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Plant-derived substances have regained interest in the fight against antibiotic resistance owing to their distinct antimicrobial mechanisms and multi-target properties. With the recent advances in instrumentation and analysis techniques, OMIC approaches are extensively used for target identification and elucidation of the mechanism of phytochemicals in drug discovery. In the current study, RNA sequencing based transcriptional profiling together with global differential protein expression analysis was used to comparatively elaborate the activities and the effects of the plant alkaloids boldine, bulbocapnine, and roemerine along with the well-known antimicrobial alkaloid berberine in Bacillus subtilis cells. The transcriptomic findings were validated by qPCR. Images from scanning electron microscope were obtained to visualize the effects on the whole-cells. The results showed that among the three selected alkaloids, only roemerine possessed antibacterial activity. Unlike berberine, which is susceptible to efflux through multidrug resistance pumps, roemerine accumulated in the cells. This in turn resulted in oxidative stress and building up of reactive oxygen species, which eventually deregulated various pathways such as iron uptake. Treatment with boldine or bulbocapnine slightly affected various metabolic pathways but has not changed the growth patterns at all.

5-hydroxytryptamine (5-HT) is a key regulator of muscle contraction in parasitic flatworms. In Schistosoma mansoni, the myoexcitatory action of 5-HT is effected through activation of a serotonergic GPCR (Sm.5HTRL), prioritizing pharmacological characterization of this target for anthelmintic drug discovery. Here, we have examined the effects of several aporphine alkaloids on the signaling activity of a heterologously expressed Sm.5HTRL construct using a cAMP biosensor assay. Four structurally related natural products – nuciferine, D-glaucine, boldine and bulbocapnine – were demonstrated to block Sm.5HTRL evoked cAMP generation with the potency of GPCR blockade correlating well with the ability of each drug to inhibit contractility of schistosomule larvae. Nuciferine was also effective at inhibiting both basal and 5-HT evoked motility of adult schistosomes. These data advance our understanding of structure-affinity relationships at Sm.5HTRL, and demonstrate the effectiveness of Sm.5HTRL antagonists as hypomotility-evoking drugs across different parasite life cycle stages., Graphical abstract, Highlights • Application of a cAMP biosensor to probe properties of a schistosome serotonergic GPCR. • Several aporphine alkaloid derivatives act as 5-HT receptor antagonists. • Potency of GPCR blockade correlates well with inhibition of schistosomule contractility. • The natural product nuciferine acts as an effective inhibitor of adult worm motility.

The cytochrome P450 2C19 (CYP2C19) enzyme plays an important role in the metabolism of many commonly used drugs. Relatively little is known about CYP2C19 inhibitors, including compounds of natural origin, which could inhibit CYP2C19, potentially causing clinically relevant metabolism-based drug interactions. We evaluated a series (N = 49) of structurally related plant isoquinoline alkaloids for their abilities to interact with CYP2C19 enzyme using in vitro and in silico methods. We examined several common active alkaloids found in herbal products such as apomorphine, berberine, noscapine, and papaverine, as well as the previously identified mechanism-based inactivators bulbocapnine, canadine, and protopine. The IC50 values of the alkaloids ranged from 0.11 to 210 µM, and 42 of the alkaloids were confirmed to be time-dependent inhibitors of CYP2C19. Molecular docking and three-dimensional quantitative structure-activity relationship analysis revealed key interactions of the potent inhibitors with the enzyme active site. We constructed a comparative molecular field analysis model that was able to predict the inhibitory potency of a series of independent test molecules. This study revealed that many of these isoquinoline alkaloids do have the potential to cause clinically relevant drug interactions. These results highlight the need for studying more profoundly the potential interactions between drugs and herbal products. When further refined, in silico methods can be useful in the high-throughput prediction of P450 inhibitory potential of pharmaceutical compounds.

