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PubMed2003

[Effect of paraoxon and chlorpyrifos on the nicotinic autoreceptor function in rat cortical synaptosomes].

OBJECTIVE: To explore the effect of organophosphorus insecticides (OPs) on the nicotinic autoreceptor function (NAF) in rat cortical synaptosomes and to understand alternative target of the OPs for human and other animals. METHODS: In vitro experiment, synaptosomes from the rats were incubated with [(3)H] choline and then superfused with physiological buffer. The [(3)H] acetylcholine release from the synaptosomes after the addition of paraoxon or chlorpyrifos to the superfusion system was recorded and the changes of NAF were calculated. In vivo experiment, NAF and acetylcholinesterase (AChE) activity in the cortical synaptosomes in the adult rats dosed with chlorpyrifos were also determined 96 h after OPs treatment. RESULTS: Paraoxon caused slight effect on NAF (average inhibition rate: < 23%) while chlorpyrifos oxon caused > 100% of inhibition on NAF in vitro. Chlorpyrifos markedly reduced NAF by 66% 96 h after treatment and inhibited the AChE activity by 91% in vivo. CONCLUSION: The OPs may have different effects on the NAF of rat cortical synaptosomes while chlorpyrifos may certainly inhibit the NAF in cortical synaptosomes of adult rats.

Acetylcholine↗

PubMedDate not supplied

[Effect of carbacholine and serotonin on the ATPase activity in synaptosomes of the projection and association areas of the feline cerebral cortex].

Na, K-ATPase and Mg-ATPase activities were measured in the synaptosomes of the temporal auditory projection area and the frontal association area. Moreover, the effects of carbacholine and serotonin on those activities were investigated. Na, K-ATPase activity in the synaptosomes of the association area was shown to be reliably higher that in the synaptosomes of the projection area (11.02 +/- 0.45 vs 8.40 +/- 0.55 microM Pi/mg of protein hr; P less than 0.05). Mg-ATPase activity was higher in the second case as compared to the first one (11.40 +/- 0.38 vs 9.04 +/- 0.35; p less than 0.05). Carbacholine and serotonin (10(-8)-10(-3) M) were found to induce equal inhibition of Na, K-ATPase activity in the synaptosomes of both cortices (1 max = 25-30%, 1C50 = 0.2-0.3 microM) which is blocked respectively with atropine (10(-6) M) and methysergide (10(-6) M) and enhanced in presence of GTP (5.10(-5) M). The enzyme activity is also inhibited by the non-hydrolysable guanine nucleotide, GTP gamma S (10(-8)-10(-4) M), in the absence of the antagonists (1 max = 35-40%, 1 C50 = 0.02 microM). In the methysergide-containing medium serotonin exerts a dose-dependent stimulatory effect on Na, K-ATPase which is more pronounced in the synaptosomes of the association area (A max = 25%, A C50 = 0.05 microM). Mg-ATPase activity of membrane preparations is liable to be stimulated by both serotonin and carbacholine, stimulation being more pronounced in the synaptosomes of the association cortex as well (A max = 35%, A C50 = 0.2-0.3 microM). This effect is insensitive either to the antagonists of the corresponding receptors or to GTP. GTP gamma S does not cause alterations in the enzymatic activity. Na, K-ATPase is suggested to be coupled to muscarine and serotonin receptors in the synaptic membranes of both projection and association cortical areas via a GTP-binding protein. At the same time, the agonists of receptors mentioned above are presumably also capable to effect Mg-ATPase activity by the receptor-independent way.

Animals↗

PubMed1990

Higher environmental temperature-induced change in synaptosomal (Na(+)-K+)-ATPase activity of mammalian brain regions.

Exposure of adult male Albino rats to higher environmental temperature (HET) at 35 degrees for 2-12 h or at 45 degrees for 1-2 h decreases hypothalamic synaptosomal (NA(+)-K+)ATPase activity. Synaptosomal (Na(+)-K+)-ATPase activity in (a) CX of rats exposed to 35 degrees for 12 h, (b) CX and PM of rats exposed to 45 degrees for 1-2 h and also (c) in CS of rats exposed to 45 degrees for 2 h are inhibited. (Na(+)-K+)-ATPase activity of synaptosomes prepared from normal rat brain regions incubated at 39 degrees-43 degrees for 0.5-1 h decreased significantly in H and such inhibition was also observed in other brain regions (CX, CS and PM) after incubation of the tissue slices at 41 degrees-43 degrees for 0.5-1 h. Lineweaver-Burk plots indicate that (a) in vivo and in vitro HET-induced inhibition of brain regional synaptosomal (Na(+)-K+)-ATPase is coupled with a decrease in Vmax without any change in Km, (b) very high temperature (under in vitro condition) causes a decrease in Vmax with an increase of Km irrespective of the brain regions. Arrhenius plots show that there is a decrease in transition temperature (TT) in H of rats exposed to either 35 degrees or 45 degrees, whereas such decrease in TT of PM and CX regions are only observed after exposure at 45 degrees. These results suggest that heat exposure increases the lipid fluidity of synaptosomal membrane which may cause the conformational change of the membrane protein and hence inhibit the activity of synaptosomal (Na(+)-K+)-ATPase of brain regions.

Animals↗

PubMedDate not supplied

[Calcium permeability of synaptosomes induced by alpha-latrotoxin].

The paper deals with characteristics of ionic alpha-latrotoxin-induced permeability of rat brain synaptosomes. It has been shown that the addition of alpha-latrotoxin to synaptosomes in the Ca2+-containing media resulted in an extensive and rapid uptake of 45Ca2+ in synaptosomes. alpha -Latrotoxin was not able to enhance the 22Na+ and 86Rb+ uptake or efflux in the Ca2+-containing and Ca2+- and Mg2+-free media. The dye di-O-C3 was used to monitor the membrane potential changes as a consequence of alpha-latrotoxin treatment of synaptosomes. It has been found that alpha-latrotoxin increased synaptosomal fluorescence in the Ca2+-containing media, but failed to induce any increase of fluorescence in Ca2+- and Mg2+-free media. It has been also shown that the calcium uptake induced by alpha-latrotoxin depends on free calcium concentration in synaptosomes. Toxin-induced calcium flows are shown to be of the vector character.

Animals↗

PubMed1989

Aplysia synaptosomes. II. Release of transmitters.

A subcellular fraction (P3) from Aplysia is enriched in synaptosomes (Chin et al., 1988) and is capable of accumulating 5-HT and choline. At an external 3H-5-HT concentration of 1.8 microM, the P3 fraction took up 0.12 nmol/mg protein in 30 min. Uptake was dependent on external Na+. Electron microscopic autoradiography showed that much of the accumulated 3H-5-HT is localized to synaptosomes. At 0.5 microM 3H-choline, P3 took up 0.11 nmol/mg protein in 30 min and converted 40% to 3H-ACh. This synaptosomal fraction was also capable of releasing transmitter. After 3H-5-HT or 3H-choline was taken up, P3 released about 5% of the total radioactive transmitter in a Ca2+-dependent manner during a 30 sec exposure to a depolarizing concentration of K+ (100 mM). Identified, prelabeled synaptosomes were prepared by injecting 3H-choline into the large cholinergic neuron L10. The abdominal ganglia containing the injected cells were then fractionated, yielding synaptosomes containing radioactivity derived from L10. After this synaptosomal fraction was exposed to high K+, 2% of the radioactivity was released in a Ca2+-dependent manner. This release was completely blocked by 0.1 mM histamine, a modulatory transmitter that has previously been shown to cause presynaptic inhibition in L10.

Acetylcholine↗

PubMed1985

Calcium channels in rat brain synaptosomes: identification and pharmacological characterization. High affinity blockade by organic Ca2+ channel blockers.

Rat brain synaptosomes are shown to contain functional voltage-sensitive Ca2+ channels that are inhibited by organic Ca2+ channel blockers. Depolarization of synaptosomes with high K+ stimulates uptake of 45Ca2+ which is biphasic in its time course. Replacement of external Na+ with choline eliminates the slower phase of depolarization-stimulated Ca2+ uptake, leaving only a rapid uptake process which terminates within 1 sec. This rapid, tetrodotoxin-insensitive Ca2+ uptake can be inactivated by prior depolarization of the synaptosomes. Depolarization has no effect on the rate of synatptosomal 22Na+ efflux. These results are interpreted as ruling out Na+/Ca2+ exchange as a mediator of the rapid phase of depolarization-stimulated Ca2+ uptake. A portion (30 to 50%) of the rapid phase of depolarization-stimulated Ca2+ uptake is inhibited by nitrendipine, as is depolarization-stimulated [3H]norepinephrine release from synaptosomes. In external Na+, the inhibition constant (Kapp) for nitrendipine inhibition of Ca2+ uptake is 56 nM. The potency of nitrendipine is increased in the absence of external Na+ (Kapp = 1.7 nM), such that inhibition correlates more closely with the equilibrium dissociation constant for [3H] nitrendipine binding to synaptosomes (Kd = 0.35 nM). Other organic channel blockers (nifedipine, verapamil, D600, and dilitiazem) inhibit the rapid Ca2+ uptake. The potencies of all Ca2+ channel blockers tested by us are in reasonable agreement with their potencies, observed in other laboratories, as blockers of Ca2+ channels in smooth and cardiac muscle. These data demonstrate the existence of active voltage-sensitive Ca2+ channels in synaptosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Cellular mechanisms underlying the increase in cytosolic free calcium concentration induced by methylmercury in cerebrocortical synaptosomes from guinea pig.

Neurotoxic mechanisms of methylmercury (Met-Hg) on presynaptic nerve terminals were studied using the synaptosomes from the cerebral cortex of guinea pig as a model. Cytosolic free calcium [Ca++)c was determined using intrasynaptically trapped fluorescence indicator, fura-2; the plasma membrane potential (delta Up) by measuring the diffusion potential of 86Rb+ and the mitochondrial membrane potential was monitored using the safranine method. Synaptosomal respiration, glycolysis and concentrations of ATP and ADP in the presence and absence of Met-Hg also were quantified. Met-Hg increased synaptosomal [Ca++]c by two distinctive mechanisms. Moderate elevation of [Ca++]c by 127 nM was observed at 30 microM Met-Hg, at which concentration synaptosomal respiration was inhibited completely, leading to partial depolarization of mitochondria. A 3-fold activation of anaerobic glycolysis upon inhibition of respiration was insufficient to sustain terminal energy levels. The delta Up did not depolarize significantly from the resting potential of--67 mV. Thus, the rise in [Ca++]c was due to the energy failure of the synaptosomes, which has been caused by Met-Hg. With 100 microM Met-Hg, [Ca++]c increased extensively by 882 nM. Upon addition of 100 microM Met-Hg the delta Up depolarized instantly dropping 36 mV within 1 min. Synaptosomes were severely energy-deprived, because anaerobic glycolysis was inhibited by 90% from the aerobic level and mitochondrial membrane potential dropped below the limit that could be detected by the safranine method. The proportion of fura-2 signal quenching by Mn++ also increased, indicating that the plasma membrane had become leaky. Thus, at high concentrations of Met-Hg, the rise in [Ca++]c was ascribed to increased ionic permeability of the plasma membrane. The contribution of presynaptic energy failure by Met-Hg is discussed as a possible biochemical mechanism underlying the neurotoxicity of organic mercury.

Animals↗

PubMedDate not supplied

[Proteolipids of brain myelin and synaptosomes in the frog and hen].

Proteolipid complex of Folch-Lees has been obtained and purified from the myelin and synaptosomes of the brain of the frog Rana temporaria and hen Gallus domesticus. Relative content of this proteolipid and glycolipids in the myelin is almost twice higher, whereas that of phospholipids--1 1/2 times lower than in the synaptosomal membranes of the same animal. Protein content of this complex is higher for myelin than for synaptosomal membranes; opposite relation was found with respect to phospholipid content. Within this complex, lipids are presented mainly by phospholipids, especially by acid ones which amount to 30-60%. Proteolipid complexes fro the myelin and synaptosomes differ from each other by their lipid component. Myelin proteolipid complex contains mainly phosphatidylserine and phosphatid acid, whereas synaptosomal one--phosphatidylserine and diphosphatediglycerol. No significant differences were found in fatty acid composition of phospholipids from proteolipid complex from myelin and synaptosomes as compared to this composition in the initial membranes.

Animals↗

PubMed1986

[Mechanism of the stabilization of synaptosomes with alpha-tocopherol during activation of lipid peroxidation].

Using the fluorescent probe technique, it was shown that activation of lipid peroxidation decreases the value of transmembrane potential of rat brain synaptosomes. Depolarization of synaptosomes may be due to the impairment of the "barrier" properties of synaptosomal membranes and the decrease in Na,K-ATPase activity. alpha-Tocopherol and its model derivative devoid of the phytol chain--2,2,5,7,8-pentamethyl-6-oxychromanol--stabilize the transmembrane potential value during inhibition of lipid peroxidation. alpha-Tocopherol acetate causes no stabilizing or inhibiting effects. Unlike 2,2,5,7,8-pentamethyl-6-oxychromanol, alpha-tocopherol exerts a structuralizing action which manifests itself in the stabilization of the synaptosomal membrane potential during incomplete inhibition of lipid peroxidation. The previously established ability of alpha-tocopherol to protect synaptosomes from the damaging action of phospholipases and the experimental results of this work permit to regard vitamin E as a universal stabilizer of brain synaptosomal membranes.

Animals↗

PubMed1986

Affinity fractionation and characterization of chick brain synaptosomes.

Chick brain synaptosomes were fractionated by affinity chromatography on concanavalin A-Sepharose. Three subfractions were obtained. One, designated UBF, was not bound to the affinity adsorbent and represented 36% of the total synaptosomal protein treated with the beads. A second fraction, designated BF1, adhered to concanavalin A-Sepharose exclusively through its carbohydrate recognition site. The third fraction, called BF2, bound to the beads through hydrophobic interactions and represented about 20% of the total synaptosomal protein. About 20% of the total synaptosomal protein was found to be retarded on three ligand-less gels, with potential for only hydrophobic interactions. This binding can be reversed, however, by ethylene glycol, a result indicating hydrophobic binding sites on the synaptosomes. Enzyme marker studies and electron microscopy showed differences between UBF, BF1, and BF2, mainly with respect to mitochondrial contamination. Binding studies with [3H]-Con A show the absence of Con A-specific carbohydrates from the surface of UBF or BF2. As expected strong and specific binding between [3H]-Con A and [3H] BF1 was observed. These findings are discussed in relation to a model for the interior working of the synaptosomes.

Absorption↗

PubMed1986

Effect of early and late postnatal hypoxia on subcellular synaptosomal fractions from cerebral cortex of rats. I. An electron-microscopical and biochemical study.

Synaptosomal fractions of brain cortex of rats exposed to moderate intermittent hypobaric hypoxic conditions during the first or second decade of the postnatal life were investigated electron microscopically one day or up to one week after the hypoxia experiment. Mitochondria and synaptosomes with impaired morphology were observed to occur more frequently in fractions obtained from hypoxic animals. Synaptosomes showed lesions of the outer membrane and loss of the synaptoplasmatic content, or condensation of the synaptosomal content with increasing electron density, deformation of the synaptosomes in size and shape, disappearance of structural details, degeneration of intrasynaptosomal mitochondria in form of strong condensation and, finally, formation of intrasynaptosomal vacuoles with dense core inclusions. The mitochondrial reaction was characterized by two antagonistic configurations: condensation of the matrix with secondary enlargement of the intracistal spaces and of the outer compartment and, finally, the decay of the matrix condensate in several crumbs. On the other hand, swelling of the matrix with strong enlargement of the whole mitochondrium, later defects in the outer membrane and the degeneration into empty mitochondrial ghosts, appearing in the upper fractions. Some characteristic marker enzymes were tested in the fractions. The results hint at an elevated vulnerability of synaptosomes obtained from animals exposed to postnatal hypoxia, as indicated by the lowered quotient of LDH activities after and before addition of Triton X-100. Furthermore, there are clues to a decrease in the number of synaptic connections within the cortex of hypoxia exposed animals, as is concluded from the diminished AChE activity in the subcellular fractions of these animals. However, no different effect of early or late postnatal hypoxia exposition was evident in the biochemical parameters.

Acetylcholinesterase↗

PubMed1986

[Activation of calcium transport in synaptosomes by phosphatidylinositol-specific phospholipase C].

The isotope labeling method was used to study the influence of phospholipases C of different origin and specificity on Ca2+ accumulation in rat brain synaptosomes. It was found that phospholipases C specific to phosphatidylinositides (PI) stimulate Ca2+ transport into synaptosomes, while non-specific phospholipase C, which hydrolyzes different membrane lipid fractions, decreases the Ca2+ content in synaptosomes. It is supposed that the stimulating effect of PI-specific phospholipases C is determined by the activation of PI metabolism, which results in an increase in the content of some PI metabolism products serving as Ca2+ ionophores in synaptosomal membranes. The inhibition of Ca2+ uptake by synaptosomes treated with non-specific phospholipase C is thought to result from partial disruption of synaptosomal membranes.

Animals↗

PubMed1985

Effects of apomorphine enantiomers and of lisuride on 3,4-dihydroxyphenylalanine production in striatal synaptosomes.

The effects of lisuride and of the R(-)- and S(+)-enantiomers of apomorphine were examined on 3,4-dihydroxyphenylalanine (DOPA) production by striatal synaptosomes and by crude, soluble striatal tyrosine hydroxylase. Due to their catechol structure, the enantiomers were almost equally effective in blocking soluble tyrosine hydroxylase (EC 1.14.16.2) (IC50 = 470 and 890 nM for R(-)- and S(+)-apomorphine, respectively), provided incubations were performed at pH 7.2 with 1 mM tetrahydrobiopterin as cofactor. The enantiomers were similarly effective in blocking synaptosomal DOPA production (IC50 = 410 and 970 nM for R(-)- and S(+)-apomorphine, respectively). As S(+)-apomorphine but not R(-)-apomorphine is considered to be a dopamine antagonist, these results support the assumption that the block of synaptosomal DOPA production by both apomorphine enantiomers is due to a direct inhibition of tyrosine hydroxylase. Lisuride at high concentrations (10-100 microM) blocked DOPA production in striatal synaptosomes; simultaneously, intrasynaptosomal dopamine was depleted. These data support the assumption that lisuride inhibits DOPA production indirectly, similar to reserpine. In accordance with this assumption, lisuride was without effect on DOPA production in dopamine-depleted synaptosomes. These results demonstrate that inhibition of synaptosomal DOPA production by at least some dopamine agonists may be explained by direct inhibitory effects on tyrosine hydroxylase.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

[Tryptophan-5-hydroxylase activity in the rabbit brain synaptosomes at different times after the single administration of the opioid peptide Tyr-D-Ala-Gly-Phe-NH2].

The activity of the key enzyme of serotonin biosynthesis--tryptophan-5-hydroxylase (T-5-H) was investigated in the synaptosomes of the motor cortex and caudate nucleus of the rabbit brain 30 min or 5 days after single injection of opioid tetrapeptidamide Tyr-D-Ala-Gly-Phe-NH2 (TPA). TPA was injected subcutaneously at a dose of 500 micrograms/kg of rabbit body weight. T-5-H activity in caudate nucleus synaptosomes was two times higher than that of the motor cortex synaptosomes and accounted for 159.67 and 80.84 pmoles of formed 5-hydroxytryptophan/mg protein per hour. 30 min after single injection of TPA the enzyme activity in the synaptosomes of the motor cortex and caudate nucleus decreased by 64.0 and 43.0%, respectively. 5 days following single TPA injection T-5-H activity in the motor cortex synaptosomes increased by 68.4% and in caudate nucleus synaptosomes decreased by 35.6%. Thus, it was established that TPA displayed a pronounced effect on T-5-H activity. The delayed effect of opioid TPA on T-5-H activity was discovered which was manifested on day 5 after the single injection. Possible mechanisms of TPA effect on T-5-H are discussed.

Animals↗

PubMed1981

Membrane potential of olfactory bulb synaptosomal fractions: characterization with the lipophilic cation tetraphenylphosphonium.

The membrane potential of olfactory bulb synaptosomal fractions was monitored with the lipophilic cation tetraphenylphosphonium (TPP+), which has been reported to distribute across membranes according to the Nernst equation. The properties of the synaptosomal membrane potential as monitored with TPP+ were similar to those reported for neural tissues using other measurement techniques. There is an electrical potential (delta psi) of -64 and -77 mV in the P1 and P2 synaptosomal fractions, respectively. This potential is due primarily to the K+ diffusion gradient across the synaptosomal membrane. The influence of ouabain on TPP+ accumulation indicates that the (Na+,K+)-ATPase electrogenicity contributes about -20 mV to the resting synaptosomal membrane potential. Veratridine induced a decline in TPP+ accumulation which was blocked by tetrodotoxin or by the omission of Na+ from the medium. A significant mitochondrial contribution to TPP+ accumulation, which varied as a complex function of TPP+ concentration in the medium in a manner indicating that TPP+ interfered with the maintenance of mitochondrial potential, was observed. This mitochondrial contribution could be eliminated by performing the experiments anaerobically in the presence of oligomycin. The results are discussed with relation to the future possible use of TPP+ for delta psi measurements in synaptosomal preparations.

