Glutathione defense system in various brain structures during starvation]

Distribution of glutathione reductase (GR) and selenium-dependent glutathione peroxidase (GP) activity and the content of selenium in the cytosolic fraction of the brain stem, hypothalamus and different cortical areas of the rat cerebrum in norm and under starvation was investigated. It was shown that GR activity in all investigated structures was approximately identical, but GP activity in various cortical areas was 1.5-2.0 times higher, than that in the mesencephalon and myeloencepalon. During 2-3 days of starvation GR activity changed insignificantly, whereas GP activity varied within wide limits. Under prolonged starvation a significant decrease in the content of selenium and GP activity was observed. The correlation of these changes was more expressed in the hypothalamus. It was assumed that glutathione and enzymes of its metabolism were involved in the regulatory system of redox processes in the nervous tissues in the primary period of starvation.     

Differential modulation of carbachol and trans-ACPD-stimulated phosphoinositide turnover following traumatic brain injury

In the fluid percussion model of traumatic brain injury (TBI), we examined muscarinic and metabotropic glutamate receptor-stimulated polyphosphoinositide (PPI) turnover in rat hippocampus. Moderate injury was obtained by displacement and deformation of the brain within the closed cranial cavity using a fluid percussion device. Carbachol and (±)-1-Aminocyclopentane-trans-1,3.-dicarboxylic acid (trans-ACPD)-stimulated PPI hydrolysis was assayed in hippocampus from injured and sham-injured controls at both 1 hour and 15 days following injury. At 1 hour after TBI, the response to carbachol was enhanced in injured rats by up to 200% but the response to trans-ACPD was diminished by as much as 28%. By contrast, at 15 days after TBI, the response to carbachol was enhanced by 25% and the response to trans-ACPD was enhanced by 73%. The ionotropic glutamate agonists N-methyl-D-aspartate (NMDA), and -amino-3 hydroxy-5-methyl-4-isoxazolepropionate (AMPA), did not increase PPI hydrolysis in either sham or injured rats and injury did not alter basal hydrolysis. Thus, hippocampal muscarinic and metabotropic receptors linked to phospholipase C are differentially altered by TBI.Abbreviations used TBI traumatic brain injury - EAA excitatory amino acids - PPI polyphosphoinositides - IP inositol phosphates - NMDA N-methyl-D-aspartate - AMPA -amino-3-hydroxy-5-methylisoxazole-4-propionate - trans-ACPD (±)-1-Aminocyclopentanetrans-1,3-dicarboxylic acid - LTP long term potentiation     

Arginine-vasopressin V1a receptor inhibition improves neurologic outcomes following an intracerebral hemorrhagic brain injury

Cerebral edema is a devastating consequence of brain injury leading to cerebral blood flow compromise and worsening parenchyma damage. In the present study, we investigated the effects of arginine-vasopressin (AVP) V(1a) receptor inhibition following an intracerebral hemorrhagic (ICH) brain injury in mice and closely assessed the role it played in cerebral edema formation, neurobehavioral functioning, and blood-brain-barrier (BBB) disruption. To support our investigation, SR49059, an AVP V(1a) receptor competitive antagonist, and NC1900, an arginine-vasopressin analogue, were used. Male CD1 mice (n=205) were randomly assigned to the following groups: na?ve, sham, ICH, ICH with SR49059 at 0.5 mg/kg, ICH with SR49059 at 2mg/kg, ICH with NC1900 at 1 ng/kg, ICH with NC1900 at 10 ng/kg, and ICH with a combination of SR49059 at 2 mg/kg and NC1900 at 10 ng/kg. ICH was induced by using the collagenase injection model and treatment was given 1h after surgery. Post assessment was conducted at 6, 12, 24, and 72 h after surgery and included brain water content, neurobehavioral testing, Evans Blue assay, western blotting, and hemoglobin assay. The study found that inhibition of the AVP V(1a) receptor significantly reduced cerebral edema at 24 and 72 h post-ICH injury and improved neurobehavioral function while reducing BBB disruption at 72 h. Western blot analysis demonstrated increased protein expression of aquaporin 4 (AQP4) in vehicle, which was reduced with AVP V(1a) receptor inhibition. Our study suggests that blockage of the AVP V(1a) receptor, is a promising treatment target for improving ICH-induced brain injury. Further studies will be needed to confirm this relationship and determine future clinical direction.     

Influence of atropine and carbachol on the fluorescence of catecholaminergic structures in selected areas of the rat brain.

