Antiparkinsonian drug doses and neuroleptic receptors

Summary The clinical potency of 3 drugs, apomorphine, N-propylnorapomorphine, and bromocryptine, have been found to be closely correlated to their potencies in competing for³H-haloperidol and³H-spiroperidol both of which label the dopamine receptor. This correlation indicates that the direct binding assay may be used to predict clinical potencies of anti-parkinsonian drugs, and indicates that agonists as well as antagonists compete potently for³H-neuroleptic binding.This work was supported by the Ontario Mental Health Foundation, the W. Garfield Weston Foundation and the Medical Research Council of Canada.     

3H-Spiroperidol binding to striatal membranes of mutant Han-Wistar rats which exhibit spastic paresis

Summary The binding of³H-spiroperidol to striatal membranes from a strain of mutant Han-Wistar rats was compared with that in normal littermate animals. The specific binding was less in the mutants than the controls. Scatchard analysis revealed that the K_D- and B_max-values for the high affinity binding sites in the mutants are greater than for those in the controls. These findings indicate that the dopamine receptors of the mutants are affected and could explain some of the previous data; it has been suggested that some of the spasticity observed in the mutants may be due to an abnormal functioning of their dopaminergic neurones.     

Effect of isoprenaline on dopamine receptors in the rabbit isolated renal artery

Summary The relaxant effects of isoprenaline on rabbit isolated renal artery and aorta were compared. The results suggest that although isoprenaline acts on -adrenoceptors in the aorta it stimulates dopamine receptors in the renal artery.     

In vitro dopaminergic neuroprotective and in vivo antiparkinsonian-like effects of Δ3,2-hydroxybakuchiol isolated from Psoralea corylifolia (L.)

Cocktail recipes containing Psoralea corylifolia seeds (PCS) are used to empirically treat Parkinson disease. A PCS isolate Δ³,2-hydroxybakuchiol (BU) can inhibit dopamine uptake in dopamine transporter (DAT) transfected Chinese hamster ovary (CHO) cells, and dopamine reuptake blockade may provide an alternative approach for ameliorating parkinsonism. Here, we assessed the potential dopaminergic neuroprotective, and antiparkinsonian-like activity of BU. BU sample size was increased by using a scale-up extraction paradigm. Pharmacologically, BU significantly protected SK-N-SH cells from 1-methyl-4-phenylpyridinium (MPP⁺) insult, produced striking inhibitory actions on dopamine/norepinephrine uptake and WIN35,428 binding in synaptosomes on in vivo administration, and significantly preventing poor performance on rotarod and dopaminergic loss in substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mice. BU acts by protecting dopaminergic neurons from MPP⁺ injury and preventing against MPTP-induced behavioral and histological lesions in the Parkinson’s disease (PD) model, possibly by inhibiting monoamine transporters. These findings suggest that BU could be meaningful in PD treatment. Received 14 January 2009; received after revision 22 February 2009; accepted 10 March 2009     

Effects of dopamine antagonists on snail locomotion

Summary Dopamine antagonists which affect the ergometrine-sensitive type of dopamine receptors produce characteristic motor disorders in a land snail,Helix pomatia L.Acknowledgment. We are grateful to Dr L. Hiripi for valuable suggestions and Dr I. Varanka for help in photography.     

Juvenile hormone catabolism inManduca sexta: Homologue selectivity of catabolism and identification of a diol-phosphate conjugate as a major end product

We studied time-dependent metabolism of (10R)-[³H] juvenile hormone (JH) III and (10R, 11S)-[³H]JH I injected intoManduca sexta larvae; the hormones are metabolized to polar metabolites, expecially the JH acid-diol, and an unknown. Products were analyzed using a reversed-phase liquid chromatography assay. (10R)-JH III is metabolized much more rapidly than (10R, 11S)-[³H]JH I, whether injected seperately or as a mixture of hormones. The unknown metabolites of JH I and JH III were identified as phosphate conjugates of JH I and JH III diol by tandem mass spectral analysis of isolated samples. The phosphate conjugate of JH I diol is the principle end product of JH I metabolism.     

Enzymatische Unterschiede zwischen Myosin-ATPasen quergestreifter Kaninchenmuskeln

Summary The Ca²⁺ activated myosin-ATPase of white skeletal muscle of the rabbit has a much higher specific activity than the corresponding enzymes from red and cardiac muscle. The pH-dependence of the 3 myosin-ATPases is identical. However, they differ significantly in the extent of their inhibition by KCl. We conclude, therefore, that all 3 myosins are enzymatically dissimilar.     

Formation of 4,4′-methylene-bis(2-chloroaniline)-DNA adducts in yeast expressing recombinant cytochrome P450s

N-Oxidation of 4,4-methylene-bis(2-chloroaniline) (MBOCA) may lead to formation of DNA adducts. To determine if cytochrome P450s are involved in the formation of MBOCA derived-DNA adducts, yeast strains expressing rodent P450s were exposed to MBOCA, and³²P-postlabelling of nucleotides from yeast genomic DNA was done. Chromatographic analysis on PEI cellulose showed that, upon exposure to MBOCA for 1 h, nine DNA adducts were formed in yeast expressing phenobarbital-inducible rabbit P450 2B5. With a 4-h-exposure, all adducts increased in parallel. In cell-free experiments, the incubation of MBOCA with phenobarbital-induced rat microsomal fraction followed by incubation with thymus DNA, led to the formation of more than ten DNA adducts. When yeast expressing 3-methylcholanthrene-inducible rat P450 1A1 was exposed to MBOCA, one major and two minor adducts were formed. No adducts were detected in control yeast. These results show that recombinant rabbit P450 2B5 exhibits a potential activation of MBOCA and that rat P450 1A1 has some effect. The use of yeast expressing recombinant P450s and the technique of³²P-postlabelling facilitates a simple search for chemicals with carcinogenic potential.     

High sensitivity of porcine cerebral arteries to endothelin

Summary The threshold concentration of endothelin to induce contractions in porcine cerebral arteries (anterior cerebral, Willis ring and basilar artery) was lower than those for coronary and renal arteries. The median effective concentrations (ED₅₀) of endothelin in cerebral arteries were also significantly lower than those for coronary and renal arteries. There was no significant difference in the sensitivity to endothelin among cerebral arteries, or between coronary and renal arteries. The maximal percentage of contractions induced by endothelin, as compared to that induced by 10^–1 M potassium chloride, was not significantly different between the arteries.     

Influence of dopamine infusion on plasma prolactin released by kidney capsule transplanted anterior pituitaries

Summary The infusion of dopamine into the renal artery resulted in decreased prolactin release from 3 anterior pituitary glands transplanted under the kidney capsule. Prolactin levels continually decreased over a 5 min period after DA infusion was terminated and thereafter approached preinfusion levels by the end of 10 min.Supported by NSF Research, grant No. 74-17332.The authors wish to express their appreciation to Mrs Cynthia Van De Walle for her outstanding technical assistance in the performance of the prolactin RIA and the statistical analyses. We also appreciate receiving as a gift from the National Institute for Arthritis, Metabolism and Digestive Diseases the rat prolactin used for iodination (RP-I₂) and standards (RP-1).     

Multiple daily amphetamine administration decreases both [3H]agoinst and [3]antagonist dopamine receptor binding

Summary Multiple daily amphetamine injections in rats decreased both [³H]agonist as well as [³H]antagonist striatal dopamine receptor binding. Concurrently, these animals exhibited a decrease in striatal dopamine concentration and, paradoxically, an enhancement of behavioral responsivity.This study was supported by PHS grant MH32990 to I.C. and DA0156805 to D.S.I. Creese and D. Segal are the recipients of the RSDA grants MH00316-01 and RSDA MH70183-08, respectively.     

Differential sensitivity of the two phases of ear artery contraction to intimal and adventitial norepinephrine

Summary The biphasic contraction of the rabbit ear artery to norepinephrine (NE) was investigated in the normal (adventitial stimulation) and the everted (intimal stimulation) segment of ear artery. The 2nd phase response showed an intimal ED₅₀ of 8.2×10^–8 M which was significantly (p<0.05) lower than the adventitial ED₅₀ of 42.6×10^–8 M. This difference was abolished by inhibition of neuronal and extraneuronal uptake for NE. The 1st phase response also showed an ED₅₀ for the intimal stimulation (6.9×10^–8 M) which was significantly (p<0.05) lower than adventitial (65.5×10^–8 M). This difference was reduced but not abolished by NE uptake inhibition. This suggsets that some feature of the adrenergic neuroeffector apparatus is asymmetrically arranged to favor fast responses to blood borne NE.Supported by American Heart Association-Greater Los Angeles Affiliate Grant No. 602. We wish to thank Dr John Bevan and Dr Alasdair MacLean for helpful advice.     

Endothelium-dependent relaxation induced by sodium fluoride in the rabbit ear artery

Summary Sodium fluoride (NaF) produced concentration-dependent relaxation of isolated rabbit ear artery precontracted with norepinephrine. In contrast, an arterial preparation with the endothelium rubbed off did not relax, but contracted in response to NaF. NaF-induced relaxation was not influenced by indomethacin but was inhibited by methylene blue or N^G-monomethyl-L-arginine. The results indicate that NaF relaxes the artery by releasing a so-called EDRF.     

The endocannabinoid system in rat gliosomes and its role in the modulation of glutamate release

The endocannabinoid system and endocannabinoid receptor-driven modulation of glutamate release were studied in rat brain cortex astroglial gliosomes. These preparations contained the endocannabinoids N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol, as well their major biosynthetic (N-acyl-phosphatidylethanolamines-hydrolyzing-phospholipase D and diacylglycerol-lipase) and catabolic (fatty acid amide-hydrolase and monoacylglycerol-lipase) enzymes. Gliosomes expressed type-1 (CB1R), type-2 (CB2R) cannabinoid, and type-1 vanilloid (TRPV1) receptors, as ascertained by Western blotting and confocal microscopy. Methanandamide, a stable analogue of anandamide acting as CB1R, CB2R, and TRPV1 agonist, stimulated or inhibited the depolarization-evoked gliosomal [³H]d-aspartate release, at lower and higher concentrations, respectively. Experiments with ACEA (arachidonyl-2′-chloroethylamide), JWH133 ((6aR,10aR)-3-(1,1-dimethylbutyl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]-pyran) and capsaicin, selective agonists at CB1R, CB2R and TRPV1, respectively, demonstrated that potentiation of [³H]d-aspartate release was due to CB1R while inhibition to CB2R and TRPV1 engagement. These findings were confirmed by using selective receptor antagonists. Furthermore, CB1R activation caused increase of intracellular IP3 and Ca²⁺ concentration, suggesting an involvement of phospholipase C.     

L'action du dithizone sur la rétine du lapin Etude électrophysiologique

Summary Dithizone provokes chorio-retinal lesions in the rabbit, visible ophthalmoscopally after 12 h and microscopally after 8 h. The ERG reveals much earlier alterations, theb wave diminishes rapidly and the ERG is abolished in 3 to 4 h. In the cases where no durable lesions are noted, the ERG is nevertheless pathological, theb wave being diminished 40 to 70% of its initial value during the first day, but becoming normal once again even if a permanent diabetes results. These anomalies of the ERG are related to acute hypoglycaemia and enzymatic blockage.

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Travail subventionné par la FondationEmil Barell (Bâle).     

Dopamine and octopamine in whole body extracts of the bulb mite

Summary Using high performance liquid chromatography with electrochemical detection, whole body extracts of the bulb mite,Rhizoglyphus echinopus (Fumouze and Robin), were found to contain the biogenic amines dopamine and octopamine at concentrations of 4.3±0.6 and 2.3±1.4 ng g^–1 wet weight, respectively. Adrenaline, noradrenaline, tyramine,N-methyldopamine,N-acetyldopamine, and 5-hydroxytryptamine, if present, were below the limits of detectability. This is the initial demonstration of the presence of octopamine in a mite species.     

Aging and endothelin-1 induced vascular contractions

Summary Contractions produced by endothelin-1 (0.3–30 nM) have been investigated in aorta, renal arteries and mesenteric arteries from 2- and 24-month-old Sprague-Dawley rats. In senescent rats the EC₅₀ values of endothelin-1 for aorta and renal artery were significantly increased (aorta: from 6.2 to 12 nM; renal artery: from 5.2 to 7.8 nM). For mesenteric artery the EC₅₀ value (4.3 nM) was unchanged by aging, whereas the maximal contractile response to endothelin-1 was enhanced (from 8.3 to 11.7 mN). In contrast, there was no significant age-related difference in the maximal endothelin-1 response of aorta and renal artery. The present data demonstrate a reduced sensitivity for aorta and renal artery and an enhanced maximal response to endothelin-1 in the mesenteric artery in senescent rats.     

Similarities between metallothionein and low molecular weight testicular cadmium-binding protein

Summary The incorporation of³⁵S-cysteine and³H-glutamic acid was studied in mouse hepatic and renal metallothionein and in testicular cadmium-binding protein of similar molecular weight. Preferential incorporation of³⁵S-cysteine over³H-glutamic acid was observed not only in hepatic and renal metallothionein, but also in testicular cadmium-binding protein. When the antigenic reactivity of these proteins was compared, all three proteins reacted with the metallothionein antibody. These similarities suggest that the low molecular weight testicular cadmium-binding protein is apparently metallothionein.     

In pre-sterol carrier protein 2 (SCP2) in solution the leader peptide 1 – 20 is flexibly disordered, and residues 21 – 143 adopt the same globular fold as in mature SCP2

The preform of the rabbit sterol carrier protein 2 (pre-rSCP2) was cloned, the uniformly ¹⁵N-labelled protein expressed in Escherichia coli and studied by three-dimensional ¹⁵N-resolved nuclear magnetic resonance spectroscopy. In spite of its low solubility in aqueous solution of only ∼0.3 mM, sequential ¹⁵N and ¹H backbone resonance assignments were obtained for 105 out of the 143 residues. From comparison of the sequential and medium-range nuclear Overhauser effects (NOEs) in the two proteins, all regular secondary structures previously determined in mature human SCP2 (hSCP2) [Szyperski et al. (1993) FEBS Lett. 335: 18–26] were also identified in pre-rSCP2. Near-identity of the backbone ¹⁵N and ¹H chemical shifts and 1 : 1 correspondence of 24 long-range NOEs to backbone amide groups in the two proteins show that the residues 21 – 143 adopt the same globular fold in pre-rSCP2 and mature hSCP2. The N-terminal 20-residue leader peptide of pre-rSCP2 is flexibly disordered in solution and does not observably affect the conformation of the polypeptide segment 21 – 143. Received 11 May 1998; accepted 15 May 1998     

Inhibition by tetanus and botulinum A toxin of the release of [3H]noradrenaline and [3H]GABA from rat brain homogenate

Summary Rat brain homogenate was preloaded with [³H]noradrenaline or [³H]GABA and stimulated with high K⁺. Tetanus toxin and botulinum A neurotoxin partially prevent the evoked [³H]noradrenaline release in the same range of toxin concentrations starting below 10^–10M. In contrast, release of -amino butyric acid (GABA) is much more sensitive to tetanus than to botulinum A toxin.