Cissampelos capensis, commonly known by the Afrikaans name “dawidjies” or “dawidjieswortel”, is the most important and best known medicinal plant of the family Menispermaceae used by the Khoisan and other rural people in the western region of South Africa. The main alkaloids in the leaves, stems and rhizomes were isolated and identified. Several of the main compounds were previously found in species of the related genus Antizoma and this similarity indicates that the two genera are closely related if not congeneric. Bulbocapnine (an aporphine alkaloid), dicentrine (an aporphine alkaloid) and salutaridine (a morphinane alkaloid) were the main alkaloids in the leaves, while bulbocapnine, cissacapine, cycleanine and insularine (the last three are bisbenzyltetrahydro-isoquinoline alkaloids) are the major compounds in the stems. The rhizome contains mostly bisbenzyltetrahydroisoquinoline alkaloids, with 12-O-methylcurine, cissacapine and cycleanine as the main ones. Alkaloids appear to be quite variable within different plant parts and different provenances, as confirmed by the difference in alkaloid patterns between coastal and inland forms of Cissampelos capensis (the morphinane alkaloid salutaridine, for example, is the major leaf alkaloid along the coast but is practically absent from the inland form of the species). The variety of alkaloids identified may contribute to the medicinal value of this species. The data on alkaloidal variation in the species has potential value and practical applications in chemotaxonomy, toxicology and pharmacognosy.

The main alkaloids of Antizoma miersiana and one of two species of the southern African endemic genus Antizoma (Menispermaceae), have been studied for the first time. Eight isoquinoline alkaloids could be positively identified (structural type in brackets): crotsparine (proaporphine); bulbocapnine and dicentrine (aporphine); cissacapine, cycleaneonine, cycleanine, insulanoline and insularine (bisbenzyltetrahydroisoquinoline). Crotsparine and bulbocapnine were the main alkaloids in the leaves, while bulbocapnine, dicentrine, insulanoline and an unidentified alkaloid are the major compounds in stems. The rhizome contains small amounts of all except crotsparine. There are clear differences, not only between various plant parts, but also between the two species of Antizoma. Bulbocapnine, for example, was previously found to be absent from the leaves and stems of Antizoma angustifolia. Dicentrine is absent from the latter and therefore appears to be of further diagnostic value to distinguish between the two species. The rich variety and yield of alkaloids in A. miersiana provide a rationale for its value as a medicinal plant.

The main alkaloids in leaves, stems and rhizomes of Antizoma angustifolia, a traditional medicinal plant of the family Menispermaceae, were isolated and identified. The main compound in leaves is almost invariably crotsparine, while stems and rhizomes have several other alkaloids (glaziovine, pronuciferine, bulbocapnine, salutaridine, cissacapine, insularine) in lower yields. These results do not agree with a previous study, where salutaridine was identified as the main alkaloid. Salutaridine was detected as a minor constituent of the rhizomes of only one of the samples. Alkaloids appear to be quite variable within different plant parts and different provenances of A. angustifolia, a fact that may explain the apparent absence of salutaridine in our samples.

Cassytha filiformis (Lauraceae), a widely distributed parasitic plant, contains several aporphine alkaloids and is often used in African folk medicine to treat cancer, African trypanosomiasis and other diseases. In a previous investigation, we showed that the alkaloid plant extract and the isolated aporphines possessed in vitro cytotoxic properties. In this paper, we evaluated the in vitro activity of the alkaloid extract (IC50 = 2.2 microg/mL) and its three major aporphine alkaloids (actinodaphnine, cassythine, and dicentrine) on Trypanosoma brucei brucei as well as four related commercially available aporphines (bulbocapnine, glaucine, isocorydine, boldine). Only the three alkaloids from Cassytha filiformis were active on the trypanosomes in vitro (IC50 = 3-15 microM). Additionally, we compared the cytotoxicity of these seven compounds on HeLa cells. Glaucine was the most cytotoxic compound on HeLa cells (IC50 = 8.2 microM) in the series. In order to elucidate their mechanism of action, the binding mode of these molecules to DNA was studied by UV absorption, circular and linear dichroism spectroscopy. The results of the optical measurements indicated that all seven aporphines effectively bind to DNA and behave as typical intercalating agents. Biochemical experiments showed that actinodaphnine, cassythine and dicentrine also interfere with the catalytic activity of topoisomerases in contrast to the four other aporphines. These interactions with DNA may explain, at least in part, the effects observed on cancer cells and on trypanosomes.

