Catecholaminergic Activity Enhancer Research Articles

Enhancer Regulation of Dopaminergic Neurochemical Transmission in the Striatum.

The trace amine-associated receptor 1 (TAAR1) is a Gs protein-coupled, intracellularly located metabotropic receptor. Trace and classic amines, amphetamines, act as agonists on TAAR1; they activate downstream signal transduction influencing neurotransmitter release via intracellular phosphorylation. Our aim was to check the effect of the catecholaminergic activity enhancer compound ((−)BPAP, (R)-(−)-1-(benzofuran-2-yl)-2-propylaminopentane) on neurotransmitter release via the TAAR1 signaling. Rat striatal slices were prepared and the resting and electrical stimulation-evoked [3H]dopamine release was measured. The releaser (±)methamphetamine evoked non-vesicular [3H]dopamine release in a TAAR1-dependent manner, whereas (−)BPAP potentiated [3H]dopamine release with vesicular origin via TAAR1 mediation. (−)BPAP did not induce non-vesicular [3H]dopamine release. N-Ethylmaleimide, which inhibits SNARE core complex disassembly, potentiated the stimulatory effect of (−)BPAP on vesicular [3H]dopamine release. Subsequent analyses indicated that the dopamine-release stimulatory effect of (−)BPAP was due to an increase in PKC-mediated phosphorylation. We have hypothesized that there are two binding sites present on TAAR1, one for the releaser and one for the enhancer compounds, and they activate different PKC-mediated phosphorylation leading to the evoking of non-vesicular and vesicular dopamine release. (−)BPAP also increased VMAT2 operation enforcing vesicular [3H]dopamine accumulation and release. Vesicular dopamine release promoted by TAAR1 evokes activation of D2 dopamine autoreceptor-mediated presynaptic feedback inhibition. In conclusion, TAAR1 possesses a triggering role in both non-vesicular and vesicular dopamine release, and the mechanism of action of (−)BPAP is linked to the activation of TAAR1 and the signal transduction attached.

A longevity study with enhancer substances (selegiline, BPAP) detected an unknown tumor-manifestation-suppressing regulation in rat brain

AimsFirst proof to show that (−)-deprenyl/selegiline (DEP), the first selective inhibitor of MAO-B, later identified as the first β-phenylethylamine (PEA)-derived synthetic catecholaminergic activity enhancer (CAE) substance and (2R)-1-(1-benzofuran-2-yl)-N-propylpentane-2-amine (BPAP), the tryptamine-derived presently known most potent, selective, synthetic enhancer substance, are specific markers of unknown enhancer-sensitive brain regulations. Main methodsLongevity study disclosing the operation of tumor-manifestation-suppressing (TMS) regulation in rat brain. Immonohistochemical identification of a fibromyxosarcoma in rats. Experiments with human medulloblastoma cell lines. Analysis of the mechanism of action of enhancer substances. Key findingsWhereas 20/40 saline-treated rats manifested a fibromyxosarcoma, in groups of rats treated with 0.001mg/kg DEP: 15/40 rats; with 0.1mg/kg DEP: 11/40 rats (P<0.01); with 0.0001mg/kg BPAP: 8/40 rats (P<0.001); with 0.05mg/kg BPAP: 7/40 rats (P<0.01) manifested the tumor. Experiments with human medulloblastoma cell lines, HTB-186 (Daoy); UW-228-2, showed that BPAP was devoid of direct cytotoxic effect on tumor cells, and did not alter the direct cytotoxic effectiveness of temozolomide, cisplatin, etoposide, or vincristine. Interaction with distinct sites on vesicular monoamine-transporter-2 (VMAT2) is the main mechanism of action of the enhancer substances which clarifies the highly characteristic bi-modal, bell-shaped concentration-effect curves of DEP and BPAP. SignificanceConsidering of the safeness of the enhancer substances and the finding that DEP and BPAP, specific markers of unknown enhancer sensitive brain regulations, detected the operation of an enhancer-sensitive TMS-regulation in rat brain, it seems reasonable to test in humans low dose DEP or BPAP treatment against the spreading of a malignant tumor.

Longevity study with low doses of selegiline/(−)-deprenyl and (2R)-1-(1-benzofuran-2-yl)-N-propylpentane-2-amine (BPAP)

Aims: The first longevity study demonstrating that rats treated with the MAO-B inhibitory dose of (−)-deprenyl (0.25mg/kg) lived significantly longer than their saline-treated peers was published in 1988, and corroborated in many papers. The recent findings that (−)-deprenyl is primarily a PEA-derived synthetic catecholaminergic activity enhancer substance; (2R)-1-(1-benzofuran-2-yl)-N-propylpentane-2-amine (BPAP) is a tryptamine-derived synthetic enhancer substance, initiated our first longevity study on rats with low enhancer doses of (−)-deprenyl and BPAP to test the enhancer effect's role in life extension.Main methods: We used the shuttle box technique for selecting the optimum doses of (−)-deprenyl and BPAP. (−)-Deprenyl exerts in rats in 0.001mg/kg its ‘specific’ enhancer effect and in 0.1mg/kg its ‘non-specific’ enhancer effect. BPAP exerts its ‘specific’ enhancer effect in 0.0001mg/kg and its ‘non-specific’ enhancer effect in 0.05mg/kg. Groups of male Wistar rats (N=40) were treated subcutaneously from their 10th week until death, three times weekly, with saline (0.5ml/kg), and the selected doses of (−)-deprenyl or BPAP, respectively. As an indicator of aging we tested the age-related changes in their learning ability.Key findings: Rats treated with 0.0001 or 0.05mg/kg BPAP lived significantly longer than their saline treated peers (P<0.02) and BPAP was more potent in extending rats' lifespan than (−)-deprenyl. 18-month-old rats treated with 0.0001mg/kg BPAP were as good learners as 3-month-old saline treated rats. SignificanceThe study revealed that the enhancer effect is responsible for life extension.

The significance of selegiline/(-)-deprenyl after 50 years in research and therapy (1965-2015).

Deprenyl/Selegiline (DEP), created by Joseph Knoll in the 1960s, registered in more than 60 countries to treat Parkinson's disease, Alzheimer's disease, major depressive disorder; and used as an anti-aging drug, achieved its place in research and therapy as the first selective inhibitor of B-type monoamine oxidase (MAO-B). The demonstration that the DEP analog (-)-1-phenyl-2-propylaminopentane devoid of MAO inhibitory property, enhanced like DEP the activity of the catecholaminergic brain engine revealed that this effect is unrelated to the selective inhibition of MAO-B. β-Phenylethylamine (PEA), the important trace-amine in the mammalian brain, is known to be a releaser of catecholamines. Amphetamine and methamphetamine, the best known synthetic PEA derivatives are also releasers of catecholamines like their parent compound. DEP is a unique synthetic PEA derivative devoid of the catecholamine releasing property. As the releasing effect conceals the catecholaminergic activity enhancer (CAE) effect, it remained undiscovered until DEP uncovered that PEA is a natural CAE substance; and only releases catecholamines in high concentration. Discovering that tryptamine is a natural enhancer of catecholaminergic and serotonergic neurons catalyzed the development of R-(-)-1-(benzofuran-2-yl)-2-propylaminopentane (BPAP); the most potent and selective enhancer substance, and it exerts its enhancer effect in 0.0001 mg kg-1. DEP and BPAP initiated an analysis of the enhancer regulation in the mammalian brain. Studies regarding the nature of the enhancer regulation revealed that this regulation is enhanced after weaning and sex hormones return it to the pre-weaning level. Thus, sex hormones elicit the transition of the developmental phase of life into the post-developmental, downhill (aging) period. The aging-related, slow decline in the enhancer regulation of the catecholaminergic brain engine, the main activator of the cortex, is the prime factor of brain aging. The enhancer regulation's decay in the most rapidly aging dopaminergic system is, for example, mainly responsible for the decline in learning ability and sexual activity over time. According to the Knoll concept, based on two longevity studies performed on male rats, to keep the catecholaminergic brain engine, from the beginning of the downhill period of life, via the administration of a small daily dose of a CAE substance (presently DEP is the only available drug) on a higher activity level, thus to fight against the physiological aging-related slow decay of the catecholaminergic system, is a suitable anti-aging therapy. As our present knowledge regarding the enhancer regulation in the mammalian brain is like seeing a peak of an iceberg, the future of this new line of brain research looks promising from both theoretical and practical aspects.