Animals↗

PubMed1980

Stimulation and inhibition of synaptosome ATPases by noradrenaline. The involvement of cytoplasmic factor.

The activity of Na+, K+-ATPase was determined in synaptosomes and in pellets, (containing membranes, mitochondria and vesicles) and cytoplasm prepared from synaptosomes from rat cerebral cortex. The activity of the pellets was more than two fold higher than that of the synaptosomes or of their components and adding back the cytoplasm reduced the activity of the pellets. Noradrenaline did not affect the activity of the pellets but increased that of the synaptosomes in a dose-dependent fashion. It inhibited the activity of the membranes. Results indicate that synaptosomal Na+, K+-ATPase activity is low because of a factor in the cytoplasm and this factor is not present in synaptosome pellets. NA antagonises the activity of the factor.

Animals↗

PubMed1982

Effect of delta9-tetrahydrocannabinol on the synthesis of dopamine and norepinephrine in mouse brain synaptosomes.

The effects of delta 9-tetrahydrocannabinol (THC) on the conversion of [3H]tyrosine (TYR) to [3H]dopamine (DA) and [3H]norepinephrine (NE) by mouse brain synaptosomes were studied. The active uptake of TYR and its conversion to DA and NE were found to be concentrated in a synaptosomal subfraction prepared by using differential and density gradient centrifugation. Therefore, drug studies were performed by using the less pure P2 fraction. THC was administered in vitro by using a polyvinylpyrrolidone vehicle. DA synthesis was examined both in synaptosomes prepared from whole brain and from corpus striatum. THC produced increases in the conversion of TYR to DA in both preparations. Synthesis was stimulated maximally by 10 microns THC in both preparations. Higher concentrations produced either no further increase (whole brain) or a decrease in the synthesis of DA. NE synthesis was measured in synaptosomes prepared from whole brain and from brainstem. A concentration-dependent biphasic response was observed in both preparations. Peak increases in NE synthesis were observed with a 10 micron concentration of THC in synaptosomes from whole brain and a 3 micro concentration in the brainstem. THC also inhibited the active uptake of TYR into synaptosomes in all preparations studied. The lC50 in whole brain was 12.2 microns. The decrease in precursor uptake may be the cause of the decreased DA and NE synthesis observed at the higher concentrations of THC. The data from these studies suggest that delta 9-THC can have a direct effect upon catecholamine-containing neurons in the brain.

Animals↗

PubMed1984

Accumulation, subcellular localization and release of propranolol from synaptosomes of rat cerebral cortex.

Propranolol is accumulated at several adrenergic neuroeffector junctions after chronic oral administration in the dog, and is released subsequently during sympathetic nerve stimulation. In the present study, the accumulation, subcellular localization and release of propranolol was examined in rat cortical synaptosomes. Synaptosomal propranolol accumulation was rapid and attained equilibrium within 1 min. Propranolol uptake increased in a nonlinear manner with increasing drug concentration in the medium, but could not be fully saturated over the concentration range studied (10(-7) - 10(-3) M). Uptake was unaffected by cocaine or ouabain and showed no stereoselectivity. Subsynaptosomal fractionation of propranolol-loaded synaptosomes revealed that the drug was concentrated principally in fractions enriched in synaptic plasma membranes and synaptic storage vesicles. Exposure of propranolol-loaded synaptosomes to elevated potassium evoked a concentration-dependent increase in propranolol overflow, which was not seen in mitochondrial fractions, myelin fractions or in freeze-thawed synaptosomal preparations. Veratridine was also effective in promoting propranolol overflow in a concentration-dependent manner. The increase in propranolol overflow induced by elevated potassium was significantly reduced, but not completely inhibited, in a calcium-free, ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid-supplemented medium. These results indicate that propranolol may be accumulated by neuronal tissue and stored at sites from which release may occur in response to depolarizing stimuli. The data further suggest that propranolol release in the synaptosome preparation may occur by both calcium-dependent and calcium-independent processes.

Animals↗