Effect of ethanol on the concentration of enkephalins in the brain of rats with different levels of alcoholic motivation

Radioimmunoassay was used to measure the content of leu- and met-enkephalins in white random-bred rats divided into groups according to the duration of ethanol anesthesia and the levels of 15% ethanol consumption under the conditions of free choice. The concentration of neuropeptides was determined in the cortex of the large hemispheres, striatum, thalamus, and medulla oblongata. The short-sleeping animals manifested elevated concentration of leu-enkephalin in the cortex and that of met-enkephalin in the striatum, medulla oblongata, and thalamus. Prolonged alcoholization under the conditions of free choice led, in the much-drinking animals, to decreased concentration of leu- and met-enkephalins in the striatum, thalamus and medulla oblongata and to increased concentration of leu-enkephalin in the cortex. The importance of leu- and met-enkephalins in the pathogenesis of chronic experimental alcoholism in rats with different alcoholic motivation is considered.     

Developmental Changes in the NGF Content in the Brain of Young,Growing, Low-Birth-Weight Rats

The NGF content in each region of the brain of four-week-old rats was ranked in the decreasing order of cerebral cortex, hippocampus, cerebellum, midbrain/diencephalon, and pons/medulla ob-longata, and the NGF concentration, in the decreasing order of hippocampus, cerebral cortex, cerebellum, midbrain/diencephalon, and pons/medulla oblongata in both AFD and SFD groups. The NGF content and concentration in the cerebral cortex were about the same value at each age between those in the AFD and SFD groups. Those in the hippocampus were a little higher in the SFD group than in the AFD group at the ages of three and four weeks, unlike those in the other regions, where the values for the cerebellum, midbrain/diencephalon and pons/medulla oblongata tended to be somewhat higher in the AFD group than in the SFD group. The NGF concentrations in the hippocampus and cerebral cortex increased with growth: the concentration in the hippocampus at four weeks of age was about 4-fold of that at one week in the AFD group and about 5.7-fold of that at one week in the SFD group; and likewise the concentration in the cerebral cortex at four weeks of age was about 5.3-fold in the AFD group and about 7-fold in the SFD group. The NGF concentrations in the cerebellum decreased, and those in midbrain/diencephalon and pons/medulla oblongata hardly changed with growth in either AFD or SFD group. From these results NGF may have stronger implications for the neuronal growth in the hippocampus compared with those in the lower brain regions of the SFD rats.     

Metallothionein-I induction by stress in specific brain areas

The distribution of metallothionein-I (MT) in several areas of the brain and its induction by immobilization stress has been studied in the rat. MT content was highest in hippocampus and midbrain and lowest in frontal cortex and pons plus medulla oblongata. Immobilization stress for 18 hours (which was accompanied by food and water deprivation) significantly increased MT levels in the frontal cortex, pons plus medulla oblongata and hypothalamus, but not in midbrain and hippocampus. The effect of stress on MT levels was specific as food and water deprivation along had no significant effect on MT levels in any of the brain areas studied. The effect of stress on MT levels was independent of changes in cytosolic Zn content; this was generally unaffected by stress or food and water deprivation but decreased in pons plus medulla oblongata from stressed rats. The results suggest that MT is induced more significantly in the brain areas that are usually involved in the response of animals to stress.     

Level of delta sleep-inducing peptide (DSIP) in the brain of rats with different alcoholic motivation

Radioimmunoassay was used to measure the content of delta-sleep-inducing peptide (DSIP) in random-bred albino rats divided into groups according to the duration of ethanol anesthesia and the levels of 15% ethanol consumption under free-choice conditions. The concentration of the neuropeptide was assayed in intact brain, in the cortex of large hemispheres, medulla oblongata, thalamus and striatum. The short-sleeping rats manifested a statistically significant lowering of the DSIP content in intact brain homogenates, in the cortex of large hemispheres and striatum. On the contrary, thirty minutes after a single intraperitoneal injection of ethanol in a dose of 1 g/kg the DSIP content in the medulla oblongata, thalamus and striatum was found to be increased. The raising of the ethanol dose up to 2.5 and 4.5 g/kg was followed by a less significant increase in the neuropeptide content. Prolonged chronic alcoholization under free-choice conditions led after 12 months to the reduced DSIP content in the medulla oblongata, thalamus and striatum. The importance of DSIP for the pathogenesis of experimental alcoholism using rats with different levels of alcoholic motivation is discussed.     

Glycolysis in rat brain tissue slices following neonatal head x-irraidation: relation of regional differences to the LDH:GPDH ratio

—Following head X-irradiation (750 r) of 2-day-old rats the aerobic formation of lactate in the presence or absence of chloral was markedly increased in medulla slices but remained unchanged in cerebral cortex and brain stem slices. The ratio of lactate dehydrogenase (EC 1.1.1.27) to glycerolphosphate dehydrogenase (EC 1.1.1.8) was slightly increased in cortex and brain stem but more than doubled in medulla. The relation of the increased aerobic formation of lactate in irradiated medulla to the lactate dehydrogenase:glycerolphosphate dehydrogenase ratio is discussed.     

Aspartate Aminotransferase for Synthesis of Transmitter Glutamate in the Medulla Oblongata: Effect of Aminooxyacetic Acid and 2-Oxoglutarate

The effects of aminooxyacetic acid (AOAA), a transaminase inhibitor, and 2-oxoglutarate, a precursor to glutamate by the activity of aspartate aminotransferase (AAT), on slices of rat medulla oblongata, cerebellum, cerebral cortex, and hippocampus were studied. The slices were superfused and electrically stimulated. There was a Ca2+-dependent stimulus-evoked release of endogenous glutamate, gamma-aminobutyric acid (GABA), and beta-alanine in all regions examined. AOAA (10(-4) and 10(-3) M) decreased the release of glutamate in the medulla oblongata and cerebellum but not in the hippocampus. L-Canaline, a specific inhibitor of ornithine aminotransferase, did not affect the glutamate release in the medulla. 2-Oxoglutarate (10(-3) M) increased the release of glutamate in the medulla oblongata and cerebellum but not in the cerebral cortex and hippocampus. Treatment with AOAA (10(-4) M) almost abolished the activities of AAT in all regions studied. AOAA (10(-4) and 10(-3) M) increased the stimulus-evoked release of GABA in the cerebellum, cerebral cortex, and hippocampus, whereas the stimulus-evoked release of beta-alanine was decreased by this agent in all regions studied. These results suggest the participation of AAT in the synthesis of the transmitter glutamate in the medulla oblongata and cerebellum of the rat.     

Arachidonic acid-induced inhibition of (Na+K+)-stimulated ATPase in the cerebral cortex and medulla oblongata of young and adult rats

The effect of arachidonic acid in 5.10(-4) and 5.10(-5) mol.l-1 concentration (as the Na salt, SIGMA) on ouabain-sensitive ATPase (E. C. 3.6.1.3) activity was studied in the cerebral cortex and medulla oblongata of 5-day-old and adult rats. In adult rats, arachidonic acid significantly inhibited ouabain-sensitive ATPase activity in both the cerebral cortex and the medulla oblongata. In 5-day-old rats, only the higher concentration (5.10(-4) mol.l-1) inhibited the enzyme statistically significantly; use of the lower concentration was not followed by any significant changes in Na+-K+-ATPase activity.     

Developmental plasticity of central noradrenaline neurons after neonatal damage--changes in transmitter functions.

The effects of neonatal 6-hydroxydopamine (6-OH-DA) treatment (systemic administration) on noradrenaline (NA) metabolism, turn over, and receptor characteristics have been investigated in rat brain in the adult stage. This treatment is known to preferentially affect the locus coeruleus (LC) NA system leading to a marked NA denervation in the central cortex and hyperinnervation of NA nerve terminals in the pons and medulla oblongata without influencing the LC perikarya. The main NA metabolite, 3-methoxy-4-hydroxy-phenylglycol (MOPEG) was reduced by about 70% in the cerebral cortex after 6-OH-DA treatment at birth while the endogenous NA was almost completely depleted (-92%). The MOPEG levels were not significantly changed in the pons medulla after 6-OH-DA treatment in contrast to the 60% increase of the endogenous NA concentration. The relative reduction of NA in the cerebral cortex of 6-OH-DA treated rats increased in the cerebral cortex following administration of the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (H44/68) compared to the control, while the H44/68 induced depletion of NA was reduced in the pons medulla after 6-OH-DA. The steady-state level of endogenous NA and the effect of H44/68 were unchanged in the LC perikarya after 6-OH-DA treatment. These results indicate that the NA turn over in remaining NA nerve terminals in the cerebral cortex is increased after 6-OH-DA, while decreased in the pons-medulla, possible related to changes in the activation of presynaptic alpha-adrenoreceptors in both regions. NA-induced formation of cAMP in vitro was found to be markedly increased in the cerebral cortex after 6-OH-DA, whereas no consistent change was observed in the pons medulla. Measurements of alpha- and beta-receptor binding in vitro using radioligand techniques showed an increase of binding sites (20%--50%) for both receptors in the neocortex aster 6-OH-DA, whereas no changes were observed in the pons medulla. The 6-OH-DA induced changes in NA turnover, cAMP generating systems, and receptor density may all represent compensatory processes following the altered development of the NA neurons induced by 6-OH-DA.     

Homocarnosinase activity in the rat brain areas kidneys under different states of hyperbarooxygenation

The homocarnosinase activity in different brain areas and kidneys of the normal rats and under different conditions of hyperbarooxygenation are determined. The highest activity of this enzyme is observed in cerebellum. The high homocarnosinase activity is typical of kidneys as well. The action of oxygen in a dose of 0.425 MPa for 60 min (in the absence of convulsions) increases the homocarnosinase activity in the cerebral hemispheres by 18.6%, in the midbrain by 18.6%, in midbrain and diencephalon--by 56.5%, and in the medulla oblongata--by 40.6%. The homocarnosinase activity in the cerebellum decreases by 16.7%, in kidneys--by 18.5%. At the convulsive stage of oxygen intoxication caused by the effect of 0.7 MPa dose of oxygen the homocarnosinase activity in cerebral hemispheres rises by 158.5%, in the midbrain and diencephalon--by 141.5%, in the medulla oblongata by--161.1%. Under the same conditions homocarnosinase activity in the cerebellum is unchanged as compared with the control.     

Cytochrome Reductase Activities in Rat Brain Microsomes During Development

Abstract: Postnatal developmental alterations of microsomal NADH-cyto-chrome b₅ reductase and NADPH-cytochrome c reductase activities were determined in the brain of rats. The reductase activities increased from a low level in the immature brain to a maximum level at 23 to 30 days of age, and then decreased slightly to a plateau. The periods of the activity increments were in accord with those of the enhancement of microsomal fatty acid elongation. The specific activities of these reductases were high in cerebral hemispheres and medulla oblongata, intermediate in midbrain, and lowest in cerebellum of the four regions of 20-day-old rat brain.     

STEARYL COENZYME A DESATURASE ACTIVITIES IN RAT BRAIN MICROSOMES

—A quantitative assay for the rat brain microsomal stearyl CoA desaturase is described. The method was used to determine the developmental pattern and regional distribution of the desaturase in rat brain. Even though the specific activity of the enzyme decreased to one-third from 8 to 60 days of age, the total activity per brain remained the same. The regional distribution of the activity in adult brain was of the order midbrain > medulla oblongata > cerebral hemispheres > cerebellum, with midbrain activity being about twice as that of the cerebellum.     

Influence of starvation on lactic dehydrogenase activity in the serum and brain of rats of different ages.

The authors investigated the effect of 24 hours' acute deprivation of food and liquids on lactic dehydrogenase (LDH) activity in the serum, cerebral cortex, subcortical formations and medulla oblongata of 6- and 14-day-old and adult rats. Young rats were starved by separating half of a standard litter from the female for 24 hours. LDH activity was determined by means of Sevac-test-LDH (Imuna, Czechoslovakia) and was expressed in I.U./litre serum or 1 kg tissue wet weight. The samples were prepared at 0 degrees C. LDH activity in the various parts of the CNS was measured in the supernatant of homogenates of the above tissues and the greatest possible destruction of the tissues was ensured by freezing and thawing the homogenates prior to centrifugation. The specimens were incubated at 37 degrees C. Extinction was measured on a SPECOL (G.D.R.) apparatus at 505 nm wavelength. We found that 24 hours' deprivation of food and liquids, together with sensory deprivation in the youngest age groups, significantly reduced LDH activity in both the serum and the cerebral cortex of 6-day-old rats. In adult rats, starvation and thirst raised LDH activity, but the only statistically significant increase was in the medulla oblongata. Under our experimental conditions, LDH activity rose during development by 274% in the cerebral cortex, by 233% in subcortical formations and by 173% in the medulla oblongata. The differences betwen these developmental trends are statistically significant.     

