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.     

State of the opioid system in rats with different sensitivity to ethanol

In this work we investigated the content of opioids in plasma blood and the changes caused by ethanol (1.5 g/kg, i.p.) in midbrain opioid receptors of rats with different sensitivity to ethanol, as determined according to the duration of ethanol-induced sleep (DEIS). A receptor binding technique with selective delta-DADLE and mu-DAGO radioligands were used. Ethanol even at low dose produced changes in the midbrain opioid receptors which appeared after 6 hours. The response of the receptors and the content of opioids in plasma blood of rats with different DEIS were not identical.     

Effect of the hypothyroidism on the levels of different metabolites in pregnant rats

The effect of gestational hypothyroidism on some maternal and foetal metabolites were studied on pregnant rats after 24 h fasting. Thyroidectomy induced a decrease in body weight in the pregnant rats. Their foetuses showed lower weights than the controls. No difference was found in circulating glucose levels in the thyroidectomized pregnant rats, although an increase was found in their foetuses. Hepatic glycogen and total serum lipids decrease in hypothyroid pregnant rats. Cholesterol concentration increases as a result of hypothyroidism. However, foetuses coming from thyroidectomized mothers show an increase in their total lipid levels. Hypothyroidism in pregnant rats affects foetal development and metabolic changes are greatly manifested in the starved condition.     

Effect of a luliberine analogue (surfagon) on food conditioning in rats with different sensitivity to ethanol

Food conditioning worsened following a luliberine analogue surfagon administration in short-sleeping (SS) rats. Castration mostly inhibited the peptide effect. The findings suggest a possibility of the peptide effect occurring even without steroids.     

Neurotropic effects of luliberin analog in rats with different sensitivity to ethanol]

Luliberin's analogue (surfagon) has been established to activate shock-induced aggression of short-sleeping (SS) and long-sleeping (LS) rats in painful stress. The using of the castration and hypophysectomy has proved this effect to result from the direct neurotropic action of peptide. It has been shown, that SS rats differ from LS ones by more expressed reducing of painful aggressive and reference reactions after castration and hypophysectomy as well as by definitive peculiarities of peptidergic effects of surfagon.     

Effect of spontaneous ingestion of ethanol on brain dopamine metabolism

The effect of ethanol, either administered by gavage or voluntarily ingested, on brain dopamine (DA) metabolism was studied in alcohol-preferring and alcohol non-preferring rats. In alcohol non-preferring rats ethanol administration (2 g/kg) increased 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and reduced DA levels in the caudate nucleus and olfactory tubercle but was ineffective in the medial prefrontal cortex. In alcohol-preferring rats ethanol effect was greater than in non-preferring animals and ethanol influenced DA metabolism also in the medial prefrontal cortex. The effect of voluntary ethanol ingestion was studied in alcohol-preferring rats trained to consume their daily fluid intake within 2 hrs. Voluntary ingestion of ethanol (3.1 +/- 0.7 g/kg in 1 hr) increased DA metabolites and reduced DA levels in the caudate nucleus, olfactory tubercle and medial prefrontal cortex. The results suggest that voluntary ethanol ingestion increases the release of DA from nigro-striatal and meso-limbic DA neurons.     

Effect of ethanol on cyclic AMP levels in the rat brain

Ethanol decreased in a dose-dependent manner the cyclic AMP level in the rat brain and separation of the brain into several parts showed that this decrease was limited to the cerebellum. High doses of ethanol (4–6 g/kg) blocked the rise of cyclic AMP levels induced by decapitation in all brain areas studied. Pentobarbital treatment which produced central depression similar to that caused by a high dose of ethanol, also decreased the cyclic AMP level in the cerebellum but it prevented the postdecapitation rise only in the pons and medulla oblongata. Lower doses of ethanol (1–2 g/kg) enhanced the decapitation-induced rise of cyclic AMP levels in the pons and medulla oblongata.     

Effect of tryptophan on mediator content in the brain tissue of rats with different levels of seizure susceptibility

The effects of per orally administered tryptophan on serotonin and GABA levels in different brain areas were found to depend on initial levels of seizure susceptibility. Elimination of difference in the content of investigated mediator between animals with high and low seizure susceptibility was observed. Serotonin level was approximated to the initial one in rats with high seizure susceptibility but GABA level was approximated to the initial one in rats with low seizure susceptibility. Possible mechanismes of realization of tryptophan therapeutic effects are discussed.     

Effect of one-time and chronic administration of ethanol on the concentration of beta-endorphin in the brain of rats with different alcoholic motivation

The concentration of beta-endorphin was determined in the cortex of the large hemispheres, thalamus, striatum and medulla oblongata of rats with varying duration of ethanol anesthesia and after a single injection of ethanol (2.5 g/kg). The content of beta-endorphin was also measured in the brain of rats which preferred and rejected 15% ethanol during long-term (up to 10 months) alcoholization. The data obtained indicate that ethanol produces a specific effect on the endorphinergic system in different brain structures of animals predisposed to voluntary alcoholization. A possible involvement of the neuropeptide in the formation of alcohol tolerance and physical dependence is discussed.     

Effect of isolation stress on ethanol pharmacodynamics in the blood of rats

Head space chromatography was used to study the rate of ethanol excretion as criterion of the activity of the ethanol-oxidizing enzymatic system. Isolational stress was shown to be one of the factors determining induction of the ethanol-oxidizing erzymatic systems. The isolation-induced activity of these systems was reduced by diazepam administration. This fact may evidence the existence of central regulation of the activity of the enzymatic systems that metabolize ethanol.     

Regional alterations of dopamine and its metabolites in rat brain following portacaval anastomosis

Hyperammonemia and changes in brain monoamine metabolism have been proposed to contribute to the pathogenesis of the neuropsychiatric symptoms characteristic of human portal-systemic encephalopathy (PSE) resulting from chronic liver disease. Portacaval anastomosis (PCA) in the rat leads to sustained hyperammonemia and mild encephalopathy. In order to evaluate the role of dopamine (DA) metabolism in PSE, levels of DA and its metabolites were measured by HPLC with electrochemical detection in brain regions of rats with PCA at various stages of encephalopathy precipitated by ammonium acetate administration. Following ammonium acetate administration, rats with PCA rapidly develop severe neurological signs of encephalopathy progressing through loss of righting reflex to coma; sham-operated control animals administered ammonium acetate showed no such neurological deterioration. Concentrations of the DA metabolites DOPAC and HVA as well as [DA metabolites]/[DA] ratios, an indirect measure of DA turnover in brain, were increased in caudate-putamen, in cingulate and pyriform entorhinal cortices as well as in raphe nucleus and locus coeruleus. Increased DA metabolites, however, did not worsen at coma states of PSE. Increased DA turnover thus appears to relate to early neuropsychiatric and extrapyramidal symptoms of PSE.     

Effect of combined exposure to cadmium and ethanol on regional brain biogenic amine levels in the rat

The effect of ethanol ingestion on regional brain biogenic amine levels in cadmium exposed animals was examined. The rats were given either ethanol (1 g/kg, first week, 5 g/kg, second week and 10 g/kg for rest of the weeks) or cadmium (40 ppm in drinking water) or a combination of both for 8 weeks. Simultaneous exposure to cadmium and ethanol produced a greater elevation of norepinephrine in hypothalamus and mid brain when compared with rats receiving only cadmium. A significant elevation of 5-hydroxy-tryptamine in medulla oblongata was also noticed in cadmium and ethanol treated rats compared to cadmium alone treatment animals. The present results suggest industrial workers consuming alcohol may be more susceptible to cadmium neurotoxicity.     

Effect of direct and indirect dopamine agonists on brain extracellular ascorbate levels in the striatum and nucleus accumbens of awake rats

Systemic administration of direct and indirect dopamine agonists resulted in increased extracellular ascorbic acid levels in the striatum and, to a lesser degree, in the nucleus accumbens as measured by in vivo voltammetry. Intraperitoneal d-amphetamine sulfate (5mg/kg) increased ascorbate concentrations in striatal extracellular fluid. Amphetamine also increased extracellular ascorbate levels in the nucleus accumbens although more gradually and to a lesser extent. Intraperitoneal phenethylamine hydrochloride (20 mg/kg) following pargyline hydrochloride pretreatment (20 mg/kg) increased extracellular ascorbate levels in the striatum significantly above the small increase seen in the nucleus accumbens. The direct acting dopamine agonists Ly-141865 and Ly-163502 when given i.p. at 1 mg/kg, resulted in increased extracellular ascorbate concentrations in both brain areas, again with a significantly greater effect in the striatum. These results indicate that brain extracellular ascorbate levels can be modulated by dopaminergic neuro-transmission and that this modulation is quantitatively different in different dopamine-containing brain structures.     

Distribution and levels of dopamine and its metabolites in brains of reproductive workers in honeybees

To explore the role of dopamine and its metabolites for change of reproductive states of workers in honeybees (Apis mellifera), brain levels of dopamine relative substances were measured and localized in both normal workers and queenless workers. Dopamine and two possible metabolites of dopamine, N-acetyldopamine (NADA) and norepinephrine were detected in brain extracts. The brain levels of dopamine, NADA and norepinephrine were positively correlated with ovary development. Individuals with high dopamine levels had high levels of NADA or norepinephrine, suggesting that these metabolites might be involved in the change of reproductive sates of workers. Dopamine was distributed mainly in the protocerebrum, whereas NADA was in both the optic lobes and the protocerebrum. Dopamine levels in each distinct brain regions were higher in queenless workers than in normal workers, whereas there was a higher NADA level in the optic lobes in queenless workers than in normal workers. These results suggest that dopamine might be stored and/or released around the protocerebrum and the deutocerebrum, and also diffuse to the optic lobes where dopamine secretory cells are absent, resulting in high NADA levels in the optic lobes. The different manner of level changes of dopamine and its metabolites in each brain region might cause compound behavioural modulations in reproductive workers.     

Features of oxidative phosphorylation in brain mitochondria of rats with different sensitivity to oxygen insufficiency]

Oxidative phosphorylation parameters have been investigated in the isolated brain mitochondria of rats preliminary divided into non-resistant (NR) and high-resistant (HR) animals by their sensitivity to hypobaric hypoxia. During the NAD-dependent substrates oxidation it was shown that the identical effectiveness of the respiratory chain function in both groups of animals was reached at more tension of the oxidative processes. It has been established that at the identical effectiveness of the succinate oxidation by the brain mitochondria in both groups of animals compensatory potentialities of the succinate-oxidase pathway of oxidation is higher in the brain of the NR to hypoxia animals. It has been shown the regulated influence of the NAD-dependent pathway of oxidation activity on the succinate-oxidase site of respiratory chain. This influence is more expressed in the brain mitochondria of the NR animals that in the HR animals.     

Effect of 2-guanidinoethanol on levels of monoamines and their metabolites in the rat brain

The contents of monoamines and their metabolites in rat brains 3 hours after the intracerebroventricular injection of 6 mol of 2-guanidino-ethanol (GEt) were measured by HPLC. GEt which is a configurational analogue of 4-aminobutanoic acid (GABA) induced severe running fits and tonic-clonic convulsions as well as epileptic discharges. In GEt-administered rats, dopamine (DA) decreased in the cortex, hippocampus and hypothalamus. 3,4-Dihydroxyphenylacetic acid (DOPAC) increased to about the same level in all brain regions, therefore the distribution of DOPAC appeared to be homogeneous in the brain. The homovanillic acid levels also increased in the striatum and hippocampus. No significant change in the norepinephrine contents was observed in any region. The turnover ratio of DA increased significantly except in the striatum. Serotonin levels increased in the hypothalamus and midbrain by GEt administration, though 5-hydroxyindoleacetic acid levels showed no change in any of the brain regions. These data suggest that the activity of dopaminergic and serotonergic neurons are increased by GEt.