摘要:

Abstract:The dipeptide carnosine (β‐alanyl‐L‐histidine) has been proposed as a neurotransmitter in the mammalian olfactory pathway. Therefore, the efflux ofin vivo‐synthesized [14C]carnosine from mouse olfactory bulb synaptosomes was investigated. Carnosine was found to be released from the olfactory bulb synaptosomes by two mechanisms. The first is a slow spontaneous process that is independent of depolarization. The rate of this release was doubled in the presence of 1 mMexternal carnosine. Release by the second mechanism was markedly stimulated in the presence of calcium by depolarization with either 60 mMK+or 300 μMveratridine. Omission of calcium abolished the stimulatory effect of both of these agents. Further, blockage of the veratridine‐induced depolarization by tetrodotoxin also inhibited carnosine release. These results are consistent with the hypothesis that carnosine acts as a neurotransmitter in the mouse olfact

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06626.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:125I‐Tyr1‐somatostatin binds reversibly, in a saturable manner, and with high affinity to membranes from rat brain. Kinetic and saturation data measured at equilibrium lead toKDvalues of 0.4 nM for cortical membranes. The binding is not affected significantly by seven neuropeptides and drugs unrelated structurally to somatostatin (SRIF) while native SRIF, Tyr1‐SRIF, and D‐Trp8‐D‐Cys14‐SRIF displace125I‐Tyr1‐SRIF in a dose‐dependent manner, withKiof 0.23 nM, 0.90 nM, and 0.11 nM, respectively. Binding sites for125I‐Tyr1‐SRIF were found in 9 out of 11 central structures; there was a significant correlation between binding capacity and endogenous SRIF levels measured by radioimmunoassay. In each of the two structures containing the most binding sites, the cortex and the preoptic area, Scatchard analysis suggests a single population of sites with apparent affinities of 0.8 nMand 1.4 nM, respectively. Subcellular fractionation of these two regions reveals that more than 60% of125I‐Tyr1‐SRIF specific binding of the homogenate is found in the crude mitochondrial pellet (P2), which contains synaptosomes. When P2is further fractionated on a discontinuous sucrose gradient, most of the initial P2binding is recovered from membrane fractions. Each of nine SRIF analogs, with a single alanine substitution, displaces125I‐Tyr1‐SRIF binding on cortical membranes in the same order of potency as on adenohypophyseal membranes (r= 0.84). The data demonstrate the presence of SRIF binding sites in the rat brain, with kinetic characteristics comparable to those found in the adenohypophysis, and they provide a biochemical basis for the mult

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06627.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Membrane‐bound opiate receptors from neuroblastoma‐glioma hybrid cells and from different parts of the rat brain (whole brain minus cerebellum, cortex, thalamus‐hypothalamus and cerebellum) were labeled with the methionine‐enkephalin analogue, D‐[3H]Ala2‐Met‐enkephalinamide, and solubilized with the nonionic detergent Brij 36T. The protease inhibitors bacitracin, phenylmethylsulfonyl fluoride, Trasylol, and leupeptin were included in the solubilization buffer to minimize proteolysis. Two simple techniques, ammonium sulfate precipitation and activated charcoal absorbence, were adapted to separate the free and the macromolecule‐bound ligands. The solubilized receptor‐[3H]enkephalin complexes were partially purified by consecutive passages through Sephadex G‐75 and Sepharose 6B columns. Of the three peaks of radioactivity that were observed in the effluent of the Sepharose column, two contained proteins, and one of them, with a Stokes radius of 59 Å, seemed to contain the specific opiate receptor, as evidenced by additional experiments. This peak was further purified on thiol‐Sepharose or diethylaminoethanol‐Sephadex columns that were eluted with a gradient of 0–50 mMdithiothreitol or with 1.0MKCI, respectively. The receptor‐[3H]enkephalin complex from neuroblastoma‐glioma cells (apparent δ‐type receptors) binds less to the thiol‐Sepharose beads than receptor‐(3H]enkephalin prepared from the hypothalamus‐thalamus, which is rich in μ receptors. The [3H]enkephalin receptor complexes of the various sources also differed in their stability. The dissociation of the ligand from the neuroblastoma‐glioma receptor was monophasic, with a half‐ life of 250 min, whereas that of two brain regions was biphasic, with half‐lives of 195–330 min and 10,000 min. The methods described may be of use for further purification of soluble opiate recept

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06628.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Phenylacetic acid, the major metabolite of phenylethylamine, has been identified and quantitated in rat brain regions by capillary column high‐resolution gas chromatography mass spectrometry. Its distribution is heterogeneous and correlates with that of phenylethylamine. The values obtained were (ng/g ± SEM): whole brain, 31.2 ± 2.7; caudate nucleus, 64.6 ± 6.5; hypothalamus, 60.1 ± 7.4; cerebellum, 31.3 ± 2.9; brainstem, 33.1 ± 3.3, and the “rest,”

