-15 s schedule of reinforcement, it was shown that the stimulus-enhancing actions of 8-OH DPAT are related more to its R(+)-isomer than to its S(-)-enantiomer, and that the (+/-)- and R(+)8-OH DPAT-induced effects are antagonized by the 5-HT1A receptor antagonist NAN-190. (+/-)8-OH DPAT and its isomers substitute in rats trained to discriminate the designer drug N-methyl-1-(3,4-methylenedioxyphenyl)-2-aminopropane (MDMA; methylenedioxymethamphetamine) from vehicle indicating some similarity of effect. On this basis, it was hypothesized that MDMA might be capable of enhancing the DOM stimulus. Co-administration of MDMA with low (i.e., 0.1 and 0.3 mg/kg) doses of DOM resulted in greater DOM-appropriate responding than engendered by administration of DOM alone. As such, the present findings are the first to demonstrate an MDMA-induced enhancing effect on the discriminative stimulus actions of a classical hallucinogen. The results also suggest that a 5-HT1A serotonin receptor mechanism might contribute to this phenomenon.

Isoquinoline derivatives as potential acetylcholinesterase inhibitors

Several bisbenzylisoquinoline alkaloid derivatives showed the inhibitory activity at acetylcholinesterase enzyme (AChE) in micromolar range. It is possible that monomeric moiety of bisbenzylisoquinoline alkaloid might be required for acetylcholinesterase enzyme inhibition. AChE inhibitory activity of related monomeric 1-benzylisoquinolines was examined by using Ellman colorimetric assay with galanthamine as a reference standard.

Pizotyline effectively attenuates the stimulus effects of N-methyl-3,4-methylenedioxyamphetamine (MDMA)

MDMA (N-methyl-3,4-methylenedioxyamphetamine) produces a discriminative stimulus (DS) effect in animals, but attempts to completely block this action with selective neurotransmitter antagonists have not been very successful. Biochemically, MDMA can increase synaptic levels of serotonin, dopamine, and norepinephrine that, conceivably, might interact with multiple populations or subpopulations of neurotransmitter receptors. The present study attempted to antagonize the DS effects of MDMA using the nonselective agents clozapine, cyproheptadine, and pizotyline. An extensive and comparative radioligand binding profile was also obtained for the latter two agents. The purported antagonists were administered in combination with the training dose of MDMA to groups of Sprague-Dawley rats trained to discriminate 1.5 mg/kg of MDMA from saline vehicle in a standard two-lever operant paradigm using a VI-15s schedule of reinforcement. Clozapine was without effect at the doses evaluated, and cyproheptadine only partially attenuated MDMA-appropriate responding. In contrast, pizotyline (AD50=2.5 mg/kg), in combination with the MDMA training dose, resulted in a dose related decrease in percent drug-appropriate responding to saline levels. In a separate group of animals trained to discriminate the structurally-related agent N-methyl-1-(4-methoxyphenyl)-2-aminopropane (PMMA) from vehicle, pretreatment with pizotyline also resulted in a substantial decrease in drug-appropriate responding. The results with cyproheptadine and pizotyline in the binding assays confirmed that these agents display high affinity for multiple subpopulations of serotonergic, dopaminergic, adrenergic, histaminergic, and cholinergic receptors. The overall results of the present investigation indicate that pizotyline, which is clinically available in some countries, might be of clinical utility in the treatment of MDMA overdose.

Beta-oxygenated analogues of the 5-HT2A serotonin receptor agonist 1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane

Activation of 5-HT(2A) serotonin receptors represents a novel approach to lowering intraocular pressure. Because 5-HT(2A) serotonin receptor agonists might also produce undesirable central effects should sufficient quantities enter the brain, attempts were made to identify 5-HT(2) serotonin receptor agonists with reduced propensity to penetrate the blood-brain barrier. 1-(4-Bromo-2,5-dimethoxyphenyl)-2-aminopropan-1-ol (6), an analogue of the 5-HT(2) serotonin receptor agonist 1-(4-bromo-2,5-dimethoxyphenyl)-2-aminopropane (DOB; 1a) bearing a benzylic hydroxyl group, was identified as a candidate structure. Of the four optical isomers of 6, the 1R,2R-isomer (6d; K(i) = 0.5 nM) was found to bind at 5-HT(2A) receptors with an affinity similar to that of R(-)DOB (K(i) = 0.2 nM). Like R(-)DOB, 6d behaved as a partial agonist (efficacy ca. 50%) in a 5-HT(2)-mediated calcium mobilization assay. However, in an in vivo test of central action (i.e., stimulus generalization with rats as subjects), 6d was >15 times less potent than R(-)DOB. O-Methylation of 6d (i.e., 7d; 5-HT(2A) K(i) = 0.3 nM) resulted in an agent that behaved as a full (93% efficacy) agonist. Intraocular administration of 300 microg of 6d and 7d to ocular hypertensive monkeys was shown to reduce intraocular pressure by 20-27%. Given the route of administration (i.e., topical), and concentrations necessary to reduce intraocular pressure, compounds such as 6d should demonstrate minimal central effects at potentially useful therapeutic doses and offer useful leads for further development.