In this investigation the ability of free hydroxyl radicals generated via the reaction between an iron salt and H2O2 to degrade glyceryl trinitrate (GTN) was investigated. In a period of 27 h, GTN was completely degraded by free hydroxyl radicals when tested at 50 mg l−1 concentration. Degradation could not be accomplished by H2O2 or the iron salt alone. A free hydroxyl radical scavenger, bulbocapnine, completely inhibited the degradation of GTN supporting the conclusion that the hydroxyl free radicals may be responsible for the degradation of GTN. Our previous investigation revealed that a fungal culture, Penicillium corylophilum Dierckz, has the capability to completely degrade GTN within 308 h (Zhang, Y., Sundaram, S. T., Sharma, A. and Brodman, B. W. Applied and Environmental Microbiology 63(5): 1712–1714 (1997)1). In the present investigation, we studied the possibility of the involvement of free hydroxyl radicals in the biodegradation of GTN. This study was carried out with the inclusion of bulbocapnine in the fungal growth medium indicating that the free hydroxyl radicals were not involved in the degradation of GTN by P. corylophilum.

The aporphine isoquinoline alkaloid apomorphine is a potent inhibitor of the catalytic subunit (cAK) of rat liver cyclic AMP-dependent protein kinase (PKA), myosin light chain kinase (MLCK), and Ca(2+)- and phospholipid-dependent protein kinase C (PKC) (IC50 values 1, 11, and 8 microM, respectively). However, a number of O-methylated analogues of apomorphine are inactive or poor inhibitors of cAK. The benzophenanthridine isoquinoline alkaloid sanguinarine is a potent inhibitor of cAK but is a relatively poor inhibitor of PKC (IC50 values 6 and 217 microM respectively). However a number of methylated analogues of sanguinarine are inactive as cAK inhibitors. The aporphine isoquinoline alkaloids (+)-boldine and bulbocapnine are non-competitive inhibitors of MLCK with respect to both peptide substrate and ATP. The inhibition of cAK, MLCK, and PKC by apomorphine and sanguinarine is competitive with respect to ATP as substrate. The oxazine alkaloids darrow red, nile blue A, and oxazine 170 are variously effective as inhibitors of cAK, MLCK, PKC, and CDPK (IC50 values 4-65 microM). Ca2+ binds to apomorphine and (+)-boldine which, together with nile blue A and oxazine 170, are potent inhibitors of calmodulin (CaM)-dependent MLCK (IC50 values 11, 12, 4, and 7 microM, respectively), and interact with dansyl-CaM.

A simple RP-HPLC method was developed for the determination of jatrorrhizine, palmatine, corlumidine, bulbocapnine, bicuculline, protopine and tetrahydropalmatine in Corydalis decumbens and its preparations. Using chemically bonded ODS silical gel as the stationary phase, a mixture of acetonitrile and phosphate-triethylamine buffer (32:68) (pH 2.0), a mixture of acetonitrile, methanol and phosphate-triethylamine buffer (pH 3.0) (10:15:75) were suitable mobile phases for the separation of quaternary alkaloids and tertiary alkaloids, respectively.

Human dopamine D1a and D1b receptors were stably expressed in Baby Hamster Kidney (BHK) or Chinese Hamster Ovary (CHO) cells. [3H]SCH23390 saturation experiments indicated the presence of only a single binding site in the D1a expressing cell line with a Kd of 0.5 nM. In D1b expressing cell lines, two binding sites were observed with Kd values of 0.5 and 5 nM in CHO cells and 0.05 and 1.6 nM in BHK cells, respectively. Neither of the receptors affected Ca2+ metabolism whereas they both were coupled in a stimulatory fashion to adenylyl cyclase. The pharmacological profile of both the D1a and D1b receptors as assessed from inhibition of specific [3H]SCH 23390 binding was classical D1-like. Thus, benzazepine derivatives as well as the atypical neuroleptics, clozapine and fluperlapine, exhibited high affinity whereas D2 selective compounds like sulpiride and spiperone had low affinity for these receptors. Besides SCH 23390, only NNC 112, fluphenazine and bulbocapnine were able to discriminate between the two states of the D1b receptor. In case of the D1a receptor, the Ki values obtained in binding experiments were very similar to Ki values obtained from inhibition of dopamine stimulated adenylyl cyclase. In the D1b expressing cell line, the Ki values obtained from inhibition of the dopamine stimulated adenylyl cyclase indicated a significantly better correlation with the state of the D1b receptor showing high affinity for antagonists. In agreement with observations from binding experiments, dopamine was around 20 fold more potent in stimulating adenylyl cyclase via the D1b receptor as compared to the D1a receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Several in vitro criteria were used to assess whether three methylenedioxyphenyl (MDP) compounds, the isoquinoline alkaloids bulbocapnine, canadine, and protopine, are mechanism-based inactivators of CYP2C19. The recently reported fluorometric CYP2C19 progress curve analysis approach was applied first to determine whether these alkaloids demonstrate time-dependent inhibition. In this experiment, bulbocapnine, canadine, and protopine displayed time dependence and saturation in their inactivation kinetics with K(I) and k(inact) values of 72.4 ± 14.7 μM and 0.38 ± 0.036 min(-1), 2.1 ± 0.63 μM and 0.18 ± 0.015 min(-1), and 7.1 ± 2.3 μM and 0.24 ± 0.021 min(-1), respectively. Additional studies were performed to determine whether other specific criteria for mechanism-based inactivation were fulfilled: NADPH dependence, irreversibility, and involvement of a catalytic step in the enzyme inactivation. CYP2C19 activity was not significantly restored by dialysis when it had been inactivated by the alkaloids in the presence of a NADPH-regenerating system, and a metabolic-intermediate complex-associated increase in absorbance at approximately 455 nm was observed. In conclusion, the CYP2C19 progress curve analysis method revealed time-dependent inhibition by these alkaloids, and additional experiments confirmed its quasi-irreversible nature. This study revealed that the CYP2C19 progress curve analysis method is useful for identifying novel mechanism-based inactivators and yields a wealth of information in one run. The alkaloids bulbocapnine, canadine, and protopine, present in herbal medicines, are new mechanism-based inactivators and the first MDP compounds exhibiting quasi-irreversible inactivation of CYP2C19.

Alkaloid extracts from 12 plant species of the families Amaryllidaceae, Fumariacae and Papaveraceae were studied with respect to their acetylcholinesterase inhibitory activity and alkaloid patterns. Fifty-three alkaloids were identified by GC-MS, including known acetylcholinesterase (AChE) inhibitors such as galanthamine, epigalanthamine, sanguinine and epinorgalanthamine in extracts of Amaryllidaceae plants and protopine in extracts of Fumariaceae and Papaveraceae plants. The galanthamine-containing extracts of the amaryllidaceous plants were found to be the most active while the extract of Corydalis bulbosa was the most active among the extracts of the tested plants from the Fumariaceae and Papaveraceae plants. TLC bioautographic assay, preparative TLC and GC-MS analysis were combined to identify the active compounds in the studied extracts. Galanthamine was isolated from the known AChE inhibitors in the extracts of Amaryllidaceae plants. Corydaline, bulbocapnine and stylopine were found to be active in the extracts of plant species of the families Fumariaceae and Papaveraceae. Available standards of deshydrocorydaline--a precursor of corydaline, corydaline and stylopine--were tested for AChE inhibitory activity. Deshydrocorydaline and corydaline showed potent inhibitory activity comparable with that of the positive control galanthamine.

In the course of screening plants used in Danish folk medicine as memory enhancers, a crude methanolic extract of tubers from Corydalis cava showed significant acetylcholinesterase inhibitory activity in a dose-dependent manner. Activity guided fractionation of the methanolic extract resulted in the isolation of three alkaloids, bulbocapnine ( 1 ), corydaline ( 2 ) and corydine ( 3 ) as active constituents. Bulbocapnine inhibited acetylcholinesterase as well as butyrylcholinesterase in a dose-dependent manner with IC 50 values of 40 ± 2 μM and 83 ± 3 μM, respectively. Corydaline inhibited acetylcholinesterase in a dose-dependent manner with an IC 50 value of 15 ± 3 μM and corydine inhibited butyrylcholinesterase in a dose-dependent manner with an IC 50 value of 52 ± 4 μM. Corydaline was considered inactive against butyrylcholinesterase and corydine against acetylcholinesterase, due to IC 50 > 100 μM.

The aporphine alkaloids (+)-dicentrine and (+)-bulbocapnine are non-planar molecules lacking features normally associated with DNA binding by intercalation or minor groove binding. Surprisingly, dicentrine showed significant activity as a topoisomerase II (EC 5.99.1.3) inhibitor and also was active in a DNA unwinding assay. The DNA unwinding suggests DNA intercalation, which could explain the inhibition of topoisomerase II. Bulbocapnine, which differs from dicentrine only by the presence of a hydroxyl group at position 11 and the absence of a methoxyl group at position 9, was inactive in all assays. Molecular modeling showed that dicentrine can attain a relatively planar conformation, whereas bulbocapnine cannot, due to steric interaction between the 11-hydroxyl group and an oxygen of the methylenedioxy ring. These observations suggest that dicentrine is an “adaptive” DNA intercalator, which can bind DNA only by adopting a somewhat strained planar conformation. The requirement of a suboptimal conformation to achieve DNA binding appears to make dicentrine a weaker topoisomerase II inhibitor than the very planar oxoaporphine alkaloid liriodenine. These results suggest that it may be possible to modulate DNA binding and biologic activity of drugs by modifications affecting their ability to adopt planar conformations.

A new aporphine alkaloid, (+)-bulbocapnine-beta-N-oxide (1), was isolated from Glaucium fimbrilligerum. Its structure and the stereochemistry at the N-oxide center were determined by spectroscopic methods and confirmed by synthesis.

The effects of bulbocapnine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis in PC12 cells were investigated. Bulbocapnine showed 45.2% inhibition on dopamine content in PC12 cells at a concentration of 20 μ M for 12 h. The IC 50 value of bulbocapnine was 26.7 μ M. Bulbocapnine at concentrations up to 80 μ M was not cytotoxic towards PC12 cells. Tyrosine hydroxylase (TH) activity was inhibited by the treatment of bulbocapnine in PC12 cells (24.4% inhibition at 20 μ M). Bulbocapnine at 20 μ M also decreased the intracellular Ca 2+ concentration by 12.9% inhibition relative to control in PC12 cells. However, TH mRNA level was not altered by bulbocapnine treatment. These results suggest that the inhibition of TH activity by bulbocapnine might be involved in at least one component of the reduction of dopamine biosynthesis in PC12 cells.

Using antiplatelet aggregation as a guide to fractionation, seven aporphines, actinodaphnine (1), N-methylactinodaphnine (2), launobine (3), dicentrine (4), O-methylbulbocapnine (5), hernovine (7), and bulbocapnine (9), and two oxoaporphines, dicentrinone (6) and liriodenine (8), were isolated from the stems of Illigera luzonensis. Among them, compounds 2, 4, 5, 8, and 9 were isolated for the first time from this species. Moreover, compounds 1−5, 7, and 8 showed significant antiplatelet aggregation and compounds 1 and 6 exhibited significant vasorelaxant activities, respectively.

Although many studies have been carried out on the dopaminergic system, little is known about the dopaminergic system in the ovary. The present study was undertaken to investigate the role of the dopamine (DA) system in ovarian function especially in steroidogenesis using rat ovaries. Ovarian cells from PMS-treated rats were incubated for 1 hour with or without DA or other drugs. DA, norepinephrine (NE) and isoproterenol (Iso) increased the levels of progesterone (P4) and cAMP in the media. D1 agonists (SKF38393, SKF82526-J, CY208-243) increased P4 secretion, whereas bromocriptine (D2 agonists) did not show any effect on the P4 level in the media. The effect of NE and Iso on P4 and cAMP levels was inhibited by propranolol (Pro; beta-blocker), while the increase of P4 and cAMP levels caused by DA or D1 agonists was suppressed by bulbocapnine (Bul; D1 antagonists). Propranolol (beta-blocker) or domperidone (D2 antagonists) did not affect the levels of P4 and cAMP. The presence of dopamine D1 receptor in the PMS-treated rat ovary was revealed by a kinetic study. The maximal number of binding sites (Bmax) of ovarian D1 receptor was 1.33fmol/mg tissue and the Kd value was 0.357nM. These results suggest that the DA system may physiologically play a role in the steroidogenesis in the ovary through D1 receptor.