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06629.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Polypeptides derived from human white matter membranes reacted with the radioiodinated lectins concanavalin A,Lens culinarisphytohemagglutinin,Ricinus communisagglutinin and wheat germ agglutinin after electrophoresis in polyacrylamide pore gradient gels. The molecular weights of these lectin‐reactive bands were estimated by comparison with radioiodinated protein standards by using the linear relationship between log of the molecular weight and log of the gel concentration reached by the protein after electrophoresis in a polyacrylamide gradient gel. The molecular weight estimates for components reactive with concanavalin A were 176,800, 141,200, 72,800, 52,800, 44,700, 40,000, 24,800 and 23,900. The molecular weights of the bands reactive with both wheat germ agglutinin andLens culinarisphytohemagglutinin were 138,000, 113,500, 92,100, 52,800, 44,700, 24,800 and 23,900. Wheat germ agglutinin was bound also to a band with a molecular weight of 72,800.Ricinus communisagglutinin bound to bands with estimated molecular weights of 138,000, 72,800, 52,800, 44,700, 24,800 and 23,900. The electrophoretic pattern of lectin‐reactive polypeptides derived from normal‐appearing white matter of multiple sclerosis brains was not qualitatively different from the lectin‐binding pattern of control brain membrane polyp

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06630.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Adenylate cyclase inDrosophila melanogasterheads is stimulated 5–6‐fold by low concentrations of octopamine. The octopamine stimulation is inhibited by low concentrations of the α‐adrenergic ligands phentolamine and dihydroergotamine and of chlorpromazine, but not by low concentrations of the β‐antagonist propranolol and by the α‐antagonist yohirnbine.d‐Tubocurarine enhances the octopamine effect. Tyramine, norepinephrine, and epinephrine also stimulate the cyclase, probably via the octopamine receptor. Serotonin and dopamine stimulateDrosophilaadenylate cyclase 1.3‐1.4‐fold; at least the latter putative neurotransmitter seems to interact with a receptor distinct from the octopamine receptor. Prolonged incubation with dopaminein vitroabolishes adenylate cyclase basal activity as well as responsiveness to guanyl nucleotides, NaF, and putative

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06631.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:[3H]Dihydroergocryptine ([3H]DHE) binds to a particulate preparation fromDrosophila melanogasterheads at a level of 2.4 ± 0.4 pmol/mg protein, with an apparent dissociation constant of 2.0 ± 0.5 nM. The binding sites are inactivated by heat, pronase treatment, detergents, and sulfhydryl and disulfide reagents. [3H]DHE binding is inhibited by low concentrations of serotonergic and α‐adrenergic ligands. The specificity of the binding sites, as revealed by displacement studies, differs from that of [3H]DHE binding sites in various vertebrate tissues. The [3H]DHE binding sites may correspond to serotonergic receptors, and possibly, to additional classes of receptors for putative neurotransmitters inDrosop

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06632.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:α‐Latrotoxin (α‐LT), the major component of black widow spider venom, is a high‐molecular‐weight protein that acts presynaptically by stimulating the release of stored neurotransmitters. The purified toxin was iodinated to high specific radioactivity by the Bolton‐Hunter procedure, without appreciable loss of biological activity. By the use of the125I‐toxin, specific receptors were revealed in synaptosome fractions isolated from various regions of the rat brain, but not in nonneural tissues. The density of α‐LT receptors [which are probably composed of, or include, membrane protein(s)] varies between 0.6 and 0.88 pmol/mg of synaptosome protein, their affinity is very high (KAof the order of 1010M−1), their association rate is fast, and their dissociation rate slow. They might belong to a single, homogeneous class. This last conclusion, however, is still uncertain, because results suggesting a possible heterogeneity were obtained by studying the dissociation of the toxin from synaptosomes incubated in high‐salt buffer. Experiments in which the binding of α‐LT and its dopamine release activity in striatal synaptosomes were investigated in parallel in a variety of experimental conditions support the hypothesis that occupation of the high‐affinity receptors is the initial step in the α‐LT activation

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06633.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:γ‐Hydroxybutyrate (GHB) is a compound with numerous neuropharmacological properties. The discovery of its biosynthetic system, together with its endogenous repartition, have prompted its possible implication in neurotransmission. This role is also supported by the existence, reported here, of a high‐affinity uptake system for GHB (Km= 46.4 μM)in both purified brain plasma membrane vesicles and in the crude mitochondrial fraction. GHB uptake is dependent on a Na+gradient but is independent of the membrane electrical potential. Cl−and K+can also modulate the uptake. As an approach to determine the conformation required for GHB uptake, a series of related compounds, including aryl‐or alkyl‐derivatives, has been examined for ability to inhibit GHB uptake. The regional distribution of uptake is also indicative of its possible physiological role, since in striatum, an area where GHB has a known pharmacological effect on dopaminergic neurons, this uptake activity is

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06634.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The effects of moderate and severe degrees of iron deficiency on brain and liver nonhaem iron levels and 5‐hydroxytryptamine (serotonin; 5‐HT) uptake by synaptic vesiclesin vitrowere investigated in experimental rats. Data obtained suggested that in both moderate and severe forms of iron deficiency, 5‐HT uptake by brain synaptic vesicles is decreased and is accompanied by a reduction in brain and liver nonhaem iron levels. On repletion with iron for 4 weeks, the deficient group of rats showed a normalisation of 5‐HT uptake by synaptic vesicles and liver nonhaem iron content, whereas the brain nonhaem iron concentration still showed a significant deficit. The data thus suggest that changes in the uptake of 5‐HT by brain synaptic vesicles that accompany iron depletion and repletion are more rapid than changes in the total nonhaem iron concentration in the brain. The observation that 5‐HT uptake by brain synaptic vesicles is decreased in iron deficiency suggests a probable role for iron in 5‐HT storage

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb06635.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY