Twin drug design, synthesis and evaluation of diosgenin derivatives as multitargeted agents for the treatment of vascular dementia

A novel series of multitargeted molecules were designed and synthesized by combining the pharmacological role of cholinesterase inhibitor and antioxidant of steroid as potential ligands for the treatment of Vascular Dementia (VD). The oxygen-glucose deprivation (OGD) model was used to evaluate these molecules, among which the most potent compound ML5 showed the highest activity. Firstly, ML5 showed appropriate inhibition of cholinesterases (ChEs) at orally 15 mg/kg in vivo. The further test revealed that ML5 promoted the nuclear translocation of Nrf2. Furthermore, ML5 has significant neuroprotective effect in vivo model of bilateral common carotid artery occlusion (BCCAO), significantly increasing the expression of Nrf2 protein in the cerebral cortex. In the molecular docking research, we predicted the ML5 combined with hAChE and Keap1. Finally, compound ML5 displayed normal oral absorption and it was nontoxic at 500 mg/kg, po, dose. We can draw the conclusion that ML5 could be considered as a new potential compound for VD treatment.

Rational Design and Multibiological Profiling of Novel Donepezil-Trolox Hybrids against Alzheimer's Disease, with Cholinergic, Antioxidant, Neuroprotective, and Cognition Enhancing Properties

A novel series of donepezil-trolox hybrids were designed, synthesized, and evaluated as multifunctional ligands against Alzheimer's disease (AD). Biological assays showed that these derivatives possessed moderate to good inhibitory activities against acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B) as well as remarkable antioxidant effects. The optimal compound 6d exhibited balanced functions with good inhibition against hAChE (IC₅₀ = 0.54 μM) and hMAO-B (IC₅₀ = 4.3 μM), significant antioxidant activity (41.33 μM IC₅₀ by DPPH method, 1.72 and 1.79 trolox equivalent by ABTS and ORAC methods), excellent copper chelation, and Aβ_1-42 aggregation inhibition effect. Furthermore, cellular tests indicated that 6d has very low toxicity and is capable of combating oxidative toxin (H₂O₂, rotenone, and oligomycin-A) induced neurotoxicity. Most importantly, oral administration of 6d demonstrated notable improvements on cognition and spatial memory against scopolamine-induced acute memory deficit as well as d-galactose (d-gal) and AlCl₃ induced chronic oxidative stress in a mouse model without acute toxicity and hepatotoxicity. In summary, both in vitro and in vivo results suggested that 6d is a valuable candidate for the development of a safe and effective anti-Alzheimer's drug.

Combined therapy with m-TOR-dependent and -independent autophagy inducers causes neurotoxicity in a mouse model of Machado-Joseph disease

A major pathological hallmark in several neurodegenerative disorders, like polyglutamine disorders (polyQ), including Machado-Joseph disease (MJD), is the formation of protein aggregates. MJD is caused by a CAG repeat expansion in the ATXN3 gene, resulting in an abnormal protein, which is prone to misfolding and forms cytoplasmic and nuclear aggregates within neurons, ultimately inducing neurodegeneration. Treatment of proteinopathies with drugs that up-regulate autophagy has shown promising results in models of polyQ diseases. Temsirolimus (CCI-779) inhibits the mammalian target of rapamycin (m-TOR), while lithium chloride (LiCl) acts by inhibiting inositol monophosphatase, both being able to induce autophagy. We have previously shown that chronic treatment with LiCl (10.4 mg/kg) had limited effects in a transgenic MJD mouse model. Also, others have shown that CCI-779 had mild positive effects in a different mouse model of the disease. It has been suggested that the combination of mTOR-dependent and -independent autophagy inducers could be a more effective therapeutic approach. To further explore this avenue toward therapy, we treated CMVMJD135 transgenic mice with a conjugation of CCI-779 and LiCl, both at concentrations known to induce autophagy and not to be toxic. Surprisingly, this combined treatment proved to be deleterious to both wild-type (wt) and transgenic animals, failing to rescue their neurological symptoms and actually exerting neurotoxic effects. These results highlight the possible dangers of manipulating autophagy in the nervous system and suggest that a better understanding of the potential disruption in the autophagy pathway in MJD is required before successful long-term autophagy modulating therapies can be developed.

Preclinical evaluation of Trichilia catigua extracts on the central nervous system of mice

ETHNOPHARMACOLOGICAL RELEVANCE

Trichilia catigua preparations have been popularly used in Brazil as a tonic for the treatment of fatigue, stress, impotence, and deficiency of memory. The aim of the present study was to investigate the possible antidepressant, anxiolytic, motor and cognitive effects of the crude extract (CE) or ethyl-acetate fraction (EAF) of Trichilia catigua. Analyses of the total phenolics and total tannins content, as well as the in vitro antioxidant activity of CE and EAF were also performed.

MATERIALS AND METHODS

CE (200-800 mg/kg) and EAF (100-400mg/kg) were orally administered to mice and 1h later the behavioral tests were performed. The free radical scavenging activity was measured by using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) method.

