摘要:

Abstract:The association of neurotensin to its receptor in differentiated neuroblastoma N1E115 cells led to a fast and transitory increase of the intracellular concentration in inositol trisphosphate and inositol bisphosphate, followed by a slower and more stable increase in inositol monophosphate. The action of inositol 1,4,5‐trisphosphate on digitonin‐permeabilized N1E115 cells resulted in a stimulation of cyclic GMP levels that mimicked that induced by neurotensin. Therefore, the cyclic GMP stimulation is probably a consequence of the initial inositol trisphosphate formation triggered by neurotensin. Fluoroaluminate ions and pertussis toxin had the capacity to modulate positively and negatively, respectively, the formation of inositol trisphosphate induced by neurotensin, indicating that GTP‐binding proteins are involved in the regulation of inositol phosphate levels by neurotensin rece

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09986.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:We have previously shown that a partially purified μ opioid receptor from bovine brain requires lipids to exhibit full binding activity. In the present report, we have determined the specificity of this lipid requirement. Lipids active in this regard were found always to contain an acidic head group and a fatty acid with two or more double bonds. Free, polyunsaturated fatty acids were also able to confer high binding activity on the partially purified opioid receptor. The possible roles lipids play in opioid binding are discussed in light of these data

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09987.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:[14C]Acetylcholine (ACh) release and parallel alterations in45Ca2+uptake and intrasynaptosomal free Ca2+concentration ([Ca2+]i) were measured in guinea‐pig brain cortex synaptosomes. Depolarization by high K+concentrations caused a rapid transient increase in Ca2+uptake, terminating within 60 s (rate constant = 0.060s‐1; t1/2= 11.6 s). This resulted in a rapid increase (within 1 s) in [Ca2+]i, which then fell to a maintained but still‐elevated plateau level (t1/2for the decline was 15 s). Peaks of [Ca2+]ishowed a sigmoidal dependence on depolarization, contrasting with the simple linear dependence of plateau levels of [Ca2+]i. The K+‐evoked ACh release also had two phases: a fast initial increase (t1/2= 11.3 s), which terminated within 60 s, was followed by a slow additional increase during sustained depolarizations of up to 10 min. Depolarization by veratridine led to a slow gradual increase in Ca2+uptake (t1/2= 130 s) over a 10‐min incubation period, whereas an elevated plateau level of [Ca2+]iwas achieved within 2 min (without a rapid peak elevation). The Ca2+‐dependent fraction of the veratridine‐evoked ACh release correlated with the increase in [Ca2+]irather than with Ca2+uptake. Using two different methods of depolarization partially circumvented the time limitations imposed by a buffering Ca2+indicator and we suggest that, in the main, ACh is released in bursts associated with [Ca2

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09988.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The effects of some anticonvulsant drugs have been investigated on γ‐hydroxybutyrate release from rat hippocampal and striatal slices. Sodium valproate and ethosuximide inhibited the depolarization‐evoked release of γ‐hydroxybutyrate induced by 40mMK+. The IC50values for these two drugs are in the concentration range of valproate and ethosuximide that exists in rat brain after administration of anticonvulsant doses to the animals. Trimethadione and pentobarbital are without significant effects. It can be concluded that the inhibition of γ‐hydroxybutyrate release, particularly that observed for hippocampus, might explain the protective effect of valproate and ethosuximide on γ‐hydroxybutyrate‐induced seizures and perhaps on other kinds of epilep

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09989.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The distribution of high‐affinity binding sites for γ‐[3H]hydroxybutyrate in coronal sections of rat brain was studied by quantitative autoradiographic techniques. Binding sites for this naturally occumng substance, which may possibly have a neurotransmitter role, are concentrated in some restricted areas of the brain, particularly in the limbic system. The hippocampus (especially field CAI of Ammon's horn, at 292 fmol/mg of tissue), septum (72 fmol/mg of tissue), and cortex (frontal, 113 fmol/mg of tissue; parietal, 103 fmol/mg of tissue; cingulate, 114 fmol/mg of tissue; and entorhinal, 134 fmol/mg of tissue) show pronounced labeling with γ‐[3H]hydroxybutyrate. Binding is much lower in caudatus‐putamen (50 fmol/mg of tissue), thalamus, and hypothalamus. Caudal parts of the brain (cerebellum, pons, and medulla) are practically devoid of binding sites. These results strongly support a functional role of endogenous y‐hydroxybutyrate in particularly restricted areas of th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09990.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A novel type of rotating disc electrode and a flow cell with laminar flow pattern were developed and applied to the electrochemical detection of dopamine, 3,4‐dihy‐droxyphenylacetic acid, homovanillic acid, 3‐methoxytyra‐mine (3‐MT), noradrenaline, 3‐methoxy‐4‐hydroxyphenyl‐ethyleneglycol (MOPEG), 5‐hydroxytryptamine (5‐HT), and 5‐hydroxyindoleacetic acid after HPLC of these compounds. The active surface of the rotating disc working electrode was made from solid paraffin (40%; wt/wt) and graphite powder (60%; wt/wt). The sensitivity of the detector was proportional to the square root of the angular velocity and was practically independent of the flow rate of the mobile phase. The surface of the working electrode was very large (radius = 12 mm), and so the percentage of oxidation was 24–67%; (flow rate = 1.0 ml/min), depending on the compound. Electrical noise between 20 and 40 pA and background current of 20–60 nA were observed. In practice, the sensitivity for the detection of the compounds examined here was 8–16 nA/ng, and so a detection limit of 5 pg/injection could be achieved, when the detector was combined with reversed‐phase HPLC. Supernatants obtained from the extracts of the tissue samples (nine brain parts of rat brain were studied) were purified by using Sephadex G‐10 gel chromatography. Before this procedure, the proteins of the tissue extracts were precipitated by 0.2MHC1O4, and the excess of HC1O4was precipitated by KOH/HCOOH buffer. Simultaneously, the pH of the extracts was set to 2.4 by the above buffer. Adjustment of the pH was necessary so that elution of 5‐HT from the Sephadex G‐10 columns in the same fraction with 3‐MT was avoided. If these compounds were in the same solution, their peaks would overlap on HPLC. MOPEG sulfate was purified by diethylaminoethyl‐Sephadex A‐25 (anion exchange resin) from the first fraction collected from the Sephadex G‐10 columns. The contents of the compounds under investigation in nine brain parts a

