Synthetic Placement of Active Sites in MFI Zeolites for Selective Toluene Methylation to para-Xylene

Brønsted acidic zeolites are ubiquitous catalysts in fuel and chemical production. Broadening the catalytic diversity of a given zeolite requires strategies to manipulate the acid site placement at framework positions within distinct microporous locations. Here, we combine experiment and theory to elucidate how intermolecular interactions between organic structure-directing agents (OSDAs) and framework Al centers influence the placement of H+ sites in distinct void environments of MFI zeolites and demonstrate the catalytic consequences of active site location on kinetically controlled (403 K) toluene methylation to xylene regioisomers. Kinetic measurements, interpreted using mechanism-derived rate expressions and transition state theory, alongside density functional theory (DFT) calculations show that larger intersection environments similarly stabilize all three xylene isomer transition states without altering well-established aromatic substitution patterns (ortho/para/meta ∼ 60%:30%:10%), while smaller channel environments preferentially destabilize transition states that form bulkier ortho- and meta-isomers, thereby resulting in high intrinsic para-xylene selectivity (∼80%). DFT calculations reveal that the flexibility of nonconventional OSDAs (e.g., 1,4-diazabicyclo[2.2.2]octane) to reorient within MFI intersections and their ability to hydrogen-bond to form protonated complexes favor the placement of Al in smaller channel environments compared to conventional quaternary OSDAs (e.g., tetra-n-propylammonium). These molecular-level insights establish a mechanistic link between OSDA structure, active site placement, and transition state stability in MFI zeolites and provide active site design strategies that are orthogonal to crystallite design approaches harnessing complex reaction-diffusion phenomena to enhance regioisomer selectivity in the industrial production of valuable polymer precursors.

Heat-induced maternal effects shape avian eggshell traits and embryo development and phenotype at high incubation temperatures

Phenotypic plasticity is an important avenue by which organisms may persist in the face of rapid environmental change. Environmental cues experienced by the mother can also influence the phenotype of offspring, a form of plasticity called maternal effects. Maternal effects can adaptively prepare offspring for the environmental conditions they will likely experience; however, their ability to buffer offspring against environmental stressors as embryos is understudied. Using captive zebra finches, we performed a maternal-offspring environmental match-mismatch experiment utilizing a 2 × 2 × 2 factorial design. Mothers were exposed to a mild heat conditioning (38°C) or control (22°C) treatment as juveniles, an acute high heat (42°C) or control (22°C) treatment as adults, then paired for breeding. The eggs produced by those females were incubated at a hyperthermic (38.5°C) or optimal temperature (37.2°C). We found that when mothers were exposed to a mild heat conditioning as juveniles, their embryos exhibited reduced water loss, longer development times, and produced hatchlings with heavier pectoralis muscles when incubated at high incubation temperatures, compared to embryos from control mothers. Mothers exposed to both the mild heat conditioning as juveniles and a high heat stressor as adults produced eggs with a higher density of shell pores and embryos with lower heart rates during development. However, there was a cost when there was a mismatch between maternal and embryo environment. Embryos from these conditioned and heat-stressed mothers had reduced survival at control incubation temperatures, indicating the importance of offspring environment when interpreting potential adaptive effects.

Periodic Cooling during Incubation Alters the Adrenocortical Response and Posthatch Growth in Zebra Finches

AbstractIn birds, incubation temperature is critically deterministic for a range of traits. When parents leave the nest to forage, developing embryos can be exposed to cooling events that represent thermal stress. To investigate the consequences of periodic cooling on offspring development and physiology, we exposed zebra finch embryos to cooling events throughout the incubation period. We then compared embryonic survival, egg mass change, incubation duration, posthatch growth, and adrenocortical response of these individuals with embryos reared at a constant optimal temperature of 37.4°C and embryos reared at a constant suboptimal temperature of 36.4°C, the mean incubation temperature of periodically cooled embryos. There were no differences in embryonic survival or egg mass change during incubation, but individuals exposed to periodic cooling had longer incubation periods than those from the 37.4°C treatment and shorter incubation periods than those from the 36.4°C treatment. Periodically cooled individuals showed slower posthatch growth in comparison with both constant-temperature treatments, but this did not impact adult body size. Treatment groups did not differ in their adrenocortical response, but embryos exposed to periodic cooling and a constant temperature of 37.4°C were able to habituate to repeated capture and restraint stress, while individuals exposed to the constant temperature of 36.4°C were not. These results point to the differential impacts of cooling events versus constant low temperatures during incubation on posthatch growth and physiology and may represent a way for parents to devote less energy toward incubation while still ensuring offspring success.

Rigid Arrangements of Ionic Charge in Zeolite Frameworks Conferred by Specific Aluminum Distributions Preferentially Stabilize Alkanol Dehydration Transition States

Zeolite reactivity depends on the solvating environments of their micropores and the proximity of their Brønsted acid sites. Turnover rates (per H⁺ ) for methanol and ethanol dehydration increase with the fraction of H⁺ sites sharing six-membered rings of chabazite (CHA) zeolites. Density functional theory (DFT) shows that activation barriers vary widely with the number and arrangement of Al (1-5 per 36 T-site unit cell), but cannot be described solely by Al-Al distance or density. Certain Al distributions yield rigid arrangements of anionic charge that stabilize cationic intermediates and transition states via H-bonding to decrease barriers. This is a key feature of acid catalysis in zeolite solvents, which lack the isotropy of liquid solvents. The sensitivity of polar transition states to specific arrangements of charge in their solvating environments and the ability to position such charges in zeolite lattices with increasing precision herald rich catalytic diversity among zeolites of varying Al arrangement.

No Effect of Lifelong Methylmercury Exposure on Oxidative Status in Zebra Finches (Taeniopygia guttata): A Demonstration of Methylmercury-Induced Selection?

Songbirds exposed to methylmercury (MeHg) often exhibit reduced reproductive success and cognitive abilities. To better understand whether oxidative stress plays a role, we dosed zebra finches (Taeniopygia guttata) with a contaminated (1.2 ppm MeHg-cysteine) or control diet for their entire lives, including during development in the egg. Levels of antioxidant enzymes [superoxide dismutase (SOD1 and SOD2)], oxidative damage (4-hydroxynonenal; 4-HNE), and antioxidant transcription factors [nuclear factor (erythroid-derived 2)-like 2; Nrf2] were measured in the liver and pectoralis muscle of adults. MeHg treatment did not affect levels of 4-HNE or liver SOD2 or Nrf2. Birds in the MeHg treatment differed significantly from controls in pectoralis SOD1 and Nrf2, and tended to differ in liver SOD1 and pectoralis SOD2; however, we detected no overall pattern of effect of MeHg on oxidative status in dosed finches. We suspect that this is a consequence of the differential survival of MeHg-tolerant birds.

Photonic materials, structures and devices for Reststrahlen optics

We present a review of existing and potential next-generation far-infrared (20-60 μm) optical materials and devices. The far-infrared is currently one of the few remaining frontiers on the optical spectrum, a space underdeveloped and lacking in many of the optical and optoelectronic materials and devices taken for granted in other, more technologically mature wavelength ranges. The challenges associated with developing optical materials, structures, and devices at these wavelengths are in part a result of the strong phonon absorption in the Reststrahlen bands of III-V semiconductors that collectively span the far-infrared. More than just an underexplored spectral band, the far-IR may also be of potential importance for a range of sensing applications in astrochemistry, biology, and industrial and geological processes. Additionally, with a suitable far-IR optical infrastructure, it is conceivable that even more applications could emerge. In this review, we will present recent progress on far-infrared materials and phenomena such as phononic surface modes, engineered composite materials, and optoelectronic devices that have the potential to serve as the next generation of components in a far-infrared optical tool-kit.

Dispersive photon blockade in a superconducting circuit

Mediated photon-photon interactions are realized in a superconducting coplanar waveguide cavity coupled to a superconducting charge qubit. These nonresonant interactions blockade the transmission of photons through the cavity. This so-called dispersive photon blockade is characterized by measuring the total transmitted power while varying the energy spectrum of the photons incident on the cavity. A staircase with four distinct steps is observed and can be understood in an analogy with electron transport and the Coulomb blockade in quantum dots. This work differs from previous efforts in that the cavity-qubit excitations retain a photonic nature rather than a hybridization of qubit and photon and provides the needed tolerance to disorder for future condensed matter experiments.

Tunable coupling in circuit quantum electrodynamics using a superconducting charge qubit with a V-shaped energy level diagram

We introduce a new type of superconducting charge qubit that has a V-shaped energy spectrum and uses quantum interference to provide independently tunable qubit energy and coherent coupling to a superconducting cavity. Dynamic access to the strong coupling regime is demonstrated by tuning the coupling strength from less than 200 kHz to greater than 40 MHz. This tunable coupling can be used to protect the qubit from cavity-induced relaxation and avoid unwanted qubit-qubit interactions in a multiqubit system.

Chronic pain in individuals with spinal cord injury: a survey and longitudinal study

STUDY DESIGN

Cross-sectional and longitudinal postal survey.

OBJECTIVES

To (1) compare the severity of pain in persons with spinal cord injury (SCI) to national norms, (2) examine the association between pain and measures of (a) psychological functioning, (b) community integration and (c) pain interference with daily activities, and (3) examine the change in the prevalence and intensity of pain over time.

SETTING

Community.

METHODS

A total of 147 adults with SCI were surveyed twice, 2-6 years apart. Main outcome measures included presence/absence of pain in general and at specific body sites, 0-10 numerical rating scale of average pain intensity, modified Brief Pain Inventory Pain Interference scale, SF-36 Bodily Pain scale, SF-36 Mental Health scale, Community Integration Questionnaire.

RESULTS

Pain was more severe, on average, in this sample of patients with SCI than it is in normative samples. The presence of pain was associated with trends towards poorer psychological functioning and social integration, and the intensity of pain was associated with interference with a number of important basic activities of daily living. Little systematic change was found in pain over a 2-6-year-period, although there was evidence that the prevalence of shoulder pain increases over time.

CONCLUSION

The current findings underscore the serious nature of pain in persons with SCI and provide additional support for the need to identify effective treatments for SCI-related pain.

The effect of acoustic diffraction and acoustic attenuation on the dynamic range of acoustooptic Bragg cells

A three-dimensional model for the propagation of finite acoustic waves in nonlinear media is developed. This model implicitly includes the effects of acoustic attenuation and divergence due to diffraction. The generation of intermodulation products in the case of a two-tone input signal is numerically analyzed. It is found that acoustic diffraction can have a significant effect on the dynamic range of a Bragg cell if the acoustic field extends well into the Fraunhofer region. Inclusion of the effect of diffraction in the model predicts a dynamic range that can be considerably larger than the value obtained by using the infinite plane wave assumption. It is shown that acoustic attenuation significantly reduces the level of the acoustic intermodulation products relative to the level of the fundamental modes. This also increases the dynamic range. The influence of these effects on design considerations for Bragg cells is discussed.

Formulation for the design of birefringent phased-array Bragg cells in uniaxial crystals

Tangential phase matching is generally used as an enhancement technique in the design of wideband acousto-optic deflectors operating in birefringent media. We present an exact formulation that describes the behavior of birefringent phased-array Bragg cells in uniaxial crystals. It is demonstrated that wideband deflection around a desired center frequency can be obtained while one has freedom of choice regarding the acoustic mode and interaction plane. Furthermore it is shown that some major disadvantages of the optically rotated and acoustically rotated tangential phase-matching configurations can be eliminated.

[125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for the 5-HT2 receptor in rat frontal cortex

Recent studies of 5-HT2 receptor binding have involved the use of radiolabeled agonists. This report describes the use of [125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for low-density 5-HT2 agonist binding sites. A nonhydrolyzable analog of GTP, GppNHp, was found to inhibit the high affinity binding of [125I]-2C-I. 5-HT and several 5-HT2 agonists and antagonists displayed high affinity for this site. In addition, a significant decrease in the Bmax value, but not the KD for [125I]-2C-I was observed at 37 degrees C as compared to that observed at 24 degrees C. Several structure-activity relationships were investigated for displacement of [125I]-2C-I, and the results are consistent with the importance of this receptor in the mechanism of action of hallucinogens. This study demonstrates the utility of [125I]-2C-I as a novel radioligand and provides further data that the 5-HT2 receptor is significantly linked to hallucinogenic activity for several compounds.

Studies of dioxole ring substituted 3,4-methylenedioxyamphetamine (MDA) analogues

The 3,4-ethylidenedioxy and 3,4-isopropylidenedioxy analogues, EDA and IDA, respectively, of 3, 4-methylenedioxyamphetamine (MDA) were compared to MDA in drug-stimulated [3H]-serotonin overflow from prelabelled rat hippocampal slices, [3H]-dopamine overflow from prelabelled rat caudate slices, in their ability to displace the 5-HT2 agonist R-[125I]-DOI from rat brain cortical binding sites. They were also compared in the two-lever drug discrimination assay in rats, utilizing d-LSD tartrate (0.08 mg/kg) or MDMA.HCl (1.75 mg/kg) as the training stimulus. MDA and EDA were nearly equipotent in inducing release of both [3H]-monoamine transmitters, while IDA was considerably less potent. Pretreatment of hippocampal slices with the 5-HT-uptake inhibitor fluoxetine (3.2 microM) blocked the [3H]-5-HT overflow induced by MDA. In the drug discrimination experiments, complete substitution occurred with all three drugs in both LSD- and MDMA-trained rats. The ED50 values indicated that MDA had about twice the potency of EDA, and five times the potency of IDA in MDMA-trained rats. In the LSD-trained animals, MDA was about three times more potent than EDA and about seven times more potent than IDA. The KI values for displacement of R-[125I]-DOI generally parallel the results of the LSD transfer tests.

Conformational analysis and molecular modeling of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines as D1 dopamine receptor ligands

Conformational studies on a series of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines that possess an identical substituent pattern to the prototypical D1 dopamine receptor antagonist SCH23390 [(R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5- tetrahydro-1H-3-benzazepine (1)] were performed with use of molecular mechanics calculations [MM2(85), with newly developed aromatic halide bending and torsional parameters that are now incorporated into MM2(87)], single-crystal X-ray analysis, and high-field NMR spectroscopy. The synthesis and biological testing of compounds 2-7 has been previously reported. The test compounds were compared both quantitatively and graphically to compound 1. Calculations on both the free-base and protonated forms of each compound were carried out. To insure that conformation space was adequately sampled, the test compounds were energy minimized from different starting geometries; ring inversion of the heterocycle was employed, as were dihedral driver calculations on the phenyl or benzyl rings. For N-methyl-6-chloro-7-hydroxy-1-phenyl-1,2,3,4-tetrahydroisoquinoline (2), it was determined that the torsion angle tau(C8a-C1-C12-C17) had energy minima at approximately 60 degrees and 240 degrees. This finding was corroborated by NMR studies that indicated a dramatic upfield chemical shift of ArH8 after ring cyclization. The nitrogen lone pair or hydrogen vector was approximately orthogonal to the plane of the substituted aromatic ring in the tetrahydroisoquinolines; this explained the upfield chemical shift of the vicinal chiral proton (H1). In all instances, the 6-membered heterocyclic ring in the energy-minimized structures preferred the half-chair conformation with the phenyl rings pseudo-equatorial. Distance comparisons of the proposed pharmacophoric atoms (Cl, N, O, centroid of the phenyl or benzyl ring) showed that the phenyl or benzyl centroid to ammonium H distance, Cl to N distance, and distance of the nitrogen above or below the plane of the isoquinoline aromatic ring are the distances most highly correlated with biological activity (r = 0.82, 0.75, 0.81, respectively). Resolution and single-crystal X-ray analysis of compound 2 showed the most active enantiomer to possess the S absolute configuration, in contrast to the benzazepine (R)-1. Least-squares fitting of the energy-minimized structures with SYBYL molecular modeling software showed (S)-(+)-2, rather than (R)-(-)-2, gave a better fit to (R)-1. Volume determinations derived from SYBYL multifit analyses aided in receptor mapping to qualitatively describe areas of "active" pharmacophore space as well as areas of "inactive" substituent space.(ABSTRACT TRUNCATED AT 400 WORDS)