RESULTS

Single administration of CE (200-400 mg/kg) or EAF (100-400 mg/kg) did not change the behavior of the animals submitted to the elevated plus maze or their locomotor activity in the open field test. An antidepressant-like effect was detected with EAF (400 mg/kg) after acute administration. Both CE (800 mg/kg) and EAF (200 and 400 mg/kg), improve memory in mice as measured by an increased latency in the step-down inhibitory avoidance test. The EAF presented higher total phenolics and total tannins as compared to CE as well as it exhibited the best antioxidant activity.

CONCLUSIONS

The present results showed an in vitro antioxidant activity for EAF and suggested that it may be useful for cognitive improvement. It is possible that both functional and chemical activities are related.

BDNF regulates BIM expression levels in 3-nitropropionic acid-treated cortical neurons

3-Nitropropionic acid (3-NP) is an irreversible inhibitor of succinate dehydrogenase that has been used to explore the primary mechanisms of cell death associated with mitochondrial dysfunction and neurodegeneration in Huntington's disease. In this study we investigated the ability of brain-derived neurotrophic factor (BDNF) to suppress mitochondrial-dependent cell death induced by 3-NP in primary cortical neurons. This neurotrophin prevented 3-NP-induced release of cytochrome c and Smac/Diablo, caspase-3-like activity and nuclear condensation/fragmentation. Furthermore, it greatly increased phosphorylation of Akt and MAPK, suggesting the involvement of these signalling pathways in BDNF neuroprotection. Interestingly, BDNF decreased the levels of the pro-apoptotic protein Bim in mitochondrial and total cell lysates through the activation of the MEK1/2 pathway. This effect was due to an increase in the degradation rates of Bim. Our data support an important role for BDNF, in protecting cortical neurons against apoptotic cell death caused by inhibition of mitochondrial complex II.

Electrophysiological recording of re-aggregating brain cell cultures on multi-electrode arrays to detect acute neurotoxic effects

Neurotoxicity aims to understand how xenobiotics interfere with the function of the nervous system and to unravel their mechanisms of action. Neuronal activity is the primary functional output of the nervous system and deviations from its resting level may indicate toxicity. Consequently, the monitoring of electrophysiological activity in complex cell culture systems appears particularly promising for neurotoxicity assessment. To detect acute neurotoxic effects of chemicals we developed a test system based on the electrophysiological recordings from neural networks in re-aggregating brain cell cultures using multi-electrode arrays. We characterised the electrophysiological properties of the cultures and, using known neurotoxicants, evaluated their usefulness to predict neurotoxic effects. Aggregates displayed evoked field potentials and spontaneous neural activity involving glutamatergic and GABAergic synaptic transmission. Paired pulse inhibition indicated the presence of short-term synaptic plasticity via functional inhibitory networks. Cultures were treated with 0.1-100 microM of trimethyltin chloride (TMT), methyl mercury chloride (MeHgCl), parathion or paraoxon, and with 0.1-100mM of ethanol for up to 100 min. TMT (10 microM), MeHgCl (1 microM) and ethanol (100mM) all decreased the amplitude of evoked field potential. The effect of ethanol was reversible. In contrast paraoxon (10 microM) increased the amplitudes of evoked field potentials while parathion showed no significant effects. The effects of TMT and ethanol on the frequency of spontaneous activity were consistent with those obtained for evoked field potentials. All effects occurred at levels at which cytotoxic injuries were not detectable. Taken together our system expressed electrophysiological properties similar to those of established slice culture preparations. It detected known neurotoxicants at subcytotoxic levels and therefore appears suitable for the assessment of toxic insults specifically interfering with nervous system function, e.g. neuronal activity, synaptic transmission and short-term plasticity. If incorporated into testing strategies, it might represent a valuable tool for the mechanistic assessment of neurotoxic effects.

Pharmacological actions of Thespesia populnea relevant to Alzheimer's disease

Thespesia populnea (Malvaceae) is a large tree found in the tropical regions and coastal forests of India. Various parts of T. populnea are found to possess useful medicinal properties, such as antifertility, antibacterial, anti-inflammatory, antioxidant, purgative and hepatoprotective activity. The present study was undertaken to investigate the effects of T. populnea bark on cognitive functions, total cholesterol levels and cholinesterase activity in mice. A total of 312 mice divided into 52 different groups were employed in the present investigation. The ethanolic extract of T. populnea (TPE) was administered orally in three doses (100, 200 and 400 mg/kg) for 7 successive days to different groups of young and aged mice. The learning and memory parameters were assessed using elevated plus maze and passive avoidance apparatus. TPE (200 and 400 mg/kg, p.o.) showed significant improvement in memory of young and aged mice. TPE also reversed the amnesia induced by scopolamine (0.4 mg/kg, i.p.) and diazepam (1 mg/kg, i.p.). Furthermore, TPE reduced significantly the central (brain) cholinesterase activity in mice. TPE exhibited a remarkable cholesterol lowering property comparable to simvastatin (a standard drug) in the present study. Furthermore, we observed that, T. populnea bark possessed a powerful memory enhancing activity in mice. Since diminished cholinergic transmission and increased cholesterol levels appear to be responsible for development of amyloid plaques and dementia in Alzheimer patients, TPE may prove to be a useful medicine on account of its multifarious beneficial effects, such as memory improving property, cholesterol lowering, anticholinesterase and anti-inflammatory activity. Therefore, T. populnea bark appears to be a promising candidate for improving memory and it would be worthwhile to explore the potential of this plant in the management of Alzheimer patients.