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09991.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:This study examined the effects of dopamine D1and D2receptor agonists and antagonists on the spontaneous and calcium‐dependent, K+‐induced release of γ‐[3H]‐aminobutyric acid ([3H]GABA) accumulated by slices of rat substantia nigra. SKF 38393 (D1agonist) and dopamine (dual D1/D2agonist) were without effect on [3H]GABA efflux by themselves (1–40 μM), or in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX) (0.5 μM), but potentiated evoked release in the presence of forskolin (0.5 μM), an adenylate cyclase activator. These increases in release were prevented by the D1antagonist SCH 23390 (0.5 μM), but not by the D2antagonist metoclopramide (0.5 μM), Higher concentrations of forskolin (10–40 μM) augmented stimulus‐evoked [3H]GABA release directly, whereas dibutyryl cyclic AMP (100–200 μM) depressed it. Apomorphine, noradrenaline, and 5‐hy‐droxytryptamine (1–40 μM) had no effect. The D2stimulants lisuride, RU 24213, LY 171555, and bromocriptine dose‐dependently inhibited depolarisation‐induced but not basal [3H]GABA outflow. These inhibitory responses were not modified by the additional presence of SKF 38393 (10 μM) or SCH 23390 (1 μM), or by injection of 6‐hydroxydopamine into the medial forebrain bundle 42 days earlier, but were attenuated by metoclopramide (0.5 μM). Higher amounts (10 μM) of SCH 23390, metoclopramide, or other D2antagonists (loxapine, haloperidol) reduced evoked GABA release by themselves, probably by nonspecific mechanisms. These results suggest D1and D2receptors may have opposing effects on nigral GABA output and could explain the variable effects of mixed D1/D2dopaminomimetics in earlier rele

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09992.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:A 56,000‐dalton protein with inherent phospho‐protein phosphatase activity was isolated from porcine brain capillaries. The enzyme is not activated by divalent metal ions but strongly inhibited by zinc ions. As phosphatase inhibitor 2 readily inhibits the enzymatic activity, the protein can be classified as a type I phosphatase. The protein is stable toward protease treatment. Limited digestion with trypsin does not convert the enzyme into an active form of lower molecular weight. The physical and enzymatical properties of the phosphatase exhibit considerable similarities to those of another 56,000‐dalton phosphatase derived from rabbit reticulo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09993.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:The fate of tetanus toxin bound to neuronal cells at 0°C was followed using an anti‐toxin125I‐protein A assay. About 50%; of surface‐bound toxin disappeared within 5 min of warming cells to 37°C. Experiments with125I‐toxin showed that much of this loss was due to dissociation of bound toxin into the medium. Some toxin was however rapidly internalised, and could be detected only by permeabilising cells with Triton X‐100 prior to assay. To investigate the mechanism of internalisation, tetanus toxin was adsorbed to colloidal gold. Toxin‐gold was shown to be stable, and to recognise the same receptor(s) as free toxin. Quantitation of the distribution of toxin‐gold particles bound to the cell body at 4°C showed that it was concentrated in coated pits. After 5 min at 37°C, toxin‐gold appeared in coated vesicles, endosomes, and tubules. After 15 min, it was found largely in endosomes, and at 30 min in multivesicular bodies. The involvement of coated pits in internalisation of tetanus toxin, but not cholera toxin, was confirmed using the free toxins, anti‐toxins, and protein A‐gold. Toxin‐gold also entered nerve terminals and axons via coated pits, accumulating in synaptic vesicles and in‐traaxonal unco

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09994.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Abstract:Previous studies have indicated that the brains of DBA/2J (D2) mice have a more heavily myelinated CNS than those of C57BL/6J (B6) at postnatal days 17–21. However, the amount of myelin in the brains of F1 (B6 × D2) hybrids is even higher than in their parental strains. To investigate further factors involved in regulating myelino‐genesis in these mice, we have focused on the synthesis of cerebrosides and sulfatides, galactolipids enriched in myelin. Brain slices from 14‐, 17‐, and 21‐day‐old D2, B6, and F., mice were incubated with [3H]galactose and [35S]sulfate. After incubation, microsomes, myelin, and oligodendroglial cells were isolated, and the galactolipids were analyzed. At 21 days of age, the labeling of cerebrosides in F1mice was higher than in D2 and B6 mice when the results were expressed as microsomal or myelin radioactivity per gram wet weight. At 14 and 17 days of age, the labeling of cerebrosides in F1animals was similar to that in D2 mice and was considerably higher than that in B6 mice. The labeling of sulfatides in F1animals was significantly higher than in the B6 parent at all ages studied, whereas it remained higher than that in the D2 parent only at 17 days of age. A similar relationship among the strains was observed when the synthesis of myelin galactolipids was estimated by measuring the in vitro activity of UDP‐galactose:ceramide galactosyltransferase and 3′‐phosphoadenylyl sulfate:galactosylceramide 3′‐sulfotransferase. The results indicate that the increased accumulation of myelin galactolipids previously reported in the F1mice is partially due to enhan

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1987.tb09995.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY