Chronic treatment with enhancer drugs modifies the gene expression of selected parameters related to brain plasticity in rats under stress conditions.

Selegiline, also known as L-deprenyl, and (2R)-1-(1-benzofuran-2-yl)-N-propylpentane-2-amine (BPAP) were found to induce enhancement of monoamine neurotransmission in low and very low doses. In addition, these enhancers may modify glutamatergic neurotransmission. The aim of the present study was to test the hypothesis that under stress conditions, chronic treatment with enhancer drugs has a positive impact on the glutamatergic system and other parameters related to brain plasticity, stress-related systems, and anxiety behavior. We exposed male Wistar rats to a chronic mild stress procedure combined with chronic treatment with two synthetic enhancer drugs. The gene expression of GluR1, an AMPA receptor subunit was reduced by repeated treatment with deprenyl in the hippocampus and with both BPAP and deprenyl in the prefrontal cortex. A significant reduction of NMDA receptor subunit GluN2B expression was observed in the hippocampus but not in the prefrontal cortex. Deprenyl treatment led to an enhancement of hippocampal BDNFmRNA concentrations in stress-exposed rats. Treatment with enhancer drugs failed to induce significant changes in stress hormone concentrations or anxiety behavior. In conclusion, the present study in chronically stressed rats showed that concomitant treatment with enhancer drugs did not provoke substantial neuroendocrine changes, but modified gene expression of selected parameters associated with brain plasticity. Observed changes may indicate a positive influence of enhancer drugs on brain plasticity, which is important for preventing negative consequences of chronic stress and enhancement of stress resilience. It may be suggested that the changes in glutamate receptor subunits induced by enhancer drugs are brain region-specific and not dose-related.

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

AIMS: First proof to show that (-)-deprenyl/selegiline (DEP), the first selective inhibitor of MAO-B, later identified as the first ß-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 METHODS: Longevity 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 FINDINGS: Whereas 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. SIGNIFICANCE: Considering 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. SIGNIFICANCE: The 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. ß-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.

Treatment possibilities of Alzheimer's disease.

A brief summary of the current treatment of Alzheimer disease (AD) (cholinergic replacement therapy, influence of glutamatergic neurotransmission, treatment based on the beta-amyloid cascade theory, antioxidants, anti-inflammatory drugs) clearly proves that the applied strategies are practically inefficient. We describe therefore the rationale and design of a reasonable clinical trial to test the validity of Knoll's concept that the administration of a synthetic mesencephalic enhancer substance prior to the precipitation of the symptoms is our only chance to significantly reduce the prevalence of the two main neurodegenerative disorders AD and Parkinson's disease (PD). Considering that in the population over 65 there are substantial sex (68% female, 32% male) and geographical (highest rate: 10% in USA) differences in the incidence of AD, we propose to perform the clinical trial in 75-85 year old females in the USA. Individuals without (Group 1) and with (Group 2) predisposition to AD should be selected. One third in each group should be treated daily with placebo, (-)-deprenyl (1 mg) and (-)-BPAP (1 mg), respectively. Series of studies proved already the protective effect of the synthetic mesencephalic enhancer substances against age-related neurodegenerative changes in the brain. We may therefore expect a significant difference in the placebo versus drug treated groups in the number of individuals who will precipitate with the passing of time the symptoms of AD or PD. The introduction of a safe and efficient prophylactic therapy that significantly decreases the prevalence of AD is a necessity which cannot be further postponed.

Analysis of the effect of (-)-BPAP, a selective enhancer of the impulse propagation mediated release of catecholamines and serotonin in the brain.

Endogenous and synthetic enhancer substances enhance in low concentration the impulse propagation mediated release of transmitters from the catecholaminergic and serotonergic neurons in the brain. The purpose of this study was to see whether uptake or MAO inhibition or agonists have similar enhancing prospectives as the enhancer substances. We measured the electrical stimulation induced release of [3H]-norepinephrine or [3H]-dopamine or [3H]-serotonin from the isolated brain stem of rats. (-)-1-Benzofuran-2-yl)-2-propylaminopentane HCl [(-)-BPAP] was used as a prototype of the enhancer compounds. 50 ng/ml (-)-BPAP was the most effective concentration in enhancing the nerve stimulation induced release of [3H]-norepinephrine and [3H]-dopamine, 10 ng/ml (-)-BPAP was highly effective in enhancing the release of [3H]-serotonin. In contrast, 250 ng/ml desmethylimipramine (DMI), a selective inhibitor of the uptake of norepinephrine, did not change significantly the nerve stimulation induced release of [3H]-norepinephrine and 50 ng/ml fluoxetine, a selective inhibitor of the uptake of serotonin, did not change the release of [3H]-serotonin. Neither 250 ng/ml clorgyline, a selective inhibitor of MAO-A, nor 250 ng/ml lazabemide, a selective inhibitor MAO-B, was capable to significantly increase the nerve stimulation induced release of either [3H]-serotonin or [3H]-norepinephrine. The potent dopamine receptor agonists, pergolide and bromocriptine did not change significantly the release of [3H]-dopamine in 50 ng/ml concentration, which is sufficient to stimulate the dopamine receptors. The results prove that stimulation of catecholaminergic and serotonergic neurons in the brain via the enhancing mechanism is clearly different from influencing uptake or MAO.