The combined use of human neural and liver cell lines and mouse hepatocytes improves the predictability of the neurotoxicity of selected drugs

The cytotoxicity of amitriptyline (0-100microM), selegiline (0-4.5microM), carbamazepine (0-420microM) and paracetamol (0-10mM) was studied in metabolically competent mouse hepatocytes, metabolically incompetent human hepatoblastoma (HepG2) cells, and in neuroblastoma (SH-SY5Y) and astrocytoma (U-373 MG) cells, by using luminescence-based ATP measurement as an endpoint of cell toxicity. The aim was to evaluate the potential of the selected cell cultures to recognize metabolism-induced toxicity of the test compounds, and to predict further hepatic and neural toxicity. In SH-SY5Y cells amitriptyline was severely toxic, while selegiline and paracetamol failed to show any toxic effect, and carbamazepine was only slightly toxic at the highest concentration. In U-373 MG cells the onset of amitriptyline toxicity started earlier than in SH-SY5Y cells. However, the highest amitriptyline concentration resulted in approximately 100% decrease in the viability of the SH-SY5Y cells, whereas the decrease in the viability of the U-373 MG cells was only approximately 30%. Selegiline, carbamazepine and paracetamol were toxic in mouse hepatocytes (but not in HepG2 cells), which suggests that these drugs may show metabolism-dependent (neuro)toxicity. In conclusion, compared to the use of neurons alone, better estimations of neurotoxicity can be made by the combined use of metabolically competent hepatocytes and glial cells (e.g. U-373 MG) together with neuronal cells (e.g. SH-SY5Y).

Calbindin D-28 and microtubule-associated protein-2: their use as sensitive immunohistochemical markers of cerebellar neurotoxicity in a regulatory toxicity study

The aim of this study was to develop an immunohistochemical (IHC) method for calbindin D-28 (CB-28) and microtubule-associated protein-2 (MAP-2) and evaluate their expression as markers in the detection, characterisation and grading of unexpected cerebellar toxicity in the rat. High power examination of H&E-stained brain sections of treated rats 2 days following a single oral dose of a novel compound revealed irregular vacuolation of the molecular layer and Purkinje cell degeneration. Animals killed after 14 days recovery showed Purkinje cell degeneration but vacuolation of the molecular layer was absent. In control animals, CB-28 and MAP-2 expression was high in Purkinje cell dendrites and cell bodies in the molecular layer. In treated animals, low power examination revealed loss of CB-28 and MAP-2 expression in degenerating neurons arranged in parasagittal stripes within the vermis. This is the first description of successful use of these two markers in a regulatory toxicity study using FFPE brain. In particular, CB-28 provides a sensitive method for characterising CNS toxicity which can be detected at low power enabling easier detection, screening and grading of neurotoxicity.

Human cord blood-derived neural stem cell line—Possible implementation in studying neurotoxicity

Neural stem cell line developed from human umbilical cord blood (HUCB-NSC) [Buzańska et al., 2003. Journal of Neurochemistry 85, 33] is an ethically uncontroversial source of stem cells, able to differentiate into neuronal, astrocytic and oligodendroglial lineages. Developmental fate decisions of HUCB-NSC can be experimentally manipulated in vitro by the presence of trophic factors, mitogenes and neuromorphogenes, but can also be influenced by neurotoxins. In this report two-dimensional (2-D) and three-dimensional (3-D) HUCB-NSC cultures are introduced as useful models for testing developmental neurotoxicity. For 2-D culture models we established a standardized method for the assessment of the growth rate and cell differentiation in 96-well plates. The proliferative capacity of the HUCB-NSC was monitored by the MTT test while their ability to differentiate into neural-like cells by immunocytochemistry of beta-tubulin III and MAP-2 for neurons, GFAP and S-100beta for astrocytes and GalC for oligodendrocytes. The 3-D culture of HUCB-NSC is represented by neurospheres. Proliferation and migration of the intermediate precursors from attached neurospheres are shown to be controlled and altered by various growth factors and further modulated by the extracellular matrix component-fibronectin. Thus, neurospheres derived from the HUCB-NSC line can represent a suitable model of the activation of dormant stem cells residing in their niche, and can be used for neurotoxic studies.

CNS activities of Celesia coromandeliane Vahl. in mice

The dried extracts of aerial parts of Celesia coromandeliane Vahl. (Scrophulariaceae) were evaluated for CNS activities in mice. The methanol extract of aerial part of Celesia coromandeliane (MECC) was found to cause significant depression in general as well as exploratory behavioral profiles in mice. MECC showed reduction in muscle relaxant activity by 30 degrees inclined screen test, as well as potential remarkably the pentobarbitone sodium-, diazepam- and meprobamate-induced sleeping time of mice. The petroleum ether extract of aerial parts of Celesia coromandeliane (PECC) showed significant analgesic properties as evidenced by the significant reduction in the number of writhes and stretches induced in mice by 1.2% acetic acid solution. Pretreatment with PECC caused significant protection against strychnine- and leptazol-induced convulsions. All these results were compared with respective controls for the evaluation of significance. The presence of steroids in PECC and saponins in MECC might be responsible for respective CNS activities in mice.

Spectrum of effects detected in the rat functional observational battery following oral administration of non-CNS targeted compounds

INTRODUCTION

The Functional Observational Battery (FOB) is a systematic evaluation of nervous system function in the rat, comprising more than 30 parameters across autonomic, neuromuscular, sensorimotor and behavioural domains. We have collated FOB outcomes from 50 compounds that were not targeted at CNS disorders, and would therefore be anticipated to have relatively few CNS side-effects, for evaluation of the FOB as part of the safety pharmacology 'core battery'.

METHODS

Male Han Wistar rats (200-300 g) were used, with n=6 per treatment group. Each compound was tested acutely at 3 dose levels (oral route), from the therapeutic dose up to either 100 times this dose or to the maximal tolerated dose (MTD). A vehicle control group was included in each study.

RESULTS

Effects were detected in the FOB for 94% of compounds tested. The commonest effects were weight loss/decreased body weight gain overnight post-dose (46% of compounds), and changes in core temperature (36%). Dose-related effects were observed with 62% of compounds; the commonest was decreased body weight gain (32%), followed by effects on tail flick latency (14%), landing foot splay (12%), decreased rectal temperature (10%), time to exit the centre circle in the open field (10%), diarrhoea/loose faeces (8%), respiratory effects (4%), grasping reflex (4%) and supported rears in the open field (4%). Remaining parameters were affected by < or =2% of compounds.

DISCUSSION

The value of doing the FOB as part of the safety pharmacology 'core battery' is emphasised by the fact that, even for non-CNS targeted compounds, the majority affected at least one of the parameters in the FOB. These data may also help to anticipate the most frequently required 'follow-up' studies.

Synthesis and biological activity of new derivatives of 3-phenoxymethyl-4-R-D2-1,2,4-triazoline-5-thione

New derivatives of 1,2,4-triazoline-5-thione system were obtained. The effects of both these compounds AP-I (3-phenoxymethyl-4-phenyl-D2-1,2,4-triazoline-5-thione) and AP-II (3-phenoxymethyl-4-ethyl-D2-1,2,4-triazoline-5-thione) on the central nervous system (CNS) of mice were studied.

The influence of some aminoalkanolic xanthone derivatives on central nervous and cardiovascular systems in rodents

A series of appropriate aminoalkanolic derivatives 2- or 4-methylxanthone was synthesized and evaluated for anticonvulsant activity in the maximal electroshock seizure (MES) and subcutaneous pentylenetetrazole seizure threshold (scPtz) assays, and for neurotoxicity (TOX). The most interesting result was the anticonvulsant activity of (R,S)-2N-(6-chloro-2-xanthonemethyl-2N-methylamino-1-propanol hydrochloride (II, which displayed anti-MES and anti-scPtz activity. Some of the obtained compounds (I - IV and V - VII) were also tested for their effect on the circulatory system (the effect on normal electrocardiogram, protection against adrenaline-, barium-, calcium- and/or strophanthine-induced arrhythmias, the effect on the arterial blood pressure and respiratory movements) and acute toxicity.

Investigation of testicular toxicity of nefiracetam, a neurotransmission enhancer, in rats

Testicular toxicity of nefiracetam (N-(2,6-dimethylphenyl)-2-(2-oxo-1-pyrrolidinyl) acetamide), a neurotransmission enhancer, was investigated in male Slc:SD rats. Nefiracetam was orally administered daily at 1500 mg/kg for 4 weeks, and the animals were killed sequentially during the course of administration to determine testicular histopathological changes and sperm head counts (SHC), and hormonal changes. Retention of step 19 spermatids, sporadic degeneration of pachytene spermatocytes and step 7 spermatids in the stage VII seminiferous tubules, and a decrease in SHC were seen as earliest changes after 1 week of administration. These changes gradually advanced up to atrophy of seminiferous tubules with multinucleated-giant-cell formation after 4-week administration. Serum and testicular testosterone levels were decreased, but recovered to the control levels within a day following a single administration, and the decreases were repeated after 1-week administration. These results suggest that nefiracetam-induced earliest changes could be caused by the decreased level of testicular testosterone.