Reduction in brain immunoreactive corticotropin-releasing factor (CRF) in spontaneously hypertensive rats

The brain CRF concentration of spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) was examined by rat CRF radioimmunoassay. Anti-CRF serum was developed by immunizing rabbits with synthetic rat CRF. Synthetic rat CRF was also used as tracer and standard. The displacement of 125I-rat CRF by serially diluted extracts of male Wistar rats hypothalamus, thalamus, midbrain, pons, medulla oblongata, cerebral cortex, cerebellum and neurointermediate lobe was parallel to the displacement of synthetic rat CRF. In both WKY and SHR the highest levels of CRF immunoreactivity were shown by the hypothalamus and neuro-intermediate lobe, and considerable CRF immunoreactivity was also detected in other brain regions. The CRF immunoreactivity in the hypothalamus, neurointermediate lobe, midbrain, medulla oblongata and cerebral cortex was significantly reduced in SHR and it may suggest that CRF abnormality may be implicated in the reported abnormalities in the pituitary-adrenal axis, autonomic response and behavior of SHR.     

Homocarnosine content and homocarnosine-carnosine synthetase activity in brain areas of hyperoxic rats

The homocarnosine content and homocarnosine synthetase activity were studied in the brain of rats in normal state and under hyperoxia. The homocarnosine content is higher in phylogenetically old brain areas as compared with that in the cerebral hemispheres. Its nonuniform distribution in the brain is associated with different activity of homocarnosine-carnosine synthetase in the corresponding brain areas. At the preconvulsive stage of oxygen poisoning the homocarnosine content in all the brain areas does not change, the homocarnosine-carnosine synthetase activity is 32% lower. At the convulsive stage of hyperoxia the homocarnosine amount in the cerebral hemisphere decreases by 33%, in the midbrain and diencephalon -- by 70, in the medulla oblongata -- by 60, in the cerebellum -- by 58%. The decrease in the homocarnosine content correlates with that in the activity of homocarnosine-carnosine synthetase in the corresponding brain areas; in the cerebral hemispheres -- by 33%, in the midbrain and diencephalon -- by 50, in the medulla oblongata -- by 49, in the cerebellum -- by 40%.     

Developmental plasticity of central noradrenaline neurons after neonatal damage—changes in transmitter functions

The effects of neonatal 6-hydroxydopamine (6-OH-DA) treatment (systemic administration) on norasrenaline (NA) metabolism, trun over, and receptor charasteristics have been investigated in rat brain in the adult atage. This treatment is known to preferentially affect the locus coeruleus (LC) NA system leading to a marked NA denervation in the cerebral cortex and a hyperinnervation of NA nerve terminals in the pons and medulla oblongata without influencing the LC perikarya. The main NA metabolite, 3-methoxy-4-hydroxyphenylglycol (MOPEG) was reduced by about 70% in the cerebral cortex after 6-OH-DA-treatment at birth while the endogenous NA was almost completely depleted (-92%). The MOPEG levels were not significantly changed in the pons medulla after 6-OH-DA treatment in contrast to the 60% increase of the endogenous NA concentration. The relative reduction of NA in the cerebral cortex of 6-OH-Da treated rats increased in the cerebral cortex is increased after 6-OH-DA, while decreased in the pons-medulla, possibly related to changes in the activation of presynaptic α-adrenoreceptors in both regions. NA-induced formation of cAMP in vitro was found to be markedly increased in the cerebral cortex after 6-OH-DA, whereas no consistent change was observed in the pons medulla. Measurements of α- and β-receptor binding in vitro using radioligand techniques showed an increase of binding sites (20%–50%) for both receptors in the neocortex after 6-OH-DA, whereas no changes were observed in the pons medulla. The 6-OH-Da induced changes in NA turnover, cAMP generating systems, and receptor density may all represent compensatory processes following the altered development of the NA neurons induced by 6-OH-DA.     

Different degrees of lipid peroxidation in the CNS of young and adult rats exposed to short-term hypobaric hypoxia.

The authors studied the effect of short-term (20 min) hypobaric hypoxia at simulated altitudes of 7000 and 9000 m on the peroxidation of lipids in the cerebral cortex, subcortical formations, medulla oblongata and cerebellum of the laboratory rat. In 5- and 21-day-old rats, increased lipoperoxidation was recorded in all the studied regions of the brain. Differences were observed in sensitivity to the degree of hypoxia. In 5-day-old rats the response to both exposures was the same, but in 21-day-old animals exposure at 7000 m stimulated peroxidation in the cerebral cortex only (at 9000 m in all the parts of the CNS examined). In 35-day-old and adult rats, changes in the malondialdehyde concentration were likewise found after exposure at 9000 m, but not in every compartment (in 35-day-old rats in the cerebral cortex and subcortical formations and in adult rats in the cerebral cortex). In young rats, 30 and 60 min after exposure to hypoxia the malondialdehyde concentration was still higher than in older animals.     

