SEARCH · PubMed Health

Results for “synaptosomes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 361 records · Page 20Linked to original sources

PubMed1978

Topography of glycoproteins in the chick synaptosomal plasma membrane.

Chick brain synaptosomes or synaptic subfractions were treated with neuraminidase (EC 3.2.1.18) and/or galactose oxidase (EC 1.1.3.9) preparations in which proteolytic activity was inhibited with phenylmethanesulfonyl fluoride followed, after washing, by reductive incorporation of sodium boro[3H]hydride to identify galactose residues exposed on the synaptosomal external surface. Control experiments to demonstrate restriction of labeling to the external surface involved comparing the radioactivity in synaptoplasmic, soluble polypeptides isolated after labeled, isolated synaptoplasm and examining incorporation into fractions incubated without enzymes. Intactness of the synaptic plasma membrane after labeling was shown by trypsin digestion studies. Polypeptides were separated on sodium dodecyl sulfate polyacrylamide gels and were detected by a liquid scintillation counting procedure. Eleven major radioactive peaks were found after galactose oxidase treatment and reduction of isolated synaptic membranes. When intact synaptosomes were labeled, the same components were detected. When isolated synaptic membranes or intact synaptosomes were treated with neuraminidase before galactose oxidase treatment, three additional components were labeled. These results suggest that (a) chick synaptic membranes have a complex mixture of glycoproteins, (b) all major chick synaptic membrane glycoproteins labeled by galactose oxidase have most or all carbohydrate groups exposed at the exterior surface of the synaptosome, (c) all major, externally-disposed polypeptides of these synaptic membranes are glycoproteins.

Animals↗

PubMed1978

Topographic studies of glycoproteins of intact synaptosomes from rat brain cortex.

Glycoproteins in the external surface of intact synaptosomes from rat brain cortex have been studied by oxidation of exposed galactose and galactosamine groups by galactose oxidase followed by reduction with labeled sodium borohydride. Purified synaptosomes were labeled, disrupted by osmotic shock, and the particulate components were fractionated on diatrizoate to give four synaptosomal membrane fractions (A to D) and a mitochondrial pellet (E). Fractions A and B represent highly purified synaptosomal plasma membranes. After separation of their polypeptides by electrophoresis, 4/5 of the label was present in two bands: one about 72 000 and the other between 7800 and 3200 daltons. Seven other bands were labeled to various degrees: 160 000, 96 000, 53 000, 39 000, 34 000, 23 000 and 16 000 daltons. With isolated membranes (which incorporate 5--6 times more label) 4/5 of label was present in polypeptides in three ranges: 160 000--96 000, 70 000--40 000 and 7800--3200. The number of polypeptides that can be labeled by treatment of isolated membranes is very large. In comparison, glycoproteins whose topographical distribution permits interaction with large molecules at the synpatic surface are very limited. It is further suggested that the external synaptosome membrane involves a relatively tight network of interacting molecules that cannot be readily penetrated by large molecules.

Animals↗

PubMed1984

Efflux of gamma-aminobutyric acid from and appearance of free arachidonic acid inside synaptosomes.

When synaptosomes were depolarized in the presence of Ca2+, or when Ca2+ was added to synaptosomes pretreated with Ca2+ ionophore (A23187), free arachidonic acid was clearly increased within synaptosomes, and at the same time an efflux of gamma-aminobutyric acid from synaptosomes was observed. Moreover, when synaptosomes labelled with [14C]arachidonic acid were depolarized in the presence of Ca2+, there was a significant decrease in the radioactivity of the fatty acid of phosphatidylinositol and phosphatidylcholine. Exogenously added arachidonic acid, but not other fatty acids, stimulated the efflux of gamma-aminobutyric acid in the absence of Ca2+. These observations suggest that the release of arachidonic acid from phospholipids is an intrinsic part of the biochemical mechanism that modulates the gamma-aminobutyric acid efflux.

Animals↗

PubMed1994

Increased lipid fluidity in synaptosomes from brains of hyperosmolal rats.

Taurine, a product of sulfur amino acid metabolism, is important in cerebral osmoregulation. To understand the adaptive changes in transport which accompany different hyperosmolal states, we determined lipid composition and fluorescence anisotropy of synaptosomal liposomes from rats with chronic hypernatremic dehydration (CHD), streptozocin-induced (STZ) diabetes, and insulin treated diabetes. Induction of CHD increased serum osmolality, and enhanced in vitro synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Fluorescence anisotropy studies showed that the fluidity of lipids from CHD synaptosomes was higher than control (P < 0.05, n = 3). STZ-diabetes resulted in hyperglycemia, increased serum osmolality, and stimulated synaptosomal taurine uptake (P < 0.01, n = 3, vs. control). Insulin treatment of diabetic rats restored serum osmolality and taurine transport to control values. The fluidity of diabetic rat brain synaptosomal lipids was significantly higher than control (P < 0.05, n = 3); fluidity was normalized by insulin administration to diabetic rats. Total fatty acid, cholesterol, and cholesterol/phospholipid molar ratio of CHD, STZ, and insulin treated diabetic rats were similar to control. However, the ratio of saturated to unsaturated fatty acids was decreased in hyperosmolal states. This suggests that adaptive increases in cerebral taurine transport during hyperosmolality may result from a direct effect on membrane composition that alters fluidity and permits enhanced transmembrane flux of osmoprotective molecules.

Animals↗

PubMed1987

Heterogeneity of presynaptic calcium channels revealed by species differences in the sensitivity of synaptosomal 45Ca entry to omega-conotoxin.

The inhibition of K+-depolarization dependent Ca influx by omega-conotoxin GVIA was compared in the frog, chick, and rat brain synaptosomes. The toxin at concentrations greater than or equal to 0.3 microM completely inhibited Ca entry in the frog and chick preparations, but was only partly effective in blocking Ca influx in the rat brain synaptosomes. In chick synaptosomes the toxin's effect was biphasic: a small component (approximately equal to 15%) of total Ca influx was inhibited by the toxin with high affinity (I50 less than 0.002 microM); a major component (approximately equal to 80%) of Ca influx was inhibited with a moderate affinity (I50 approximately equal to 0.05 microM). In rat brain synaptosomes 40% of Ca influx was inhibited by the toxin with low affinity (I50 approximately equal to 0.3 microM), and 60% of Ca influx was unaffected by the toxin concentration of up to 10 microM. These data suggest a heterogeneity of voltage-sensitive Ca channels in vertebrate brain synaptosomes.

Animals↗

PubMed1982

[3H]Dopamine release by d-amphetamine from striatal synaptosomes of reserpinized rats.

The injection of reserpine, 5 mg/kg i.p. (ipRes), the regimen employed by a majority of investigators, results in synaptosomal and vesicular preparations which are incompletely reserpinized as determined by [3H]dopamine ([3H]DA) accumulation. Reserpine administered by the subcutaneous route, 5 mg/kg (scRes), appears to produce complete reserpinization. Release of [3H]DA by d-amphetamine (Amph) was observed from striatal synaptosomes prepared both from normal rats and those pretreated with reserpine intraperitoneally but not from those injected subcutaneously. In the more completely reserpinized scRes synaptosomes, so little [3H]DA had accumulated that release by Amph was not measurable, indicating that if a labile, reserpine-resistant, extravesicular DA storage pool releasable by Amph is present under these conditions, it must be extremely small. In scRes monoamine oxidase (MAO)-inhibited preparations, Amph released preloaded [3H]DA located in the cytosol in the absence of functional vesicles. Although chromatographic analysis of the superfusate from ipRes striatal synaptosomes showed that significant amounts of preloaded [3H]DA were released by Amph, the level of dihydroxyphenylacetic acid was not increased over controls, indicating that Amph releases only DA and not its metabolite and is also acting as a MAO inhibitor. No [3H]DA could be released by Amph from superfused hyposmotically shocked normal or ipRes synaptosomes, suggesting that an intact membrane is required for Amph-induced release.

Animals↗

PubMed1987

Altered protein phosphorylation in intact rat cortical synaptosomes after in vivo administration of fluphenazine.