Sensorimotor deficits and increased brain nicotinic acetylcholine receptors following exposure to chlorpyrifos and/or nicotine in rats

Despite well-known adverse effects associated with cigarette smoking, approximately 20% of the US population continues to smoke and many more are exposed to environmental tobacco smoke. Many of the same individuals are also exposed to environmental neurotoxic chemicals such as the organophosphorus insecticide chlorpyrifos. In the present study, the effects of exposure to low doses of nicotine and chlorpyrifos alone and in combination, were studied on the central cholinergic system and sensorimotor performance in rats. Male Sprague-Dawley rats (250-300 g) were treated with nicotine (1 mg/kg s.c., in normal saline), chlorpyrifos (0.1 mg/kg dermally, in 0.1 ml 70% ethanol), or a combination of both, daily for 30 days. Control rats were treated with saline and dermally with ethanol. Sensorimotor behavior was evaluated 24 h following the last dose using a battery of tests. There was a significant deficit in incline plane performance, beam-walk score and beam-walk time following exposure to each chemical, alone or in combination. The deficit in incline plane performance was greater when the two chemicals were given in combination than with either compound alone. Biochemical analysis showed a decrease in cerebellar and an increase in midbrain acetylcholinesterase (AChE) activity following combined exposure. Exposure to nicotine alone resulted in a significant increase in AChE activity in brainstem and midbrain, whereas there was no significant change after exposure to chlorpyrifos, alone. A significant increase in ligand binding to nicotinic acetylcholine receptors (nAChR) was observed in brainstem and cortex following exposure to nicotine or chlorpyrifos. This was further augmented with combined exposure, which caused a modest but significant increase in m2 muscarinic acetylcholine receptors (m2-mAChR) ligand binding in the cortex. These data suggest that exposure to either nicotine or chlorpyrifos or a combination of the two may impair neurobehavioral performance and affect the central nervous system cholinergic pathways.

Synthesis and biological activity of certain novel derivatives of 1H-pyrrolo[1,2-c][1,3]thiazine

The reaction of 2-(beta-hydroxyethyl)-pyrrolidine with isothiocyanates gave rise to the formation of thiourea derivatives which cyclised on refluxing in hydrobromic acid to yield N-(3,4,4a,5,6,7-hexahydro-1H-pyrrolo[1,2-c][1,3]thiazin-1-ylidene)-aryl(alkyl)amines. The results of preliminary pharmacological screening are presented.

Synthesis and preliminary screening of derivatives of 2-(4-arylpiperazin-1-ylalkyl)-3-oxoisothiazolo[5,4-b] pyridines as CNS and antimycobacterial agents

We have synthesized several new isothiazolopyridines possessing a side chain at the isothiazole ring typical, among others, for trazodone or NAN-195. Representatives of the novel isothiazolopyridines were examined for acute toxicity and in several commonly used CNS tests in mice and for arterial blood pressure in rats. Three of the five compounds tested showed significant analgesic activity. The most active compound (3b) exhibited analgesic action in the "writhing" test in a dose 1/1280 of LD50 (LD50 = 1135.5 mg/kg) after administration i.p. to mice. Additionally, the compounds described here and related isothiazolopyridines obtained previously were evaluated against Mycobacterium tuberculosis H37Rv at 12.5 micrograms/ml in in vitro assays. Seven of the nineteen compounds tested showed 100% inhibition of that mycobacterium.

Synthesis and biological activity of BIS-1,2,4-triazole and BIS-1,3,4-thiadiazole derivatives

Synthesis of some new 1,2,4-triazole and 1,3,4-thiadiazole derivatives via the condensation of N'-substituted amidrazones and p-phenylenediisothiocyanate (PPD) is presented. The reaction conditions are discussed. Results of a preliminary pharmacological screening are presented.

Distinct features of seizures induced by cocaine and amphetamine analogs

Seizure-related emergencies caused by stimulants of abuse have been increasing. To better understand the nature of these drug-induced convulsions, we characterized the seizure patterns associated with high doses of cocaine, and the amphetamine analogs, methamphetamine, methylenedioxymethamphetamine (MDMA) and 4-methylaminorex. The features of the stimulant-induced seizures were distinct and included the following: (1) the duration of convulsive activity was shortest for cocaine and longest for methamphetamine, (2) only MDMA produced a secondary clonic phase after the initial ictal event, and (3) 4-methylaminorex manifested a very steep dose-response curve. Differential preventive profiles of anticonvulsant agents on the stimulant-induced seizures also were observed. For example, cocaine-related seizures were most effectively prevented by, while methamphetamine-induced seizures were completely refractory to, phenytoin pretreatment. The only anticonvulsants which appeared to influence methamphetamine-related convulsions were diazepam and valproate. A unique feature of 4-methylaminorex was that related seizures were almost completely blocked by the calcium channel blocker, flunarizine.