Effects of ethanol on the concentration of neuropeptides, ACTH and corticosterone during immobilization stress

It was shown, that stress increased the level of ACTH, beta-endorphin and corticosterone in the blood plasma of the rat. Injection of ethanol (1 g/kg) decreased the level of ACTH, but increased the levels of beta-endorphin in the rat subjected to immobilization stress. The immobilization lowered the levels of met-enkephalin in the striatum and medulla oblongata, but increased the content of neuropeptide in the adrenal glands. The concentration of leu-enkephalin and DSIP remained unchanged following the stress. Ethanol reversed the action of immobilization on the level of met-enkephalin in the striatum, but increased the content of DSIP in the thalamus. These results indicate that ethanol modified the activity of pituitary-adrenal-axis during stress and probably the stress-protective action of ethanol partly performed with the involvement of DSIP.     

Fulminant Hepatic Failure in Rats Induces Oxidative Stress Differentially in Cerebral Cortex,Cerebellum and Pons Medulla

Hepatic Encephalopathy (HE) is one of the most common complications of acute liver diseases and is known to have profound influence on the brain. Most of the studies, available from the literature are pertaining to whole brain homogenates or mitochondria. Since brain is highly heterogeneous with functions localized in specific areas, the present study was aimed to assess the oxidative stress in different regions of brain-cerebral cortex, cerebellum and pons medulla during acute HE. Acute liver failure was induced in 3-month old adult male Wistar rats by intraperitoneal injection of thioacetamide (300 mg/kg body weight for two days), a well known hepatotoxin. Oxidative stress conditions were assessed by free radical production, lipid peroxidation, nitric oxide levels, GSH/GSSG ratio and antioxidant enzyme machinery in three distinct structures of rat brain-cerebral cortex, cerebellum and pons medulla. Results of the present study indicate a significant increase in malondialdehyde (MDA) levels, reactive oxygen species (ROS), total nitric oxide levels [(NO) estimated by measuring (nitrites + nitrates)] and a decrease in GSH/GSSG ratio in all the regions of brain. There was also a marked decrease in the activity of the antioxidant enzymes-glutathione peroxidase, glutathione reductase and catalase while the super oxide dismutase activity (SOD) increased. However, the present study also revealed that pons medulla and cerebral cortex were more susceptible to oxidative stress than cerebellum. The increased vulnerability to oxidative stress in pons medulla could be due to the increased NO levels and increased activity of SOD and decreased glutathione peroxidase and glutathione reductase activities. In summary, the present study revealed that oxidative stress prevails in different cerebral regions analyzed during thioacetamide-induced acute liver failure with more pronounced effects on pons medulla and cerebral cortex. Murthy Ch.R.K—Deceased while in service.     

Assay of 2-Hydroxyputrescine in Various Regions of Rat Brain by Gas Chromatography-Mass Spectrometry

2-Hydroxyputrescine in seven regions of single rat brains was measured with a sensitive, specific assay by gas chromatography-mass spectrometry. The regions were the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum, hippocampus, and midbrain. The level of 2-hydroxyputrescine was very high in the cerebral cortex and cerebellum, high in the medulla oblongata, hypothalamus, and hippocampus, and low in the striatum and midbrain. The level of 2-hydroxyputrescine in the cerebellum was significantly higher than in the striatum and midbrain.     

Repeated Idazoxan Increases Brain Imidazoline Receptors in Normotensive (WKY) but Not in Hypertensive (SHR) Rats

The specific binding of [3H]idazoxan in the presence of 10(-6) M (-)-adrenaline was used to evaluate the density of imidazoline receptors in the brain of spontaneously hypertensive (SHR) rats and sex- and age-matched normotensive Wistar-Kyoto (WKY) rats. In SHR rats the density of imidazoline receptors (cerebral cortex, hypothalamus, and medulla oblongata) was not different from that in normotensive (WKY) rats. However, repeated treatment with idazoxan consistently increased (23-80%) the density of imidazoline receptors in the various brain regions of WKY rats but not in SHR rats. In normotensive Sprague-Dawley rats, repeated treatment with the imidazoline drugs idazoxan and cirazoline also increased (33-37%) the density of imidazoline receptors in the cerebral cortex. The lack of regulation by idazoxan of the density of imidazoline receptors in the brain of SHR rats might reflect the existence of a relevant abnormality of these receptors in this genetic model of hypertension.