Phenothiazines such as fluphenazine are able to inhibit calcium-stimulated protein kinases in vitro in both lysed and intact synaptosomes. In this study protein phosphorylation was assayed in intact synaptosomes isolated from the cerebral cortex of rats treated chronically (21 days, 10 mg/kg, i.p.) or acutely (1 hr, 10 mg/kg, i.p.) with fluphenazine. When intact synaptosomes from chronically treated animals were prelabeled with 32Pi, there were two effects on protein phosphorylation: an increase in the basal labeling of many phosphoproteins and a decrease in depolarization-evoked protein phosphorylation. Acute injections had even more pronounced effects, but the direction and nature of the effects were the same. No effects on K+-stimulated calcium entry or on protein phosphatase activity were detected. When lysed synaptosomes from chronically treated animals were labeled in the presence of [gamma-32P]ATP, a small decrease in calmodulin-dependent and cAMP-dependent protein phosphorylation was observed. The results suggest that two different in vivo mechanisms may underlie these effects, and these are discussed. We proposed that intact synaptosomes may be a good model in which to study the in vivo mechanisms of the action of fluphenazine since they appear to retain at least some effects of the drug after subcellular fractionation.

Animals↗

PubMed1987

Stereochemical effects of 3,4-methylenedioxymethamphetamine (MDMA) and related amphetamine derivatives on inhibition of uptake of [3H]monoamines into synaptosomes from different regions of rat brain.

3,4-Methylenedioxymethamphetamine (MDMA) is a recently popularized recreational drug, although some have advocated its psychotherapeutic potential. Since the pharmacology of MDMA is largely uncharacterized, the stereochemical profiles of MDMA and some of its homologs were derived on inhibition of synaptosomal uptake of [3H]monoamines and compared to those of amphetamine and the hallucinogenic phenylisopropylamine 2,5-dimethoxy-4-methylamphetamine (DOM). In contrast to the 5-fold stereoselectivity observed with amphetamine, only the S-(+) enantiomer of MDMA and 3,4-methylenedioxyamphetamine (MDA) inhibited [3H]dopamine uptake into striatal synaptosomes. Neither stereoisomer of the alpha-ethyl homolog of MDMA, N-methyl-1-(1,3-benzodioxol-5-yl)-2-butanamine (MBDB), inhibited [3H]dopamine uptake. The two stereoisomers of amphetamine and the MDMA-related compounds were equipotent in inhibiting [3H]norepinephrine uptake into hypothalamic synaptosomes. Both stereoisomers of MDMA, MDA and MBDB were potent inhibitors of [3H]serotonin uptake into hippocampal synaptosomes, but only S-(+)-amphetamine produced an appreciable inhibition of [3H]serotonin uptake. Neither stereoisomer of DOM inhibited synaptosomal uptake of any [3H]monoamine. These results suggest that MDMA and its homologs may be more closely related to amphetamine rather than to DOM in their biochemical mode of action. The pronounced effects of the methylenedioxy-substituted compounds on [3H]serotonin and [3H]norepinephrine uptake implicate these neurotransmitters in the pharmacological effects of these drugs.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗

PubMed1991

Neurocatin-induced inhibition of monoamine oxidase A in rat brain synaptosomes.

Neurocatin is a small (about 2000 Da) neuroregulator isolated from mammalian brain. Earlier it was shown that addition of nanomolar concentrations of neurocatin to synaptosomes isolated from rat brain increased levels of serotonin and decreased catabolism of serotonin to 5-hydroxyindoleacetic acid (Fernandez-Novoa L and Pastuszko A. Neurosci Lett 122: 83-86, 1991). In the present study, we report that neurocatin addition resulted in a striking inhibition of monoamine oxidase A activity. This inhibition became statistically significant at a neurocatin concentration of approximately 5 nM and was significant at all higher neurocatin concentrations. Neurocatin at approximately 50 nM inhibited monoamine oxidase A activity by about 90%. The inhibitory effect of neurocatin on monoamine oxidase required its incubation with intact synaptosomes since addition after breaking the synaptosomes by hypotonic buffer or lysis by Triton X-100 almost completely blocked the inhibitory effect. Measurements of the kinetic parameters of the enzyme in lysates prepared from synaptosomes incubated with neurocatin showed a decrease in Vmax with no change in Km for the substrate (serotonin) compared to controls. Incubation of the synaptosomes with approximately 25 nM neurocatin resulted in an 80% decrease in the Vmax of monoamine oxidase A. Evidence that neurocatin is a powerful endogenous modulator of monoamine oxidase activity is particularly intriguing. This enzyme plays a major role in catabolism of the biogenic amines and is believed to contribute to several important neurological disorders.

Animals↗

PubMed1995

Biochemical characterization of ethanol actions on dihydropyridine-sensitive calcium channels in brain synaptosomes.

This study was undertaken to investigate the biochemical events underlying the inhibitory action of ethanol on dihydropyridine-sensitive voltage-dependent Ca2+ channels in brain synaptosomes. The binding of radiolabeled dihydropyridine was used to determine functional Ca2+ channels in synaptosomes following exposure to ethanol. No effect on [3H]PN 200-110 binding was found when disrupted synaptosomal membranes were incubated with ethanol concentrations as high as 300 mM, suggesting that ethanol did not interact directly with sites on or near the Ca2+ channels. However, when intact synaptosomes were first incubated with ethanol (100 mM) at 37 degrees and then disrupted, a significant reduction in membrane binding of [3H]PN 200-110 was found. Ethanol incubation of synaptosomes at 0 degree was ineffective. It appears that metabolic processes involving intracellular factors were required in the ethanol action. In examining this possibility, [3H]PN 200-110 binding was activated by incubation of disrupted membranes with MgATP and Ca(2+)-calmodulin, and ethanol was found to inhibit the activation in a concentration-dependent manner (50-200 mM). [3H]PN 200-110 binding to membranes was also activated by incubation with MgATP and cyclic AMP-dependent protein kinase, but this activation was not inhibited by ethanol. These findings are consistent with the interpretation that ethanol acts on Ca2+ channels by inhibiting calmodulin-dependent activation of the channels.

Adenosine Triphosphate↗

PubMed1976

Stimulation of tyrosine hydroxylase activity by cyclic AMP in synaptosomes and in soluble striatal enzyme preparations.

Dibutyryl cyclic AMP (dB-cAMP) elicits a concentration-dependent stimulation of tyrosine hydroxylase activity in the striatal and mesolimbic synaptosomes. The per cent of stimulation is significantly higher in the mesolimbic synaptosomes than in the striatal synaptosomes. dB-cAMP and depolarizing agents (ouabain or veratridine) have an additive effect on synaptosomal tyrosine hydroxylase activity, indicating that they stimulate tyrosine hydroxylase activity by different mechanisms. cAMP does not stimulate soluble striatal tyrosine hydroxylase activity unless it is added in combination with ATP and Mg2+, compounds required for the activity of cAMP-dependent protein kinase. The cAMP elicited per cent stimulation of soluble tyrosine hydroxylase activity is dependent upon the concentration of added protein kinase and upon the pH of the reaction. dB-cAMP has the same effect on the kinetic state of tyrosine hydroxylase in synaptosomes as cAMP on the soluble tyrosine hydroxylase. The nucleotide does not alter the apparent Km for tyrosine, reduces the Km for the pteridine cofactor and increases the Ki for dopamine. Thus, cAMP increases the affinity of tyrosine hydroxylase for the pteridine cofactor and concomitantly decreases the affinity for the end-product inhibition.

Animals↗

PubMed1976

Evidence that the rapid binding of newly accumulated noradrenaline within synaptosomes involves synaptic vesicles.

When rat brain synaptosomes were incubated with [3H]noradrenaline for 1 min and then exposed to osmotic shock, only about 20% of the newly accumulated [3H]noradrenaline was released. It would appear that most, but possibly not all of the newly accumulated [3H]noradrenaline is rapidly bound to some particulate cytoplasmic constituent within the synaptosome. [3H]Dopamine and [3H]5-hydroxytryptamine were also rapidly bound within synaptosomes but [3H]glycine and [3H]gamma-aminobutyric acid were not. Reserpinization (5 mg/kg, i.p., 24 h before preparation) only slightly reduced the initial rate of [3H]noradrenaline uptake by synaptosomes. However, when reserpinized synaptosomes were osmotically shocked, most of the newly accumulated radioactivity was released; this radioactivity was identified chromatographically as [3H]noradrenaline. On the basis of the findings with reserpinized preparations, it seems likely that (1) the rapid intrasynaptosomal binding involves synaptic vesicles and (2) the neuronal membrane transport system itself may be capable of driving the uptake of noradrenaline by nerve-terminals. The rapid vesicular binding observed may not be essential for the accumulation of the amine by presynaptic terminals during brief exposures.

Animals↗

PubMed1977

Serotonergic afferents to the dorsal raphe nucleus: evdience from HRP and synaptosomal uptake studies.

Afferent connections of the serotonin (5-HT)-containing dorsal raphe nucleus were investigated in the rat utilizing the horseradish peroxidase (HRP) retrograde cell labeling technique. Small quantities (0.1-0.5 mul) of HRP solutions were infused into the dorsal raphe, and the brains were examined 19-72 h later for retrograde transport of the enzyme. Intrinsic connections within the dorsal raphe nucleus were revealed by this mapping technique, as was an input to the dorsal raphe from another serotonergic cell group, the median raphe nucleus. Little evidence was found for projections from other, more remote, brain sites. A serotonergic innervation of the dorsal raphe was also demonstrated by the presence of high affinity uptake of [3H]5-HT (Km=0.17 muM) into synaptosomal suspensions of the dorsal raphe nucleus. Synaptosomal uptake of [3H]5-HT was blocked by selective destruction of serotonergic axon terminals induced by the intraventricular injection of 200 mug of 5,7-dihydroxytryptamine following desipramine HCl pretreatment, but not by destruction of catecholaminergic axon terminals induced by intraventricularly injected 6-hydroxydopamine (2 X 250 mug). The uptake of [3H]-5-HT by synaptosomes of the dorsal raphe was comparable to that of striatal and hypothalamic synaptosomes, and markedly greater than that of synaptosomes from the cerebellum or nearby dorsal central gray or midbrain reticular formation, indicating the presence of a relatively dense serotonergic innervation. These data together indicate that neurons in the dorsal raphe nucleus receive a prominent serotonergic input that is derived, at least in part, from other neurons within the dorsal nucleus and from a neighboring raphe nucleus.

5,6-Dihydroxytryptamine↗

PubMed1980

Release of synaptosomal dopamine formed from tyrosine and L-DOPA.

The present report compares the synaptosomal release of [3H]dopamine, continuously forming from [3H]DOPA, with that of [14C]dopamine, forming from [14C]tyrosine as a marker of dopaminergic nerve endings. For the purpose of the comparison, synaptosomal (P2) preparations from rat caudate nuclei were incubated with L-[3H]DOPA and [14C]tyrosine for 10 min and the particulates were rapidly separated from the medium postincubation. The separated fractions were analyzed for the level of double labelled (14C/3H) dopamine and the synaptosomal content of the labelled substrates. Of the total labelled dopamine formed, the fraction that was present in the medium, following the synaptosomal release, was determined. Tested were the release enhancing effects of various additions which included several known dopaminergic agents, serotonin and 5-hydroxytryptophan. The data show that the addition of dopamine to the incubation mixture to either 0.5 or 1.0 muM concentration markedly enhanced the release of labelled dopamine. Serotonin when added to 5.0 muM concentration also raised the medium content of labelled dopamine but it was ineffective at 1.0 muM. 5-Hydroxytryptophan, 1.0 or 5.0 muM, had no effect. For the comparison of the release enhancing effects of an addition on [14C]dopamine and [3H]dopamine, the corresponding release indices (release index = medium/total ratio of labelled dopamine in the presence of an addition divided by the same ratio in control (no addition) sample) were determined. The data indicate that the index of [14C]dopamine did not differ significantly from that of [3H]dopamine following the addition of either dopamine, serotonin or 5-hydroxytryptophan at any of the concentrations tested. A similar lack of difference between the index of [14C]dopamine and that of [3H]dopamine was observed following the addition of reserpine (1.8 muM), although a considerable enhancement of labelled dopamine release occurred. The addition of either amphetamine (9.1 muM) or amfonelic acid (9.1 muM) also enhanced labelled dopamine release but in their presence the index of [3H]dopamine was significantly higher than that of [14C]dopamine. Amfonelic acid preferentially raised the [3H]dopamine index at the lowest concentration of 0.91 muM that we have tested and also after only 5 min of incubation; coaddition of reserpine increased the [14C]dopamine release, thus abolishing the preferential effect of amfonelic acid on [3H]dopamine release, thus abolishing the preferential effect of amfonelic acid on [3H]dopamine. When the incubation was performed without an addition (control sample), no difference (NS) was observed between the particulate to medium distribution of [14C]dopamine and that of [3H]dopamine after either 5, 10 or 15 min. The results suggest that (a) dopamine synaptosomally formed from L-DOPA may exist in a pool distinct from that dopamine arising from tyrosine hydroxylation and (b) the observed dopamine compartmentation may be due to some mechanism distinct from any possible participation of serotoninergic particles...