An HPLC tracing of the enhancer regulation in selected discrete brain areas of food-deprived rats.

The recent discovery of the enhancer regulation in the mammalian brain brought a different perspective to the brain-organized realization of goal-oriented behavior, which is the quintessence of plastic behavioral descriptions such as drive or motivation. According to this new approach, 'drive' means that special endogenous enhancer substances enhance the impulse-propagation-mediated release of transmitters in a proper population of enhancer-sensitive neurons, and keep these neurons in the state of enhanced excitability until the goal is reached. However, to reach any goal needs the participation of the catecholaminergic machinery, the engine of the brain. We developed a method to detect the specific enhancer effect of synthetic enhancer substances [(-)-deprenyl, (-)-PPAP, (-)-BPAP] by measuring the release of transmitters from freshly isolated selected discrete brain areas (striatum, substantia nigra, tuberculum olfactorium, locus coeruleus, raphe) by the aid of HPLC with electrochemical detection. To test the validity of the working hypothesis that in any form of goal-seeking behavior the catecholaminergic and serotonergic neurons work on a higher activity level, we compared the amount of norepinephrine, dopamine, and serotonin released from selected discrete brain areas isolated from the brain of sated and food-deprived rats. Rats were deprived of food for 48 and 72 hours, respectively, and the state of excitability of their catecholaminergic and serotonergic neurons in comparison to that of sated rats was measured. We tested the orienting-searching reflex activity of the rats in a special open field, isolated thereafter selected discrete brain areas and measured the release of norepinephrine, dopamine, and serotonin from the proper tissue samples into the organ bath. The orienting-searching reflex activity of the rats increased proportionally to the time elapsed from the last feed and the amount of dopamine released from the striatum, substantia nigra and tuberculum olfactorium, that of norepinephrine released from the locus coeruleus and that of serotonin released from the raphe increased significantly in the hungry rats proportionally to the time of fasting. For example: the amount of dopamine released from the substantia nigra of sated rats (4.62 +/- 0.20 nmoles/g wet weight) increased to 5.95 +/- 0.37 (P < 0.05) and 10.67 +/- 0.44 (P < 0.01) in rats deprived of food for 48 and 72 hours, respectively.

A pharmacological analysis elucidating why, in contrast to (-)-deprenyl (selegiline), alpha-tocopherol was ineffective in the DATATOP study.

The Parkinson Study Group who conducted the Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) trial designed their study in the belief that the MAO inhibitor (-)-deprenyl (selegiline), the antioxidant alpha-tocopherol, and the combination of the two compounds will slow the clinical progression of the disease to the extent that MAO activity and the formation of oxygen radicals contribute to the pathogenesis of nigral degeneration. In fact, (-)-deprenyl only delayed the onset of disability associated with early, otherwise untreated Parkinson's disease, however, in contrast to the expectation of the authors, alpha-tocopherol proved to be ineffective in the DATATOP study. Enhancer substances, (-)-deprenyl, (-)-1-phenyl-2-propylaminopentane [(-)-PPAP] the (-)-deprenyl analogue free of MAO inhibitory potency, and R-(-)1-(benzofuran-2-yl)-2-propylaminopentane [(-)-BPAP] the presently known most potent enhancer substance, are peculiar stimulants. They enhance the impulse propagation mediated release of the catecholamines in the brain. Due to their enhancer effect, the amount of catecholamines released from selected discrete brain areas (striatum, substantia nigra, tuberculum olfactorium, locus coeruleus) is significantly higher in rats treated with an enhancer substance than in saline treated rats. We compared the effect of (-)-deprenyl 0.025 and 0.25 mg/kg, (-)-PPAP 0.1 mg/kg, (-)-BPAP 0.0001 mg/kg, and alpha-tocopherol 25 and 50 mg/kg, in this test. The doses of (-)-deprenyl and alpha-tocopherol were selected to be in compliance with the dose given in the DATATOP study. Compared to saline treated rats, the enhancer substances significantly increased the amount of dopamine released from the striatum, substantia nigra and tuberculum olfactorium and the amount of norepinephrine released from the locus coeruleus; alpha-tocopherol was ineffective. The results indicate that alpha-tocopherol was ineffective, because, unlike (-)-deprenyl it dose not enhance the activity of the nigrostriatal dopaminergic neurons.

Structure-activity studies leading to (-)1-(benzofuran-2-yl)-2-propylaminopentane, ((-)BPAP), a highly potent, selective enhancer of the impulse propagation mediated release of catecholamines and serotonin in the brain.

The catecholaminergic and serotoninergic neurons in the brain change their performance according to the physiological need via a catecholaminergic/serotoninergic activity enhancer (CAE/SAE) mechanism. Phenylethylamine (PEA), tyramine and tryptamine are the presently known endogenous CAE/SAE substances which enhance the impulse propagation mediated release of catecholamines and serotonin in the brain. A PEA derivative, (-)deprenyl (selegiline), known as a selective inhibitor of MAO-B, is for the time being the only CAE/SAE substance in clinical use. Aiming to develop a selective CAE/SAE substance much more potent than (-)deprenyl, a series of new 1-aryl-2-alkylaminoalkanes, structurally unrelated to PEA and the amphetamines, was designed and prepared. Among them, (-)1-(benzofuran-2-yl)-2-propylaminopentane ((-)BPAP) was selected as a promising candidate substance for further studies. (-)BPAP significantly enhanced in rats the impulse propagation mediated release of catecholamines and serotonin in the brain 30min after acute injection of 0.36nmol/kg sc. In the shuttle box, (-)BPAP was in rats about 130 times more potent than (-)deprenyl in antagonizing tetrabenazine induced inhibition of performance. (+/-)BPAP protected cultured hippocampal neurons from the neurotoxic effect of beta-amyloid in 10(-14)-10(-15)M concentration.

Sexual hormones terminate in the rat: the significantly enhanced catecholaminergic/serotoninergic tone in the brain characteristic to the post-weaning period.

The amount of dopamine released from the striatum, substantia nigra and tuberculum olfactorium, noradrenaline from locus coeruleus and serotonin from the raphe, was significantly higher in four and five weeks old rats than in three month old ones, proving that the catecholaminergic/serotoninergic activity enhancer (CAE/SAE) regulation works unrestrained during developmental longevity and is restricted thereafter. As the dampening of the CAE/SAE regulation (end to the second month of age) coincided temporally with the appearance of sexual hormones, we castrated three weeks old male and female rats and measured at the end of the third month of their life the release of catecholamines and serotonin from selected discrete brain regions. The amount of catecholamines and serotonin released from the neurons was significantly higher in castrated than in untreated or sham operated rats, signalting that sexual hormones inhibit the CAE/SAE regulation in the brain. We therefore treated male and female rats s.c. with oil (0.1 ml/rat), testosterone, (0.1 mg/rat), estrone (0.01 mg/rat) and progesterone (0.5 mg/rat), respectively, and measured their effect on the CAE/SAE regulation. Twenty-four hours after a single injection with the hormones, the release of noradrenaline, dopamine and serotonin was significantly inhibited in the testosterone or estrone treated rats, but remained unchanged after progesteron treatment. In rats treated with a single hormone injection, testosterone in the male and estrone in the female was the significantly more effective inhibitor. Remarkably, the reverse order of potency was found in rats treated with daily hormone injections for 7 or 14 days. After two-week treatment with the hormones estrone was in the male and testosterone in the female the significantly more potent inhibitor of the CAE/SAE regulation. The data indicate that sexual hormones terminate the hyperactive phase of adolescence by dampening the impulse propagation mediated release of catecholamines and serotonin in the brain.

(-)1-(Benzofuran-2-yl)-2-propylaminopentane, [(-)BPAP], a selective enhancer of the impulse propagation mediated release of catecholamines and serotonin in the brain.

1. The brain constituents beta-phenylethylamine (PEA) and tryptamine enhance the impulse propagation mediated transmitter release (exocytosis) from the catecholaminergic and serotoninergic neurons in the brain ('catecholaminergic/serotoninergic activity enhancer, CAE/SAE, effect'). (-)Deprenyl (Selegiline) and (-)1-phenyl-2-propylaminopentane [(-)PPAP] are amphetamine derived CAE substances devoid of the catecholamine releasing property. 2. By changing the aromatic ring in PPAP we developed highly potent and selective CAE/SAE substances, structurally unrelated to the amphetamines. Out of 65 newly synthetized compounds, a tryptamine derived structure, (-)1-(benzofuran-2-yl)-2-propylaminopentane [(-)BPAP] was selected as a potential follower of (-)deprenyl in the clinic and as a reference compound for further analysis of the CAE/SAE mechanism in the mammalian brain. 3. (-)BPAP significantly enhanced in 0.18 micromol 1(-1) concentration the impulse propagation mediated release of [(3)H]-noradrenaline and [(3)H]-dopamine and in 36 nmol 1(-1) concentration the release of [(3)H]-serotonin from the isolated brain stem of rats. The amount of catecholamines and serotonin released from isolated discrete rat brain regions (dopamine from the striatum, substantia nigra and tuberculum olfactorium, noradrenaline from the locus coeruleus and serotonin from the raphe) enhanced significantly in the presence of 10(-12) - 10(-14) M (-)BPAP. BPAP protected cultured hippocampal neurons from the neurotoxic effect of beta-amyloid in 10(-14) M concentration. In rats (-)BPAP significantly enhanced the activity of the catecholaminergic and serotoninergic neurons in the brain 30 min after acute injection of 0.1 microg kg(-1) s.c. In the shuttle box, (-)BPAP in rats was about 130 times more potent than (-)deprenyl in antagonizing tetrabenazine induced inhibition of performance.

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, 1-phenyl-2-propylaminopentane HCl, [(-)PPAP], which enhances action potential-transmitter release coupling in the catecholaminergic neurons, fully antagonized in a dose of 1 mg/kg, tetrabenazine-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 dopaminergic 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 (-)methamphetammine 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 Ca2+ current in sino-auricular fibers of the frog heart. (-)PPAP was much more potent than either (+)PPAP or (-)deprenyl in this test.

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 microgram/ml concentration [catecholaminergic activity enhancer (CAE) effect], and increases smooth muscle tone (noradrenaline displacing effect) in 4-6 micrograms/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 1-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 Ca2+ current in the sino-auricular fibers of the frog heart and inhibit it in high concentration. PEA and tyramine enhance Ca2+ influx from 0.05 to 4 micrograms/ml and inhibit it in 8 micrograms/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.

Enhanced catecholaminergic and serotoninergic activity in rat brain from weaning to sexual maturity: rationale for prophylactic (-)deprenyl (selegiline) medication.

Food deprived rats in the late developmental phase of life (2 months of age) are significantly more active than those in the early postdevelopmental phase (4 months of age), pointing to enhanced catecholaminergic activity during the developmental phase. We therefore measured the resting release of dopamine from the striatum, substantia nigra and tuberculum olfactorium, and of noradrenaline from the locus coeruleus, as an indicator of the basic activity of catecholaminergic neurons in the brain, in 2,4,8,16 and 32 weeks old male and female rats. We also measured the release of serotonin from the raphe. Both in male and female rats, the resting release of transmitters from brain catecholaminergic and serotoninergic neurons between weaning and the end of the 2nd month of age, i.e. during the crucial developmental phase of their life, was significantly higher than either before or after that period, signalling a transition from a developmental to a postdevelopmental (aging) phase of life and indicating that safe and effective measures are needed to maintain the catecholaminergic system at a higher activity level during the postdevelopmental phase. Daily administration of low doses (0.01-0.25 mg/kg) of (-)deprenyl for 21 days significantly enhances the resting release of catecholamines and diminishes that of serotonin, providing a rationale for prophylactic medication with this drug during the postdevelopmental lifespan. We also show that (-)methamphetamine, the parent compound of (-)deprenyl and (-)1-phenyl-2-propylaminopentane (PPAP), a deprenyl analogue free of MAO-B inhibitory potency but otherwise possessing the same pharmacological profile as (-)deprenyl, act similarly, furnishing direct evidence that enhancement of catecholaminergic activity in the brain by multiple, small dose administration of (-)deprenyl is unrelated to MAO-B inhibition.

Multiple, small dose administration of (-)deprenyl enhances catecholaminergic activity and diminishes serotoninergic activity in the brain and these effects are unrelated to MAO-B inhibition.