CNS effects of a series of 1,2,4-triazolyl heterocarboxylic derivatives

A series of 1,2,4-triazolyl heterocarboxylic derivatives were tested for acute toxicity and CNS effects in mice. Several of these compounds demonstrated clear psychostimulant effects. Other components of the series, however, showed a definite central depressant activity. Some of the screened derivatives showed interesting anxiolytic properties.

Synthesis and pharmacological screening of pyrazolo[3,4-c]pyridazine derivatives

Ethyl 3-chloro-6-(4-chlorophenyl)-pyridazine-4-carboxylate [VII] was cyclized with some nucleophilic reagents (hydrazine hydrate or N-monosubstituted hydrazines) to the new derivatives of pyrazolo[3,4-c]pyridazine [IXa-d]. The structures of the novel compounds were confirmed by elemental and spectral analyses. The effect of several synthesized derivatives on the central nervous system was studied.

Synthesis, structures and biological activity of some 4-amino-3-cinnoline-carboxylic acid derivatives. Part 3: 1,3-Oxazino[5,4-c]cinnolines and pyrimido[5,4-c]cinnolines

6,7,8-Substituted 4-amino-3-cinnolinecarboxylic acids 1 were condensed with acid anhydrides to corresponding 1,3-oxazino[5,4-c]cinnolines 2. The reactions of 1,3-oxazino[5,4-c]cinnolines 2 with amines, hydrazine, hydroxylamine, alanine ethyl ester provided pyrimido[5,4-c]cinnolines 3, 4. Selected 3-substituted 2-methylpyrimido[5,4-c]cinnolin-4(3 H)-ones have been screened for CNS activity.

Synthesis of N-benzyl-4-oxo-1,2,3,4-tetrahydrocinnolines

The method of preparation of N1 and N2-substituted 4-hydroxycinnolines by alkylation with benzyl bromide of the corresponding 4-hydroxycinnolines is described. The obtained derivatives were reduced to the corresponding N-benzyl-4-oxo-1,2,3,4-tetrahydrocinnolines. The effect of some synthesized derivatives on central nervous system was studied.

Quantification of the hindlimb extensor thrust response in rats

This report describes a procedure for measuring the extensor thrust response (ETR) and summarizes the results of initial validation experiments using adult Long-Evans rats. The ETR can be quickly elicited and the force measured by pressing against the hindlimb footpads with a small rectangular plate or bar attached to a digital force gauge. Output of the force gauge is analyzed and displayed with commercially available hardware and software. The first experiment compared the acute effects of i.p. injection of chlorpromazine (CPZ; 1, 4, or 7 mg/kg) or amphetamine (AMP; 0.3, 1, or 3 mg/kg) on the ETR and forelimb/hindlimb grip strength (FL/HL-GS) in male and female rats. CPZ decreased both ETR and FL/HL-GS values. Both 1 and 3 mg/kg AMP increased grip strength values but decreased ETR values. A second experiment compared the evolution of changes in ETR, FL/HL-GS, and peripheral neurophysiological measures during 8 weeks of daily oral dosing of 10 mg/kg acrylamide (ACR) monomer. ACR-treated rats exhibited a progressive decrease in ETR beginning after 3 weeks of dosing, whereas a reduction of HL-GS was observed beginning much later, after 7 weeks of dosing. The deficit in ETR progressed in the absence of any changes in spontaneous or evoked electrophysiological abnormalities in neuromuscular function, but was accompanied by a decrease in peripheral nerve conduction velocity. Taken together, the results indicate that the ETR can be used to characterize functional effects in both single dose and repeated dose experiments. The data also indicate that the ETR does not merely duplicate the information provided by FL/HL-GS, and suggest a hypothesis that the ETR may be sensitive to neurotoxicant-induced changes in somatosensory function.

Synthesis, structures and biological activity of some 4-amino-3-cinnolinecarboxylic acid derivatives. Part 2

6,7,8-Substituted 4-amino-3-cinnolinecarboxylic acids 1 were condensed with amines to the corresponding 4-amino-3-cinnolinecarboxamides 7, 8. A variety of pharmacological tests showed a significant CNS activity of some new amides. Decarboxylation of 4-amino-3-cinnolinecarboxylic acids 1 yielded the corresponding 4-aminocinnolines 4 and alkaline hydrolysis of 1 gave 4-oxo-3-cinnolinecarboxylic acids 2. The acids 1 were converted into pyrimido[5,4-c]cinnolines 6 on two ways of synthesis.

Influence of common drugs and related factors on stroke outcome

Laboratory studies show that recovery after brain injury can be influenced by drugs that affect certain central neurotransmitters. The effects of these drugs may be either beneficial or harmful. Although issues related to drug dose, the timing of interventions relative to the deficit, and the nature of concomitant experience or training may be critical, preliminary clinical studies suggest that similar drug effects may occur in humans recovering from stroke. Recognition of these data is important because many of the drugs that may impair recovery are commonly prescribed to stroke patients for the treatment of coincident medical conditions and should be avoided if possible. Pharmacotherapy to enhance recovery may be possible in the future.