Animals↗

PubMed1982

Plasminogen activator is enriched in the synaptosomal plasma membranes.

The intracellular localization of the serine protease plasminogen activator was analyzed in homogenates of bovine brain cortex using differential fractionation procedures. The distribution of the enzyme was clearly different from that of cytosol and mitochondrial markers, and was similar to that of plasma membrane proteins and of the muscarinic acetylcholine receptor, which is a specific marker for the synaptic membrane. The specific activity of plasminogen activator was increased in fractions enriched in intact synaptosomes. Most of the enzyme in intact synaptosomes was found to be firmly associated with the synaptosomal membrane, and could be solubilized by high concentrations of salt or by non-ionic detergent. Purified synaptic vesicles, however, did not contain large amounts of plasminogen activator. Bovine brain synaptosomes were shown to contain two species of the enzyme, having apparent molecular weights of 80,000 and 55,000. The presence of plasminogen activator in the synaptosomal membrane may indicate its possible involvement in the functioning of nerve terminals.

Animals↗

PubMed1984

Preferential uptake of norepinephrine into dopaminergic terminals of a synaptosomal preparation from rat cerebral cortex.

In a synaptosomal preparation from male rat cerebral cortex only 34% of total norepinephrine (NE) uptake could be inhibited by nanomolar concentrations of desmethylimipramine (DMI) with an apparent IC50 value of 0.37 nM. The residual uptake was efficiently inhibited by micromolar concentrations of DMI (IC50 = 4.0 microM). In synaptosomes from the hypothalamus, 74% of total NE uptake could be blocked by DMI with an IC50 of 0.1 nM whereas in synaptosomes from the striatum the IC50 for DMI inhibition was 3.8 microM. It is concluded that in synaptosomes from rat cerebral cortex only 34%, and in synaptosomes from the hypothalamus 74% of total NE are taken up by noradrenergic nerve terminals whereas the residual NE uptake occurs in dopaminergic nerve endings.

Animals↗

PubMed1984

Calcium uptake related to K+-depolarization and Na+/Ca2+ exchange in sheep brain synaptosomes.

The uptake of Ca2+ by synaptosomes induced by K+-depolarization and by Na+/Ca2+ exchange was studied in synaptosomes in which the internal Na+ and K+ contents were varied by prolonged incubation at 30 degrees C or by inhibiting the Na+, K+-ATPase with 1 mM ouabain. Increased Na+ content of the synaptosomes is associated with an increase in Ca2+ uptake when the synaptosomes are placed in depolarizing K+ media. Furthermore, reduction in the [Na+]o, when the [K+]o is increased, in substitution for [Na+]o, to depolarize the membrane, further increases the Ca2+ uptake. Under these conditions, Ca2+ entry probably occurs through voltage-sensitive channels and through the Na+/Ca2+ exchanger. Destruction of the Na+ gradient by monensin, or preloading the synaptosomes with K+, completely inhibits the Ca2+ uptake in a K+-depolarizing medium. It is shown that if the Na+ gradient is maintained constant during K+-depolarization, the Ca2+ uptake is very low and that most of the Ca2+ uptake is correlated with the Na+ gradient. Evidence is presented that K+ may stimulate the Na+/Ca2+ exchange mechanism. Furthermore, divalent cations, Mg2+, Mn2+ and Zn2+, known to block Ca2+ channels, also inhibit Na+/Ca2+ exchange.

Animals↗

PubMed1985

Opioid peptides increase calcium uptake by synaptosomes from brain regions.

The fast-phase calcium uptake by depolarized hippocampal synaptosomes was increased significantly following treatment with 10 nM or 10 microM D-Ala2,D-Leu5-enkephalin (DADLE). No significant changes of calcium uptake by depolarized cortical or striatal synaptosomes were observed for 10 nM or 10 microM treatment with this enkephalin analog. Dynorphin 1-17 analog at 10 nM produces a significant increase in calcium uptake by depolarized striatal synaptosomes. beta-Endorphin and the dynorphin 1-13 fragment analog (10 nM) caused no significant change in the calcium uptake by depolarized synaptosomes from any of the three brain regions. However, calcium uptake by non-depolarized striatal and cortical synaptosomes was increased significantly in the presence of 10 nM beta-endorphin and DADLE. Opioid peptide action on neural calcium uptake is complex and appears to vary somewhat from one brain region to another.

Animals↗