Little is known about the dopamine system in the ovary. The present study has been undertaken to investigate the effect of dopamine (DA) on the ovarian steroidogenic enzymes of pregnant mare serum gonadotropin (PMSG)-treated immature rats. Ovarian cells from PMSG-treated rats were cultured for 1-5 hours with or without DA, D1 agonists or bulbocapnine (Bul)(D1 antagonist). Progesterone (P) and estradiol (E2) in the media were assayed by specific RIAs. The enzyme activities were assayed by adding radioactive substrates in the media before incubation. DA and D1 agonists increased P in the media which was caused by the increment of 3 beta -hydroxysteroid dehydrogenase (3 beta -HSD) activity because cholesterol side chain cleavage enzyme (CSCC) activity showed no significant change. The stimulating effects of DA and DA agonists on P and 3 beta -HSD activity were inhibited by Bul. DA showed no effect on 17 alpha-hydroxylase activity. DA decreased 17.20 lyase activity, but this decrement was probably a non specific effect. DA alone did not affect the E2 level in the media and aromatase activity. The present results suggest that DA mainly stimulated 3 beta -HSD activity of the PMSG-treated rat ovary which regulated P synthesis.

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3(+)-ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.

The oxidation product obtained by treatment of bulbocapnine methyl ether (2a) with iodine in ethanol/water is not the tetradehydroaporphinium salt 4 as assigned by Gadamer & Kuntze, but a dimer of structure 3. Reduction of 3 with zinc in dilute sulfuric acid gives rac-bulbocapnine methyl ether, whereas reduction with complex hydrides affords the diastereomeric dimers 7a and 7b.

We examined the possibility that dopamine may play a role in nerve-mediated "off" responses of esophageal body (EB) and relaxations of lower esophageal spincter (LES) smooth muscle. The effects of dopamine, epinine, and dopamine antagonists on EB and LES smooth muscle were studied on these responses. Dopamine and epinine caused a dose-related fall in basal LES muscle tension and in amplitude of EB muscle "off" responses. Threshold dose for both was about 10(-7) M, and maximal dose was about 10(-4) M. At high concentrations, they also caused repetitive transient contractions of both LES and EB muscle after the period of inhibition. These effects were antagonized by haloperidol, 10(-5) M, and bulbocapnine, 10(-5) M, but were not influenced by propranolol, 10(-5) M, nor by phenoxybenzamine, 10(-5) M. Neither haloperidol nor bulbocapnine influenced responses to electrical field stimulation. Tetrodotoxin 10(-7) M abolished the responses to electrical field stimulation but did not antagonize the effects of dopamine and epinine. EB and LES smooth muscle contain a dopamine receptor. It is unlikely that dopamine is involved in responses to electrical field stimulation.

Opossum duodenum was cut into 2 mm X 1.5 cm strips. The strips cut along the oral-caudal axis were called longitudinal strips, while those cut 90 degrees to that axis were called circular strips. Dopamine produced contractions in both muscle layers. ED 50 for the longitudinal and circular muscle was 2.8 X 10(-6) M and 1.9 X 10(-5) M, respectively. The longitudinal muscle was 6.5 times more sensitive to dopamine than the circular muscle. The dopamine-produced contractions were completely blocked by phenoxybenzamine, 10(-4) M, and phentolamine, 10(-5) M. Haloperidol, 10(-5) M, or bulbocapnine, 10(-5), completely or partially blocked the contractions produced by dopamine in only one-third of the strips. Tetrodotoxin, propranolol, atropine, and curare did not affect the dopamine-produced contractions. These studies suggest that dopamine mainly stimulates alpha-excitatory adrenergic receptors in opossum duodenal muscle and that the longitudinal muscle is more sensitive to dopamine. However, we cannot exclude the existence of excitatory dopamine receptors in the opossum duodenal smooth muscle.

SK & F 38393 (2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine) is a new dopamine receptor agonist which selectively increased renal blood flow when administered i.v. to dogs at cumulative doses of 3.3-1333 microgram/kg. Consistent changes in arterial blood pressure heart rate and cardiac output were not observed. The renal response, which was mediated locally in the kidney, was not antagonized by adequate blocking doses of atropine, propranolol, metiamide and/or mepyramine nor by reserpinization or treatment with indomethacin. It was inhibited, however, by the selective peripheral dopamine receptor antagonist, bulbocapnine. Perhaps as a result of its action on renal blood flow, SK & F 38393 produced a diuresis in normally hydrated rats which was characterized by an increased excretion of sodium, potassium and chloride and a increased urinary pH. Compounds of this type may be useful in better defining dopaminergic receptors and in the treatment of disease states where renal ischemia is present.

Field stimulation of the parasympathetic nerves supplying the rabbit isolated rectococcygeus muscle produced individual twitch responses that were inhibited by dopamine (1 x 10(-8)-1 x 10(-5)M). The twitch-inhibitory effect of dopamine was reversed by haloperidol or sulpiride (1 x 10(-8)-1 x 10(-5)M for either) but not by phentolamine or yohimbine (up to 1 x 10(-4)M). Haloperidol and sulpiride were potent, specific, competitive antagonists of the twitch-inhibitory effect of dopamine; their pA2 values were 8.39 and 7.75, respectively. In contrast, cis alpha-flupenthixol, fluphenazine, bulbocapnine and thioridazine were weak or inactive against dopamine. Concentrations of dopamine that inhibited the twitch response to parasympathetic nerve stimulation had little or no effect on contractions elicited by carbachol or by direct muscle stimulation after abolition of neuronal conduction by tetrodotoxin. Thus, the effects of dopamine on responses elicited by parasympathetic nerve stimulation seem to be exerted at a prejunctional level rather than directly on the smooth muscle. The twitch-inhibitory effect of dopamine was mimicked by epinine, N,N-diethyldopamine, N,N-di-n-propyldopamine, 5,6-ADTN, N,N-di-n-propyl 5,6-ADTN, 6,7-ADTN, apomorphine and Sandoz 27-403. Sulpiride reversed the effects of all these agonists. N,N-di-n-propyl-6,7-ADTN and SK & F 82526 also inhibited the twitch response but their effects were not reversed by sulpiride. SK & F 38393 and DPI had little effect on the twitch response. The pharmacological characteristics of the presynaptic dopamine receptors in the rabbit rectococcygeus muscle show that they resemble those in the cat heart and rabbit ear artery in some respects but there are differences that suggest that the presynaptic dopamine receptors in the rabbit rectococcygeus muscle constitute a specific subgroup of receptors.

In rabbit pulmonary artery, dopamine (10(-11)-10(-5) M) produced a concentration-dependent relaxation of the arterial strips contracted with prostaglandin F2 alpha (PGF2 alpha) in the presence of prazosin (10(-6) M), yohimbine (10(-6) M), propranolol (10(-6) M), and methysergide (10(-6) M). SKF38393, an agonist for D1 or DA1 dopamine receptor, mimicked partially the concentration-response curve for dopamine, whereas LY171555 and apomorphine did not. The order of potency of dopamine antagonists on the inhibitory effect was: cis-flupenthixol greater than bulbo-capnine greater than metoclopramide greater than haloperidol. Sulpiride was inactive. Cis-flupenthixol did not block the relaxation induced by acetylcholine, adenosine, and papaverine. In the arterial strips of the rabbits pretreated with 6-hydroxydopamine, the concentration-response curve for dopamine was similar to that in non-treated rabbits. Thus it is concluded that a specific dopamine receptor is located on the postsynaptic muscle membrane of the rabbit pulmonary artery.

1. 1. The effects of the serotonin (5-HT) antagonists, cyproheptadine (CYP), methylsergide (UML), 5-methoxygramine (5-MOG), mianserine (MIA), l-(l-naphthyl)piperazine (NAP) and other receptor antagonists, chlorpromazine, bulbocapnine, imipramine, dibenamine and butaclamol (BUTA) on the relaxing response to 5-HT were investigated in the anterior byssus retractor muscle (ABRM) of Mytilus . 2. 2. CYP (p A 2 = 6.73 ± 0.02), UML (p A 2 = 6.43 ± 0.04) and 5-MOG (p A 2 = 5.65 ± 0.03) antagonized the relaxing response to 5-HT in a competitive manner, but the selective 5-HT 2 antagonists MIA and NAP did not. 3. 3. Of the other antagonists used, only BUTA (p A 2 = 5.65 ± 0.04) antagonized the relaxing response to 5-HT in a competitive manner. 4. 4. These findings suggest that the pharmacological properties of the 5-HT receptors of the ABRM subserving the relaxing response appear to be similar to those of the 5-HT 1 receptors of vertebrates, and dissimilar to those of 5-HT 2 receptors.