Using the formaldehyde-fluorescence technique, the authors studied the influence of atropine and carbachol, administered intraventricularly to Wistar rats, on the fluorescence of catecholaminergic structures in 20 areas of the CNS, situated within the range of the 10th-46th frontal plane according to KONIG and KLIPPEL. 1. A confirmation of the antagonistic action of atropine and carbachol was obtained. It was expressed by mutually opposed occurrence of the specific fluorescence of the catecholaminergic structures. 2. In 16 out of 20 studied areas of the CNS, carbachol abolished or considerably weakened the specific fluorescence. In 3 areas it was increased by this drug, and one area proved insensitive. 3. Atropine increased the specific fluorescence in the DA (dopaminergic system) areas, while it had varying effects in the NA (noradrenergic system areas. In some areas of the CNS it increased and in others reduced the specific fluorescence of the catecholaminergic structures. 4. An interference between atropine and carbachol is observed, but it seems that the results of the present experiment speak in favour of an interaction between the catecholamine transmitters and ACh in the particular areas of the CNS under the influence of atropine and carbachol. 5. The authors discuss in detail the reactions of the catecholaminergic structures in the particular areas of the CNS, in which, as compared with the control, an increase or a decrease of the specific fluorescence under the influence of the administered drugs was observed.     

Rapid repletion of brain serotonin in malnourished corn-fed rats following L-tryptophan injection.

The concentration of tryptophan in serum, and the levels of tryptophan, serotonin (5-HT), and 5-hydroxyindole-acetic acid (5-HIAA) in brain are substantially reduced in rats that consume for 6 weeks a diet in which corn is the only source of protein. Single injections of L-tryptophan (25, 50, or 100 mg/kg) cause dose-related increases in brain tryptophan, 5-HT, and 5-HIAA in corn-fed animals. At each dose, brain tryptophan content rises to a proportionately greater extent in corn-fed rats than in well-nourished controls, even though serum tryptophan concentrations attain higher levels in controls. This difference may reflect the greatly reduced serum concentrations in corn-fed rats of other large neutral amino acids that compete with tryptophan for uptake into the brain (tyrosine, phenylalanine, leucine, isoleucine, and valine). However, the substantial decrease in serum albumin levels also diminishes the binding of tryptophan to serum albumin; thus it is not yet possible to state which of these changes is responsible for the much greater increments in brain tryptophan observed in corn-fed rats after tryptophan injection. The fact that tryptophan administration rapidly restores brain 5-hydroxyindole levels in corn-fed animals suggests that the reductions in 5-HT and 5-HIAA levels associated with this type of malnutrition may be largely caused by inadequate availability of substrate.     

Carbachol and histamine stimulation of guanine-nucleotide-dependent phosphoinositide hydrolysis in rat brain cortical membranes.

Guanine nucleotides have been shown to stimulate phosphoinositide breakdown in brain membranes, but no potentiation of such an effect by agonist was demonstrated. We have studied the effect of carbachol and histamine on guanosine 5'-[gamma-thio]triphosphate (GTP[S]) stimulation of inositol phosphates formation in [3H]inositol-labelled rat brain cortical membranes. In this preparation, GTP[S] enhancement of phosphoinositide hydrolysis required the presence of MgATP and low Ca2+ concentration (100 nM). Carbachol potentiation of the GTP[S] effect was only observed when 1 mM-deoxycholate was also added. Under these conditions, stimulated production of [3H]inositol phosphates was linear for at least 15 min, and [3H]inositol bisphosphate [( 3H]IP2) accounted for approx. 80%, whereas the amount of [3H]inositol trisphosphate [( 3H]IP3) was very low. Stimulation by GTP[S] was concentration-dependent (half-maximal effect at 0.86 microM), and its maximal effect (815% over basal) was increased by 1 mM-carbachol (1.9-fold) and -histamine (1.7-fold). Both agonists decreased the slope index of the GTP[S] concentration/effect curve to values lower than unity, suggesting the appearance of some heterogeneity in the population of guanine-nucleotide-binding proteins (G-proteins) involved. The carbachol and histamine effects were also concentration-dependent, and were inhibited by atropine and mepyramine respectively. Fluoroaluminate stimulated phosphoinositide hydrolysis to a higher extent than GTP[S] plus carbachol, and these stimulations were not additive, indicating that the same polyphosphoinositide phospholipase C-coupled G-protein mediates both effects.     

Relative sensitivity of various cell cultures to the thermostable exotoxin of B. thuringiensis]

The "thermostable" B. thuringiensis exotoxin is active on cell cultures of Mammals "in vitro", except on the KB strain from a human tumor. The primary cultures are the most sensitive: first, with monkey kidney cells, the growth is inhibited by 0.1 mg of toxin per ml; next, the young rabbit kidney cells react to 0.25 mg of toxin per ml. The established lines of cells come last: human diploid cells (Lyon 4) and heteroploid cells (BHK21C13), with the same active dose of 1 mg of toxin per ml. No protection is obtained by adding ATP to monkey kidney cells at the same time as the exotoxin.     