Pharmacological and histopathological aspects of 1-methyl-4-phenyl-4-hydroxy-piperidine (MPIP)

Increasing dosages of 1-methyl-4-phenyl-4-hydroxypiperidine (MPIP) were administered i.p. to rats. Histopathological examination of these animals revealed effects on the central nervous system.

Chemical and pharmacological properties of new tetrahydropyrimido-[2,1-f]-purines

Following a research program on piperazinoalkyl-substituted tricyclic purines, a number of N-9-aryl(alkyl)-piperazinopropyl substituted tetrahydropyrimido-[2,1-f]-purines were synthesized and tested pharmacologically with respect to their influence on the central nervous system. Two of the new compounds induced hypothermia and decreased the spontaneous locomotor activity of mice.

Are interspecies comparisons in the toxicity of centrally acting drugs valid without brain concentrations? A commentary

Many pharmacological and toxicological studies of centrally acting drugs are undertaken in animals at doses expressed in mg.kg-1, and the results extrapolated to the clinical dose in man. Safety margins based on such no or lowest effect levels may have little relevance since they do not take into account differences in the kinetics and metabolism of the compounds. These deviations are accentuated when extremely high doses are used, and saturation of metabolism occurs.

Quantitative aspects of drug and toxicant-induced astrogliosis

A universal cellular reaction to damage of the CNS is hypertrophy of astrocytes. The hallmark of this response, often termed 'reactive gliosis', is the enhanced expression of the major intermediate filament protein of astrocytes, glial fibrillary acidic protein (GFAP). This latter observation suggests that increased synthesis of GFAP would occur in response to diverse neurotoxic insults. To investigate this possibility, prototype neurotoxicants were administered to experimental animals and the effects of these agents on the tissue content of GFAP was determined by immunoassay. Assays of GFAP were found to reveal dose-, time- and region-dependent patterns of neurotoxicity at toxicant dosages below those that cause light microscopic evidence of cell loss or damage. Moreover, the temporal and regional increments in GFAP correspond to the temporal and regional patterns of argyrophilia, as revealed by the cupric silver degeneration stain of de Olmos. Our findings indicate that assays of GFAP represent a sensitive, simple and quantitative approach for evaluation of nervous system damage. Combining this indirect yet quantitative indicator of neurotoxicity with more traditional neuroanatomical endpoints, should augment the armamentarium of techniques useful for detection and characterization of neurotoxicity.

Synthesis and action on the central nervous system of some N2-substituted cinnoline derivatives

Alkylation of 4-hydroxycinnolines using ethyl bromoacetate resulted in N2-substituted acetic acids. These acids were converted to esters and amides. Some of the obtained acids were reduced with zinc dust to give 4-oxo-1,2,3,4-tetrahydro-2-cinnolineacetic acids. Several of the compounds were tested for their effect on central nervous system.

Relevance of drug-melanin interactions to ocular pharmacology and toxicology

In melanocytes, the biosynthesis of L-dopa derived indole polymer, melanin, is accelerated by tyrosinase and related enzymes. The brown to black pigment is characterized by a stable free-radical property. In humans, a pigment dependent slow onset of ocular actions of ephedrine, atropine, cocaine, pilocarpine and related medications was observed. Extensive accumulation of drugs by melanin appears to be the most important factor governing the long term therapeutic/toxicological activities. Drugs crossing placental circulation are localized in the mouse fetal eye. Thus, drugs exhibit a high binding capacity for melanin containing tissues. Studies on synthetic melanin and melanin granules also indicated a high binding capacity of many therapeutic classes of drugs, including psychotropics. In addition to the liposoluble property of the molecule, there is a definite relationship between chemical structure and the affinity of drugs for melanin. For example, the affinity of chlorpromazine for melanin is higher than that of chlorprothixene. NMR studies, with soluble melanins indicate that there is a steric preference among ephedrine enantiomers. A high binding capacity indicates that more than two molecules of (-)-ephedrine may complex with one indole unit of melanin. Ocular drug development calls for the study of qualitative and quantitative aspects of drug-melanin interaction.

Synthesis and pharmacological properties of N-(4-substituted-1-piperazinylalkyl)-1-butyl-2,5-dimethylpyrrole-3,4- dicarboxyimide derivatives

The preparation of a number of N-(4-substituted-1-piperazinylalkyl)-1-butyl-2,5-dimethylpyrrol e-3,4- dicarboxyimides (3) is described. The structures of the novel compounds were confirmed by elemental and spectral analyses. The results of a preliminary pharmacological study of CNS effects caused by compounds 3 are reported.