Common receptors for hallucinogens in rat brain: a comparative autoradiographic study using [125I]LSD and [125I]DOI, a new psychotomimetic radioligand

The S and R enantiomers of the psychotomimetic 5HT2 agonist DOI (2,5-dimethoxy-4-iodophenylisopropylamine) were labeled with 125I at high-specific activity. The regional distribution of binding sites for each of the enantiomers was investigated using in vitro quantitative autoradiography and compared to the regional distribution of [125I]LSD in the rat brain. Saturable, specific binding of the radioligands was determined in cortical membrane homogenates. All radioligands exhibited specific binding in localized regions throughout the rat brain. Binding of [125I]DOI enantiomers was completely displaced (greater than 90%) by 1 microM of the corresponding unlabeled enantiomer; [125I]LSD was completely displaced by 1 microM LSD. The choroid plexus showed the highest-density binding. Other regions showing high-density binding included the frontoparietal cortex (motor and somatosensory areas), anterior cingulate gyrus, lateral olfactory tubercle, nucleus accumbens, caudate nuclei, claustrum, nucleus of the lateral olfactory tract, dentate gyrus, mamillary nuclei, and motor trigeminal nuclei. In most regions, [125I]S-DOI, the less active enantiomer, exhibited 25-40% of the amount of total binding as [125I]R-DOI. In some regions, [125I]R-DOI and [125I]LSD had similar binding densities; in others, marked differences were apparent. The regional distribution of specific [125I]R-DOI binding sites correlated with the distribution of 5HT2 receptors reported in previous studies. DOI and its analogs may have potential clinical applications for in vivo localization of 5HT2-receptors using positron emission tomography (PET) and similar techniques.

Synthesis and pharmacological characterization of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines as dopamine receptor ligands

A series of 1-phenyl-, 4-phenyl-, and 1-benzyl-1,2,3,4-tetrahydroisoquinolines have been prepared as ring-contracted analogues of the prototypical D1 dopamine receptor antagonist SCH23390 [(R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H- 3-benzazepine]. The affinity and selectivity of these isoquinolines for D1 receptors was determined by three biochemical endpoints in membrane homogenates prepared from rat corpus striatum: the potency to complete for [3H]SCH23390 binding sites; the potency to compete for [3H]spiperone (a D2 receptor ligand) binding sites; and effects on dopamine-stimulated adenylate cyclase. Competitive binding measurements at D1 sites showed SCH23390 to possess the highest affinity, followed by 1-phenyl greater than 1-benzyl greater than 4-phenyl for the isoquinolines. These results were highly correlated with the ability of the test compounds to antagonize dopamine-stimulated adenylate cyclase (r = 0.98). None of the compounds alone stimulated cAMP formation at concentrations of 10 nM to 100 microM. D2 competition binding showed the 1-benzyl derivative to possess the highest affinity, followed by 4-phenyl greater than SCH23390 greater than 1-phenyl. The tertiary 1-phenyl derivative was more potent than the secondary 1-phenyl analogue in all assays. Interestingly, resolution and single-crystal X-ray analysis of the tertiary N-methyl-1-phenyltetrahydroisoquinoline showed the most active enantiomer to possess the S absolute configuration, in contrast to the benzazepine (R)-SCH23390.