Essential difference between the pharmacological spectrum of (−)-deprenyl and rasagiline

Background(−)-Deprenyl and rasagiline are classified as selective inhibitors of B-type MAO. The DATATOP study revealed that the administration of (−)-deprenyl to untreated patients with Parkinson's disease (PD) significantly delays the need for levodopa therapy (Parkinson Study Group, 1989). Rasagiline was ineffective in this respect (Parkinson Study Group, 2002). The aim of this paper is to explain the reasoning behind the differentiation between (−)-deprenyl and rasagiline. MethodsIn the shuttle box the acquisition of a two way conditioned avoidance response (CAR) was analyzed on male Wistar rats during 5 consecutive days. Tetrabenazine-treatment (1mg/kg sc) depletes the transmitters from their stores in the nerve terminals of the catecholaminergic neurons and blocks the acquisition of a CAR. Catecholaminergic activity enhancer (CAE) substances [(−)-deprenyl, (−)-BPAP] fully antagonize the tetrabenazine-induced learning deficit. Using (−)-deprenyl and (−)-BPAP as reference substances, we measured the effect of rasagiline and J-508 in this test. Rasagiline is the desmethyl-analog of J-508, described by Knoll in 1978. ResultsIn contrast to (−)-deprenyl and (−)-BPAP, J-508 and rasagiline were found in the shuttle box test to be devoid of the CAE effect. ConclusionsSince convincing experimental and clinical evidence speaks in favor for the conclusion that the catecholaminergic activity enhancer (CAE) effect of (−)-deprenyl is responsible for the significantly delayed need for levodopa therapy in untreated patients with PD (Knoll, 2012) and rasagiline is devoid of the CAE effect, this might explain why “…based on current evidence, rasagiline cannot be said to definitely have a disease-modifying effect” [Robottom, 2011].

Enantioselective synthesis and absolute configuration of (−)-1-(benzofuran-2-yl)-2-propylaminopentane, ((−)-BPAP), a highly potent and selective catecholaminergic activity enhancer

Enantioselective synthesis and absolute configuration of (−)-1-(benzofuran-2-yl)-2-propylaminopentane ((−)-BPAP), which is a highly potent and selective catecholaminergic activity enhancer (CAE) substance, are described. The synthetic approach consists of the coupling reaction of benzofuran with ( R)- N-tosyl-2-propylazirizine or ( R)- N-methoxy- N-methylnorvaliamide, followed by appropriate modifications of the resulting coupling products. As the results, (−)-BPAP turned out to have the R configuration, which was finally confirmed by X-ray crystallographic analysis.

(-)Deprenyl (selegiline), a catecholaminergic activity enhancer (CAE) substance acting in the brain.

beta-Phenylethylamine and its long acting derivatives, the amphetamines, are mixed-acting stimulants of the sympathetic system in the brain. They enhance the impulse propagation mediated release of catecholamines (catecholaminergic activity enhancer effect) and displace catecholamines from their stores (catecholamine releasing effect). (-)Deprenyl (selegiline), a close structural relative to (-)methamphetamine, is the first catecholaminergic activity enhancer substance in clinical use devoid of catecholamine releasing property, being therefore free of the 'cheese effect' and of the dependence capacity of the amphetamines. (-)Deprenyl is also a highly potent and selective, irreversible inhibitor of monoamine oxidase type B. (-)Deprenyl enhances superoxide dismutase and catalase activity in the striatum, protects the nigrostriatal dopaminergic neurons against selective neurotoxins (6-hydroxy-dopamine, MPTP, 4-N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine) and prevents characteristic age-related morphological changes in the neurocytes of the substantia nigra. Maintenance of rats on (-)deprenyl during the postdevelopmental phase of their life slows the age-related decline of sexual and learning performances and prolongs life significantly. Patients with early, untreated Parkinson's disease maintained on (-)deprenyl need levodopa significantly later than their placebo-treated peers, and when on levodopa plus (-)deprenyl, they live significantly longer than patients on levodopa alone. In patients with moderately severe impairment from Alzheimer's disease, treatment with (-)deprenyl slows the progression of the disease. It may be supposed that a prophylactic low dose administration of a safe catecholaminergic activity enhancer substance during the postdevelopmental phase of life will slow the age-related decline of behavioral performances, delay natural death and decrease susceptibility to Parkinson's disease and Alzheimer's disease.

Sexual performance and longevity.

Sexually inactive ("low-performing," LP) and highly active ("high-performing," HP) rats were selected from a sexually inexperienced population. Saline control LP rats (n = 44) lived 134.58 +/- 2.29 weeks, their HP peers (n = 49) lived 151.24 +/- 1.36 weeks. Life-long treatment with 0.25 mg/kg (-)deprenyl, a selective inhibitor of MAO-B that also stimulates action potential-transmitter release coupling in the catecholaminergic neurons in the brain (catecholaminergic activity enhancer, CAE, effect), enhanced the sexual and learning performance of both LP and HP rats and prolonged their life. LP rats (n = 48) treated with (-)deprenyl lived 152.54 +/- 1.36 weeks and HP rats on (-)deprenyl (n = 50) lived 185.30 +/- 1.96 weeks. As an indicator of the basic activity of catecholaminergic neurons, the resting release of dopamine from the striatum, substantia nigra, and tuberculum olfactorium, and of norepinephrine from the locus coeruleus, was measured in 2-, 4-, 8-, 16-, and 32-week-old male and female rats. The release of transmitters between weaning and the second month of age, i.e., during the crucial developmental phase of life, was significantly higher than either before or after that period, indicating that a CAE mechanism starts working with high intensity after weaning, lasts until the completion of full scale sexual development, and shows an unparalleled decay thereafter. It was concluded that the CAE regulation in the brain, stimulated by (-)deprenyl, controls general activity and consequently the longevity of rats.

Phenylethylamine and tyramine are mixed-acting sympathomimetic amines in the brain

On the helical strip of a capacitance vessel, the pulmonary artery of the rabbit, phenylethylamine (PEA) and tyramine act solely via displacement of noradrenaline from their storage sites and this effect is inhibited by desmethylimipramine (DMI). In contrast, on a resistance vessel, the perfused central ear artery of the rabbit, PEA enhances stimulation induced contractions in 0.2–0.8 gmg/ml concentration [catecholaminergic activity enhancer (CAE) effect], and increases smooth muscle tone (noradrenaline displacing effect) in 4–6 μg/ml concentration. This latter effect only is blocked by DMI. Tyramine acts similarly and is more potent than PEA. On the isolated brain stem PEA, tyramine and (-)methamphetamine are, in the presence of cocaine and DMI, highly potent enhancers of stimulation induced release of 3H-noradrenaline, 3H-dopamine and 3H-serotonin. Compounds with specific CAE effect in the brain, (-)deprenyl and l-phenyl-2-propylaminopentane [(-)PPAP], antagonize tetrabenazine-induced depression of performance of rats in the shuttle box. PEA and tyramine, which are rapidly metabolized in vivo, are ineffective in this test up to 40 mg/kg, whereas (-)methamphetamine, the stable PEA derivative, is highly effective. Compounds with CAE effect enhance at low concentrations the slow inward Ca 2+ current in the sino-auricular fibers of the frog heart and inhibit it in high concentration. PEA and tyramine enhance Ca 2+ influx from 0.05 to 4 μg/ml and inhibit it in 8 μg/ml. In conclusion, PEA and tyramine stimulate primarily coupling of action potential to transmitter release in the catecholaminergic neurons in the brain and displace catecholamines in higher concentration only.