Psychotropic drugs such as methadone, morphine and bulbocapnine produce increments in dopamine metabolism as an unconditioned reflex. When a buzzer noise is used as a conditioned stimulus (CS) with these drugs as unconditioned stimuli, the buzzer CS acquires the properties of the drugs in increasing dopamine metabolism. These results suggest that the brain, like other visceral organs, can be conditioned in terms of neurotransmitter release or metabolism.

The synthesis of three new racemic aporphine alkaloids (1b, 1c and 2) is reported and these alkaloids are fully characterized. The method of synthesis involved either a Bischler-Napieralski-Psehorr sequence or a Reissert alkylation-Pschorr cyclization route. The Pschorr cyclization also gave the morphinandienones 7a and 7b, respectively.

(6aR)-1,2-(Methylenedioxy)aporphine-10, 11-diol (8) and (6aR)-aporphine-1, 1, 10, 11-tetrol (16) have been prepared from natural (S)-bulbocapnine (4). For both compounds, the partial synthesis included racemic intermediates which have been resolved into their enantiomers. Both compounds 8 and 16 showed dopaminergic activity in rats, although to a lower extent than (R)-apomorphine (1) itself.

The opening of a methylenedioxy group with simultaneous elimination of an oxygen atom during sodium in liquid ammonia reduction is a well established process in the aporphine alkaloid series1. It has furthermore been reported that phosphate esters of phenols are deoxygenated under similar reaction conditions2. The alkaloid bulbocapnine (1) contains an aromatic methylendioxy group and a phenolic hydroxy group; it thus seemed indicated to attempt the direct removal of two oxygen atoms by treating the phosphate ester 2 with an alkali metal in liquid ammonia. We now would like to give experimental details regarding this practical step which was summarized elsewhere3.

1 Noradrenaline and clonidine were applied by microiontophoresis to single neurones in the cerebral cortex and medullary reticular formation of anaesthetized rats.2 Of a total of 247 neurones studied, 79% of medullary units and 60% of cortical units responded in the same manner to both noradrenaline and clonidine. The usual response was a depression of neuronal firing rate.3 It proved possible to antagonize some responses to both substances by the microiontophoresis of bulbocapnine, whilst leaving unaffected similar responses to 5-hydroxytryptamine.4 On 13% of the cells, clonidine produced an increase of firing rate. This effect could not be attributed to a post-synaptic antagonism of tonically released endogenous noradrenaline, but may indicate a presynaptic action of clonidine, reducing noradrenaline release.5 These observations are thought to support the idea that clonidine may have an agonist action on noradrenaline receptors in the brain.

The author compared the functional properties of the striatal system in KM rats sensitive to the convulsive effects of sound with those in Wistar rats, which are insensitive to these effects. It was shown that bulbocapnine (an antagonist of dopamine) administered to the Wistar rats at a dose of 40 mg/kg body weight caused catalepsy, depressed the motor cortex excitability, and raised the threshold of the generalized Jacksonian-type convulsions. The KM rats showed neither catalepsy nor a rise in the generalized convulsion threshold, and the depression of the motor cortex excitability in them was only slight. Examinations of the apomorphine-induced stereotypy (dose 1.0-10 mg/kg) showed that in the KM rats the sensitivity of the receptors to dopamine was changed. The hyperproduction of catecholamines in the striatum, the hypothalamus, and adrenals in the KM rats suggests that the predisposition to epileptiform states correlates with the generalized defect in the metabolism of catecholamines. It is suggested that the hypersensitivity of KM rats to epileptogenic effects is due to a deficiency (caused by an excess of dopamine) in the depressing function of the striatum.

Bulbocapnine methyl ether (2), on treatment with boron halides, affords the aporphine-1,2-diol (3), the novel aporphines 5 and 6 or the phenanthrene derivative 11 depending on the reaction conditions. 3 can be further transformed into corydine methyl ether (4); 6 has been converted to corytuberine (8). Similarly, dehydrobulbocapnine methyl ether 9 was converted to 10.