As a measure of the basic activity of the catecholaminergic and serotoninergic systems, the biogenic amines released from freshly excised brain tissue were measured by means of HPLC with electrochemical detection. Rats of both sexes were injected subcutaneously, daily for 21 days, either with saline or with a dose of one of the enantiomers of the following compounds: deprenyl; p-fluorodeprenyl; 1-phenyl-2-propylaminopentane, a deprenyl analogue free of MAO-B inhibitory potency; methamphetamine, the parent compound of deprenyl; and amphetamine, the parent compound of 1-phenyl-2-propylaminopentane. The release of the biogenic amines from brain tissue was measured 24 hours after the last injection. The effect of the two enantiomers of deprenyl was studied in five doses (0.01, 0.025, 0.05, 0.1 and 0.25 mg/kg), that of (-)1-phenyl-2-propylaminopentane in two doses (0.05 and 0.1 mg/kg), others in 0.05 mg/kg. Treatment with (-)deprenyl enhanced the release of dopamine from striatum, substantia nigra and tuberculum olfactorium (significant in 0.01-0.25 mg/kg) and the release of noradrenaline from the locus coeruleus (significant in 0.05-0.25 mg/kg), whilst the release of serotonin from the raphe was diminished (significant in 0.05-0.25 mg/kg in males and 0.25 mg/kg in females). (+)Deprenyl was slightly less potent than (-)deprenyl. Both p-fluorodeprenyl and 1-phenyl-2-propylaminopentane acted like deprenyl; the (+)enantiomers were more active than the (-)forms. (-)Methamphetamine was as potent as (-)deprenyl in enhancing the catecholaminergic activity and more potent than (-)deprenyl in diminishing the serotoninergic activity. (+)Methamphetamine was substantially less potent than (-)methamphetamine. (-)Amphetamine was as potent as (-)methamphetamine and (+)amphetamine was more potent than (+)methamphetamine in enhancing the catecholaminergic activity but neither (-)amphetamine nor (+)amphetamine diminished the serotoninergic activity. On the one hand, the results prove that the described effects of deprenyl are unrelated to MAO-B inhibition, on the other hand, they indicate the existence of hitherto unknown catecholaminergic and serotoninergic activity enhancer mechanisms in the brain, of which the former is stimulated and the latter inhibited by multiple, small dose administrations of deprenyl and related substances.

Sexually low performing male rats die earlier than their high performing peers and (-)deprenyl treatment eliminates this difference.

Out of 1600 sexually inexperienced 28-week old Wistar-Logan male rats 94 sexually inactive ('low performing', LP) and 99 highly active ('high performing', HP) rats were selected. The rats were treated from the 8th month of their life three times a week, subcutaneously, with either 0.9% NaCl or 0.25 mg/kg (-)deprenyl until they died. Their copulatory activity was tested once a week and their learning performance was measured in the shuttle box once in three months. The salt treated LP rats (n = 44) never displayed ejaculation during their life time, they were extremely dull in the shuttle box and lived 134.58 +/- 2.29 weeks. Their (-)deprenyl-treated peers (n = 48) became sexually active, their mating performance was substantially increased and lived 152.54 +/- 1.36 weeks, significantly longer than their salt-treated peers and as long as the salt-treated HP rats. The salt treated HP rats (n = 49) displayed 14.04 +/- 0.56 ejaculations during the first 36-week testing period and due to aging they produced 2.47 +/- 0.23 ejaculations between the 73-108th week of testing. Their learning performance was high. They displayed 78.45 +/- 3.01 conditioned avoidance responses (CAR) during the first 36-week testing period and this dropped to 50.67 +/- 2.99 (p < 0.01) during the 73-108th week of testing. They lived 151.24 +/- 1.36 weeks, significantly (p < 0.001) longer than their LP peers. The (-)depre-nyl-treated HP rats (n = 50) were sexually much more active than their salt-treated peers. They displayed 30.04 +/- 0.85 ejaculations during the first 36-week testing period and 7.40 +/- 0.32 ejaculations between the 73-108th week of testing. Also their learning performance was substantially increased. They produced 113.98 +/- 3.23 CARs during the first 36-week-testing period and 81.68 +/- 2.14 CARs during the 73-108th week of testing. They lived 185.30 +/- 1.96 weeks, significantly more than their salt-treated peers and out of the 50 rats 17 lived longer than the estimated technical life span (TLS).