Time course for labeling of brain membrane phosphoinositides and other phospholipids after intracerebral injection of [32P]-ATP. Evaluation by an improved HPTLC procedure

An improved two-dimensional HPTLC procedure was developed for separating phospholipids including individual phosphoinositides, phosphatidic acids and plasmalogens. This procedure was used to examine the time course for uptake of label by phospholipids in brain subcellular membranes after intracerebral injection of [gamma-32P]-ATP. There were considerable differences in the phospholipid labeling pattern among different subcellular fractions. In particular, a high proportion of labeled phosphatidylinositol 4,5-bisphosphates and phosphatidic acids was found in the myelin fraction during the initial 4 hr after injection. In other subcellular fractions, labeling of phosphoinositides was maximum at 2 hr, but with prolonged time, poly-phosphoinositides started to show a decline in radioactivity whereas labeling of other phospholipids continued to show a steady increase instead. Results indicate at least two different modes for the uptake of label by brain membrane phospholipids after intracerebral injection of [32P]-ATP.     

Circadian rhythm of glycogen content in various brain structures of Serranus scriba Cuv.

In different brain structures (telencephalon, tectum opticum, rhombencephalon, cerebellum and medulla oblongata) of the teleost Serranus scriba Cuv., the content of glycogen was observed during a 24-h period. A circadian rhythm of brain glycogen concentration was found. The results are discussed with particular reference to the possible relation between catecholamines, cyclic adenine nucleotide and glycogen metabolism in the brain.     

Axonal transport of glycerophospholipids following intracerebral injection of glycerol into substantia nigra or lateral geniculate body

[2-³H]Glycerol was injected into one substantia nigra of adult rats. Incorporation of radioactivity into lipids at the injection site was maximal by 2 hr, after which it declined. Rapidly transported³H-labeled lipids were just beginning to accumulate in the primary projection site, the ipsilateral corpus striatum by 2 hr, as evidenced by 20-fold higher levels of lipid radioactivity in the projection site relative to control regions. However, the bulk of labeled lipid arrived between 6 hr and 3 days postinjection, suggesting either a prolonged period of release of rapidly transported lipids from the nerve cell bodies or a slow rate of transport for the later arriving lipids. Colchicine applied locally to the fibers of this tract blocked the axonal transport of lipids to the striatum almost completely. Choline and ethanolamine phosphoglycerides were the major transported lipids, accounting for approximately 60% and 25%, respectively, of the total. Similar results were obtained in studies of [2-³H]glycerol-labeled lipids synthesized in the lateral geniculate body and transported to the visual cortex. The rapid axonal transport of lipids labeled with [³²P]phosphate (injected simultaneously with [2-³H]glycerol) could also be demonstrated in both tracts. However, in contrast to [2-³H]glycerol, considerable amounts of³²P soluble label were present in the projection sites, and colchicine only partially blocked the accumulation of³²P-labeled lipid. These results demonstrate the relative utility of [2-³H]glycerol as a lipid precursor for examination of axonal transport in intrabrain tracts. Characteristics of lipid axonal transport in these two intrabrain tracts are similar to each other and are also similar to those previously described for retinal ganglion cells, indicating a common requirement for the axonal transport of these membrane constituents to axons and nerve endings in widely divergent CNS tracts.Presented in part at the 11th meeting of the American Society for Neurochemistry, Houston, Texas, March 1980.     

Modulation of dopamine-induced hypermotility following injection of various opioids into the nucleus accumbens

The aim of the present work was to obtain some data on the eventual role of nucleus accumbens in the antidopamine action of some opioids. Classical neuroleptics are known to inhibit the dopamine-elicited hypermotility when injecting them into the nucleus accumbens of rats pretreated with MAO inhibitors. In the present study the effects of some opioids have been examined in this model. The opioids examined were morphine, a mu-selective classical opiate, D-Ala2, Nle5-enkephalin sulphonic acid (ES), a delta selective opioid peptide and D-Met2, Pro5-enkephalinamide (EA), a non-selective opioid peptide. Haloperidol and chlorpromazine have been used for comparison. EA and morphine, especially the former, potently antagonized the dopamine-induced hyperactivity, similarly to haloperidol and chlorpromazine. ES exerted biphasic effect, the initial inhibition was followed by potentiation of the dopamine-elicited excitation. Thus the order of potency was: EA greater than haloperidol approximately equal to morphine greater than chlorpromazine greater than EA. The data indicate that the antidopamine action of opioids might be mediated, at least in part, by mu-receptors in the nucleus accumbens.     

Effect of elimination of visual afferentation on electrical activity of various brain structures

Changes in spontaneous brain electrical activity were studied in experiments on rabbits totally blinded by enucleation befor acquiring vision, and on rabbits with direct vision excluded. Total exclusion of vision causes a sharp decrease in amplitude of electrical potentials in the cortex and subcortex. Depression of activity is greatest in the visual cortex and adjacent regions. Deprivation of direct vision also leads to definite changes in the EEG. The most marked changes are produced by restoration of normal vision. The possible mechanisms of the manifestation of depression in the brain electrical activity of animals with blocked visual function are discussed.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 5, No. 5, pp. 497–501, September–October, 1973.