(R)-(-)-[77Br]4-bromo-2,5-dimethoxyamphetamine labels a novel 5-hydroxytryptamine binding site in brain membranes

(R)-(-)-[77Br]4-Bromo-2,5-dimethoxyamphetamine [(R)-(-)-[77Br] DOB] was synthesized to a high specific activity (1875 +/- 50 Ci/mmol) and used to label membrane-associated recognition sites in rat brain. (R)-(-)-[77Br]DOB displayed high affinity (KD = 0.60 +/- 0.08 nM) for a relatively low density of binding sites (Bmax = 1.2 +/- 0.08 pmol/g of tissue) in rat cortical membranes as compared with [3H]ketanserin (KD = 0.65 +/- 0.1 nM; Bmax = 6.2 +/- 0.6 pmol/g of tissue). Guanine, but not adenine, nucleotides were found to inhibit specific (R)-(-)-[77Br]DOB binding. GTP (10(-4) M) did not eliminate specific (R)-(-)-[77Br]DOB binding but caused a competitive inhibition of the radioligand. Drug competition studies of 5-hydroxytryptamine (5-HT) and related agents indicate that both putative agonists and antagonists display nanomolar potency for these sites. A significant correlation (p less than 0.01) exists between drug potencies for (R)-(-)-[77Br]DOB-labeled sites and both 5-HT2 (r = 0.64) and 5-HT1C (r = 0.68) binding sites. However, the sites do not appear to be identical. Moreover, a significant correlation exists between drug potencies for (R)-(-)-[77Br]DOB-labeled sites and human hallucinogenic drug potencies (r = 0.89; p less than 0.01). We conclude that (R)-(-)-[77Br]DOB labels a unique 5-HT recognition site in rat brain that does not coincide with previously described 5-HT binding site subtypes. The (R)-(-)-[77Br]DOB site does not appear to be a high affinity "state" of the 5-HT2 receptor but may label a subset of heterogeneous 5-HT2 recognition sites.

A point mutation in the coding sequence of the beta-hexosaminidase alpha gene results in defective processing of the enzyme protein in an unusual GM2-gangliosidosis variant

cDNA clones were isolated from cultured fibroblasts of a patient previously reported as having GM2-gangliosidosis due to defective processing of the precursor beta-hexosaminidase alpha chain. Sequence analysis of a clone containing the entire protein coding sequence showed a single nucleotide substitution, from G to A, at nucleotide residue no. 1444, which resulted in a change in amino acid residue no. 482, from the normal glutamic acid to lysine. This transversion was confirmed in two other cDNAs from the same unamplified library. The results collectively indicate that the change from the strongly negative to strongly positive charge at amino acid residue no. 482 is responsible for the defective processing of the enzyme in this patient.

Synthesis and serotonin receptor affinities of a series of enantiomers of alpha-methyltryptamines: evidence for the binding conformation of tryptamines at serotonin 5-HT1B receptors

A procedure for the preparation of optically pure alpha-methyltryptamines (AMTs) from substituted indoles was developed. The key step in the sequence was the reductive amination of substituted indole-2-propanones with the commercially available pure enantiomers of alpha-methylbenzylamine, followed by the chromatographic separation of the resulting pair of diastereomeric amines by preparative centrifugal (Chromatotron) chromatography. Catalytic N-debenzylation then afforded the pure AMT enantiomers. Optical purity was established by chiral HPLC analysis of the 2-naphthoylamide derivatives. An improved procedure for the preparation of indole-2-propanones was also developed. To probe structure-activity relationships of serotonin receptors, affinities of the alpha-methyltryptamine enantiomers were then measured at the 5-HT2 antagonist receptor subtype, with displacement of [3H]ketanserin, and were estimated at the 5-HT1B receptor, with displacement of [3H]serotonin, respectively, in rat frontal cortex homogenates. Enantioselectivity at the receptor subtypes varied, depending on aromatic substituents. For a 5-hydroxy or 5-methoxy, the S enantiomer had higher affinity or was equipotent to the R enantiomer. This selectivity at [3H]serotonin binding sites was reversed for 4-oxygenated alpha-methyltryptamines, where a 4-hydroxy or 4-methoxy did not enhance affinity over the unsubstituted compounds. These results can be explained, for the [3H]serotonin displacement data, if the binding conformation is one where the ethylamine side chain is trans and lying in a plane perpendicular to the indole ring plane.

Binding to the serotonin 5-HT2 receptor by the enantiomers of 125I-DOI

Preliminary receptor binding experiments with the stereoisomers of 125I-DOI, a new putative 5-HT2 agonist ligand, were conducted. The results indicated specific binding for both enantiomers, with a two-site model giving the best fit to the binding data. R-125I-DOI showed a high affinity dissociation constant of 1.26 nanoMolar, while the less active S-enantiomer had a two-fold lower affinity. Competition experiments with several 5-HT2 agonists also indicated a two site model, with high affinity inhibition constants less than 10 nanoMolar. These results show a stereoselective effect of ligand binding to the 5-HT2 receptor. The use of this ligand to investigate agonist-receptor interactions could be instrumental in the elucidation of the role of serotonergic systems in the mechanism of action of hallucinogens.

Effects of the enantiomers of MDA, MDMA and related analogues on [3H]serotonin and [3H]dopamine release from superfused rat brain slices

The primary amines 3,4-methylenedioxyamphetamine (MDA), and 1-(1,3-benzodioxol-5-yl)-2-butanamine (BDB) were measured for efficacy in release of [3H]serotonin (5-HT) from rat hippocampal slices, and release of [3H]dopamine (DA) from rat caudate nucleus slices. The N-methyl derivatives of MDA and BDB, MDMA and MBDB, respectively, and the optical antipodes of these four agents were compared in this paradigm. All of the test compounds demonstrated a similar efficacy of [3H]5-HT release in the micromolar concentration range. No significant stereoselectivity was seen in measurements of 5-HT release. However, striking differences were found between the test compounds when [3H]DA release was studied. N-methylation of racemic MDA resulted in a decreased ability to release DA, while side chain extension from alpha-methyl to alpha-ethyl completely abolished this activity. Stereoselectivity for the S-(+)-isomers of MDA and MDMA was also demonstrated in the DA release studies. Correlation of these biochemical findings with human subjective reports indicates that serotonin release may play a more important role in the mechanism of action than does dopamine release.

A simple organ bath for electrical stimulation and superfusion of rat brain slices

A simple organ bath was designed for the rapid screening of drugs using electrically stimulated brain slices. Control parameters for the release of 3H-5-HT from rat caudate slices using a simple pulse sequence were developed. Field-stimulated release of serotonin was shown to be calcium dependent and was not inhibited by tetrodotoxin. Preliminary experiments into the inhibition of 3H-5-HT release by lysergic acid diethylamide showed moderate inhibition of electrically stimulated overflow from rat caudate at low concentrations. The ratio of postdrug tritium overflow (S2) to predrug tritium overflow (S1) was determined and used as the measure of inhibition in these experiments. An investigation into drug-stimulated 3H-5-HT release from rat hippocampal slices by methylenedioxyamphetamine revealed significant stimulation of tritium overflow. Overall the new organ bath has fulfilled our need for a rapid central nervous system screening procedure by demonstrating experimental versatility and reproducible results.

Derivatives of 1-(1,3-benzodioxol-5-yl)-2-butanamine: representatives of a novel therapeutic class

The alpha-ethyl phenethylamine derivative 1-(1,3-benzodioxol-5-yl)-2-butanamine was prepared. An asymmetric synthesis was used to prepare the enantiomers of this compound and the related alpha-methyl homologue (MDA). The racemates and enantiomers of both compounds were evaluated in the two-lever drug discrimination assay in rats trained to discriminate saline from 0.08 mg/kg of LSD tartrate. Stimulus generalization occurred with the racemate and the R-(-) enantiomer of the alpha-methyl homologue and the S-(+) enantiomer of the alpha-ethyl primary amine. No generalization occurred with the other enantiomers or with the N-methyl derivatives of either series. Human psychopharmacology studies revealed that the N-methyl derivative of the title compound was nonhallucinogenic and that it had a new, novel psychoactive effect. It is suggested that this compound is the prototype of a new pharmacologic class that may have value in facilitating psychotherapy and that this class be designated as entactogens.