Stimulus effects of three sulfur-containing psychoactive agents

Two agents gaining popularity on the illicit drug market are the phenylalkylamines 4-MTA and 2C-T-7 [or 1-(4-methylthiophenyl)-2-aminopropane and 2-(2,5-dimethoxy-4-n-propylthiophenyl)-1-aminoethane, respectively]. At this time, there exists a paucity of information on the behavioral actions of these sulfur-containing agents. The present investigation examined these agents, and the N-monomethyl analog of 4-MTA (i.e., 4-MTMA), in tests of stimulus generalization (substitution) using a two-lever drug discrimination task with groups of rats trained to discriminate either the hallucinogen DOM [1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane], the stimulant cocaine, or the empathogen MDMA from vehicle. 4-MTA and its N-monomethyl analog 4-MTMA (ED50 = 0.8 mg/kg in both cases) substituted only for the MDMA stimulus, whereas 2C-T-7 (ED50 = 0.8 mg/kg) substituted only for the DOM stimulus. Thus, at the doses examined, 4-MTA and 4-MTMA appear to be MDMA-like agents, and 2C-T-7 seems best classified as a DOM-like hallucinogen. These results provide additional data that extend the structure-activity relationships of phenylalkylamines and that are consistent with what little is currently known about the action of 4-MTA and 2C-T-7 in humans.

Comparison of the discriminative stimulus effects of 3,4-methylenedioxymethamphetamine (MDMA) and cocaine: asymmetric generalization

Evidence suggests that +/- 3,4-methylenedioxymethamphetamine (MDMA) and psychostimulants produce similar but non-identical stimulus effects in animals. To examine this hypothesis, groups of rats were trained to discriminate either MDMA (1.5 mg/kg) or cocaine (8 mg/kg) from saline vehicle using a two-lever operant procedure under a variable interval (VI) 15 s schedule of reinforcement. Once the animals were trained, tests of stimulus generalization were conducted with +/- MDMA, cocaine, S+ MDMA, and R- MDMA. As previously demonstrated, both S+ MDMA and R- MDMA (ED50 = 0.8 and 1.2 mg/kg, respectively) substituted for +/- MDMA. Stimulus generalization also occurred upon administration of cocaine (ED50 = 4.6 mg/kg) to the +/- MDMA-trained animals. In the cocaine-trained animals, however, stimulus generalization did not occur to +/- MDMA, S+ MDMA nor R- MDMA. Receptor binding profiles for MDMA and cocaine were compared in an effort to identify any novel and common receptor-based mechanism(s) to explain stimulus generalization of MDMA-trained animals to the effects of cocaine, but only their actions on neurotransmitter transporters seem applicable. Taken together, the results indicate that stimulus substitution between MDMA and cocaine is asymmetric and suggest that although similarities exist between the stimulus actions of MDMA and cocaine, differences might be explained by their differential effects on increasing synaptic concentrations of serotonin (5-HT), dopamine (DA), and/or norepinephrine (NE).

Binding of tetrahydrocarboline derivatives at human 5-HT5A receptors

On the basis of an earlier finding that 5-methyl-5H-1,2,3,4-tetrahydropyrido[4,3-b]indole (5-methyl-1,2,3,4-tetrahydro-gamma-carboline; 1) binds at murine 5-HT(5A) receptors, preliminary structure-affinity studies were conducted. The present investigation extends these structure-affinity studies using human 5-HT(5A) receptors and examined additional analogues of 1. It was found (a) that there is little interspecies difference for the affinities of these compounds, (b) that an intact 1,2,3,4-tetrahydro-gamma-carboline ring system seems optimal and an N(2)-(3-(substituted-phenoxy)propyl) moiety results in high affinity, (c) that structurally related 1,2,3,4-tetrahydro-beta-carbolines also bind at 5-HT(5A) receptors, and (d) that all examined derivatives also possess affinity for 5-HT(2A) receptors. Evidence is provided that 5-HT(5A) and 5-HT(2A) receptor affinities probably do not covary and that it might be possible, with continued investigation, to develop analogues with enhanced 5-HT(5A) selectivity.

gamma-Carbolines: binding at 5-HT5A serotonin receptors

Screening of various agents resulted in the identification of 5-methyl-1,2,3,4-tetrahydro-gamma-carboline (1; K(i)=5,300 nM) as a compound with modest affinity for mouse 5-HT(5A) receptors. Structure-affinity studies were conducted resulting in 5-methyl-2-[3-(4-fluorophenoxy)propyl]-1,2,3,4-tetrahydro-gamma-carboline (17; K(i)=13 nM). Although 17 also binds at 5-HT(2) receptors, it serves as a novel lead for the further development of 5-HT(5A) ligands.

Ketanserin and spiperone as templates for novel serotonin 5-HT(2A) antagonists

The structures of ketanserin (1) and spiperone (2) were examined in detail to determine the role of various substituent groups on 5-HT(2A) receptor affinity and selectivity. It was found that the presence of the quinazoline ring of ketanserin detracts from selectivity and that various ring-opened analogs displayed ketanserin-like affinity and up to 30-fold enhanced selectivity. The triazaspirodecanone portion of spiperone is a major determinant of its 5-HT affinity and selectivity. The conformational rigidity imposed by the ring, as well as the nature of the N(1)-substituent, are important factors in controlling binding at 5-HT(2A), 5-HT(2C), 5-HT(1A), and dopamine D2 receptors. Replacement of the N(1)-phenyl ring of spiperone with a methyl group (KML-010; 48) resulted in a compound that binds at 5-HT(2A) receptors with slightly lower affinity than spiperone, but that lacked affinity (Ki >10,000 nM) for 5-HT(2C) and 5-HT(1A) receptors and binds with 400-fold reduced affinity at D2 receptors.