Thiazolidinone congeners as central nervous system active agents

3-(Benzylidene amino)-2-imino-4-thiazolidinones (IIa-c) synthesized by cyclization of substituted thiosemicarbazones (Ia-c) were converted into 2-amino-3-(substituted benzylamino)-4-thiazolidinones (IIIa-c), 2-imino-3-(alpha-aryl azo benzylidene) amino-4-thiazolidinones (IVa-f) and 2-(2-amino-4-oxo-3-thiazolidinyl)-3-aryl-4-isothiazolidinones (VIa-c), IVa-f were finally converted into 5-(arylamino methyl)-2-imino-3-(alpha-aryl azobenzylidene)-amino-4-thiazolidinones (Va-l). These compounds III, V and VI were evaluated for their monoamine oxidase (MAO) inhibitory activity in vitro and various CNS activities in vivo. Some of the compounds exhibited promising CNS activity.

Synthesis and CNS activity of some new substituted indeno [1,2-c] pyrazoles

Some new 1-(6'-substituted-4'-methylquinol-2'-yl)-3-methyl-indeno[1,2- c]pyrazoles (Va-d) have been synthesized by the condensation of 2-acetylindane-1,3-dione (I) with 2-hydrazino-4-methyl-6-substituted quinolines (IIa-d), followed by cyclodehydration with polyphosphoric acid and Wolff-Kishner reduction. Compounds (IVa-d) showed noticeable CNS activity.

Synthesis and pharmacological evaluation of triazolo derivatives of 8-amino-10,11-dihydro-dibenzo[b,e]1,4-thiazepine-11-one

In the present communication, the syntheses, characterization and pharmacological evaluation of 8-amino-(1,2,4)-triazolo[4,3-d][b,e]1,4-dibenzothiazepine (4) and its various substituted analogs (6-9) are reported.

Synthesis of p-menthane derivatives with potential biological activity

The synthesis of amino ketones and amino alcohols in p-menthane series is presented. These compounds were obtained in Mannich reaction, starting from the unsaturated ketone p-mentha-6,8-dien-2-one and its saturated analogue p-menthan-2-one. The structures of the compounds obtained were established by means of chemical transformations and elemental and spectral (IR, 1H NMR) analysis. The compounds obtained were subjected to the pharmacological investigations.

Hydrophobicity and central nervous system agents: on the principle of minimal hydrophobicity in drug design

The problem of getting drugs across the so-called blood-brain barrier (BBB) has long been under extensive investigation; however, the other side of the problem, that of keeping drugs out of the central nervous system (CNS), has not been studied so intently. As we strive to make more and more refined drugs with fewer side effects, the problem of keeping drugs out of the CNS has possibly become more important than getting them in. The role of lipophilicity has long been recognized as being important in CNS penetration by chemicals, but we believe that not enough attention has been devoted to just exactly what is meant when it is said that "a lipophilic drug is needed for CNS penetration." How lipophilic? Can hydrophilic properties keep drugs out of the CNS? How hydrophilic should they be? There are other reasons for making drugs hydrophilic. Hydrophobic drugs, other factors being equal, are more inhibitory of biochemical systems than hydrophilic congeners. Evidence is beginning to show that cytochrome P450 is induced in direct proportion to hydrophobicity by a variety of compounds, and cytochrome P450 may produce modifications in lipophilic molecules in the body. Hydrophobic drugs are more slowly eliminated. This report discusses these problems in terms of the octanol-water (log P) hydrophobic scale. The principle is proposed that, without convincing evidence to the contrary, drugs should be made as hydrophilic as possible without loss of efficacy. Antihistamines are discussed in terms of what kind of hydrophobic-hydrophilic balance is best to avoid CNS-related problems.

Choline availability: effects on the toxicity of centrally active drugs

The effect of chronic choline supplementation was studied on the toxicity of various pharmacological agents in rats and mice. Choline prevented both the incidence of seizures and the consequent lethality of nicotine, paraoxon, pentylenetetrazol, and strychnine. Nicotine toxicity was most markedly affected, and the prophylactic effects of choline were present in both rats and mice following either dietary or parenteral supplementation. Results suggest that chronic choline availability may alter neuronal membrane excitability.

[Pharmacological activity and toxicity of neurotropic agents in experimental hypodynamia]

Comparison of ED50, the indices of pharmacological range, LD50, risk coefficients, the size of the area of toxic activity, maximal tolerated and absolute lethal doses showed in acute experiments on intact and "hypodynamic" mice that under conditions of a short-term tension-producing hypodynamia in the animals, the pharmacological activity of the test neurotropic agents exhibiting a central action changes, whereas their toxicity remains unchanged.

Heterocyclic tricycles as potential CNS agents I: 4-aminoalkylindeno[1,2-c]pyrazoles

Series of 4-(3-dimethylaminopropyl)-4-hydroxyindeno[1,2-c]pyrazoles and 4-(1-methyl-4-piperidyl)-4-hydroxyindeno[1,2-c-]pyrazoles were synthesized and identified. The compounds were evaluated as potential CNS agents using spontaneous and forced motor activity in mice as an initial test. 2-Ethyl-3-methyl-4-(1-methyl-4-piperidyl)-4-hydroxyindeno[1,2-c]pyrazole possessed significant biological activity.