Synthesis and evaluation of 2,3-dihydrobenzofuran analogues of the hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane: drug discrimination studies in rats

Two analogues, 6-(2-aminopropyl)-5-methoxy-2,3-dihydrobenzofuran and 6-(2-aminopropyl)-5-methoxy-2-methyl-2,3-dihydrobenzofuran, of the hallucinogenic agent 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) were synthesized and tested in the two-lever drug discrimination paradigm. In rats trained to discriminate saline from LSD tartrate (0.08 mg/kg), stimulus generalization occurred to both of the 2,3-dihydrobenzofuran analogues but at doses more than 10-fold higher than for DOM. A possible explanation for this dramatic attenuation of LSD-like activity could involve a highly directional electrophilic binding site on the receptor that cannot accept the orientation of the unshared electron pairs on the heterocyclic oxygen atom in the benzofurans.

Synthesis and LSD-like discriminative stimulus properties in a series of N(6)-alkyl norlysergic acid N,N-diethylamide derivatives

A convenient method for the synthesis of N(6)-alkyl norlysergic acid N,N-diethylamide derivatives was developed. A series of these compounds was synthesized and tested for substitution in the two-lever drug discrimination assay, in rats trained to discriminate injections of d-LSD tartrate (185.5 nmol/kg, ip) from saline. A dose-response curve for each of the compounds in the series was generated. Structure-activity relationships were developed, based on comparison of the estimated ED50 values from these curves. Of the compounds that substituted for LSD, the N(6)-ethyl and -allyl were approximately 2-3 times more potent than LSD itself. The N(6)-propyl was equipotent to LSD, while the isopropyl derivative was half as active. The n-butyl compound was 1 order of magnitude less potent than LSD, suggesting a similarity to the SAR of certain serotonin and dopamine agonists. By contrast, no generalization occurred to norlysergic acid N,N-diethylamide and the N(6)-2-phenethyl derivative.

C(2)-Methylation abolishes DA1 dopamine agonist activity of 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN): steric intolerance by the receptor

The synthesis of 2-amino-2-methyl-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene is reported. This compound did not produce vasodilation in the dog renal artery and was inactive as a DA1-type dopamine agonist. This is in contrast to the 2-nonmethylated homologue 6,7-ADTN, which is a potent DA1 agonist. High-field 1H NMR studies of the O,O-dimethyl ethers for both compounds as their free bases in chloroform-d revealed that the 2-methyl homologue probably exists as a rapidly equilibrating mixture of conformers; it seems likely that it can adopt the active conformation proposed to be required by the dopamine receptor. The lack of activity is therefore attributed to the steric effect of the 2-methyl group, consistent with explanations offered by others that the dopamine receptor cannot tolerate alkylation at the alpha side-chain carbon.

Effects of certain hallucinogenic amphetamine analogues on the release of [3H]serotonin from rat brain synaptosomes

The enantiomers of 3,4-(methylenedioxy)amphetamine (MDA), p-methoxyamphetamine (PMA), and N-Me-MDA (MDMA), along with their alpha, alpha-dimethylated derivatives, were evaluated for an effect on the release of [3H]serotonin from rat whole brain synaptosomes. The amphetamine isomers were all potent in inducing the release of [3H]serotonin at bath concentrations of 1 and 10 micrometers but were inactive at 0.1 micrometers. No significant difference in isomer potency was observed at the 10 micrometers concentration. However, at 1 micrometer the (+) isomer of MDMA was more effective in inducing release than was the (-) isomer. Since it is the (+) isomer which is clinically active, this result suggests that transmitter release may play a role in the biological activity of MDMA. By contrast, the alpha, alpha-dimethyl compounds were not effective in releasing serotonin, even at the highest bath concentration.