High performing rats are more sensitive toward catecholaminergic activity enhancer (CAE) compounds than their low performing peers

Two breeds of rats, Charles River Wistar [Crl (Wi) Br.] and HSD Wistar [Wistar per LATI (Budapest) Br.], with remarkable difference in learning performance were selected. The rats were trained in the shuttle box with 100 trials per day and the number of conditioned avoidance responses (CARs), the escape failures (EFs) to the unconditioned stimulus and the intersignal reactions (IRs) were counted and evaluated by multi-way analysis of variance (ANOVA). Rats of the Crl (Wi) breed proved to be the ‘low performing’ (LP) animals and rats of the Wistar per LATI (Budapest) breed the ‘high performing’ (HP) ones. The HP rats produced higher number of CARs (p < 0.001), lower number of EFs (p < 0.05) and higher number of IRs (p < 0.01) than their LP peers. Significantly higher amounts of noradrenaline from the locus coeruleus and serotonin from the raphe were released in the HP than in the LP rats (p < 0.01). There was no difference between HP and LP rats in the amount of dopamine released from the striatum, the substantia nigra and the tuberculum olfactorium. The catecholaminergic activity enhancer (CAE) substance, l-phenyl-2-propylaminopentane HCl,, [(−)PPAP], which enhances action potentialtransmitter release coupling in the catecholaminergic neurons, fully antagonized in a dose of 1 mg/kg, tetrabenazme-induced learning depression in HP rats and this dose was ineffective in LP rats. The findings were regarded as further support for the view that endogenous CAE substances regulate catecholaminergic activity in the brain and (−)PPAP acts via this regulation.

(−)Deprenyl and (−)1-phenyl-2-propylaminopentane, [(−) PPAP] act primarily as potent stimulants of action potential — transmitter release coupling in the catecholaminergic neurons

The activity of the catecholaminergic neurons in the rat brain is enhanced significantly 30 min after the subcutaneous injection of very small doses of (−)deprenyl (threshold doses: 0.01 mg/kg for noradrenergic neurons and 0.025 mg/kg for dopaminergjc neurons). As a catecholaminergic activity enhancer (CAE) substance (−)deprenyl is about ten times more potent than its parent compound, (−)methamphetamine. While the (+)methamphetamine is 3–5 times more potent than (−)methamphetamine in releasing catecholamines, the (−)methamphetamine is the more potent CAE substance. The mechanism of the CAE effect of (−)deprenyl and (−)PPAP, a deprenyl-derived substance devoid of MAO inhibitory potency, was studied in rats by measuring: a) the release of catecholamines from striatum, substantia nigra, tuberculum olfactorium and locus coeruleus; b) the stimulation induced release of 3H-noradrenaline from the isolated brain stem; and c) the antagonistic effect against tetrabenazine-induced depression of learning in the shuttle box. The CAE effect was found to be unrelated: a) to the inhibition of MAO activity; b) to the inhibition of presynaptic catecholamine receptors; c) to the inhibition of the uptake of catecholamines; and d) to the release of catecholamines. It was concluded that (−)deprenyl and (−)PPAP act primarily as potent stimulants of action potential-transmitter release coupling in the catecholaminergic neurons of the brain. We show that both (−)deprenyl and (−)PPAP enhance the inward Ca 2+ current in sino-auricular fibers of the frog heart. (−)PPAP was much more potent than either (+)PPAP or (−)deprenyl in this test.