Regional distribution of tyrosine,tryptophan, and their metabolites in the brain of epileptic El mice

Tyrosine, tryptophan, and their metabolites in the brain of ddY, non-stimulated El (El (–)), and stimulated El (El (+)) mice were measured using the three dimensional HPLC. The tryptophan content was lower in El (+) than ddY and El (–) mice. The 5-hydroxytrytophan content was much higher in both El groups. The serotonin content of El (+) was higher than that of ddY and El (–) mice. The kynurenine content was remarkably high in the El mice. The dopamine content was lower in El (–) than in ddY mice, whereas it was greater in El (+) than in El (–) mice. The norepinephrine showed higher levels in El (+) mice. These facts suggest that El mice posess congenital metabolic abnormalities of tryptophan and tyrosine and that kynurenine may play an important role as convulsant in El mice seizures along with changes in serotonin, dopamine, and norepinephrine that are inhibitory agents and responded to the repetitive convulsions.     

Reduced and oxidized glutathione in brain and convulsions

Concentration changes of reduced glutathione (GSH) and oxidized glutathione (GSSG) were studied by fluorometric assay witho-phthalaldehyde to clarify the relationship between seizure mechanism and the glutathione redox state. In cerebellum the GSH/GSSG ratio was significantly decreased in the interictal stage of E1 mice (stimulated group), but in ddY mice this ratio was decreased before convulsions induced by pentylenetetrazol and during submaximal ECS. No change was found in the GSH/GSSG ratio of the cerebellum during and after convulsions induced by pentylenetetrazol and maximal ECS. GSH levels in cerebrum in the interictal stage of E1 mice (stimulated group) were lower compared to control E1 mice. In ddY mice submaximal ECS increased GSSG levels in cerebrum so that the GSH/GSSG ratio was decreased.     

Metabolic profile of opioid peptides differs in the hippocampus and striatum of seizure-susceptible E1 mice

We previously suggested that a deficit of anticonvulsant endogenous methionine enkephalin, in the cerebral cortex, septal area, hippocampus, and striatum of seizure-susceptible E1 mice plays a role in the pathogenesis of seizures. To determine whether a hypofunction of enkephalinergic neuron may be due to metabolic abnormalities of opioid peptides in the E1 mouse brain, we measured methionine enkephalin-like immunoreactivity (ME-LI) of 50 fractions eluted by high performance liquid chromatography obtained from those four regions of the brain of E1 and seizure-nonsusceptible ddY mice (the mother strain of E1 mice). We observed the same ME-LI patterns of 50 fractions in the cerebral cortex and septal area in E1 and ddY mice, whereas exhibited differing ME-LI patterns in the hippocampus and striatum in the two stains. Different ME-LI patterns may imply the difference in the metabolic profile of opioid peptides. Thus, an abnormal metabolism of opioid peptides in the hippocampus and striatum of the E1 mouse may be involved in the pathogenesis of seizures.     

Antidepressant-like behavioral and neurochemical effects of the citrus-associated chemical apigenin

Apigenin is one type of bioflavonoid widely found in citrus fruits, which possesses a variety of pharmacological actions on the central nervous system. A previous study showed that acute intraperitoneal administration of apigenin had antidepressant-like effects in the forced swimming test (FST) in ddY mice. To better understand its pharmacological activity, we investigated the behavioral effects of chronic oral apigenin treatment in the FST in male ICR mice and male Wistar rats exposed to chronic mild stress (CMS). The effects of apigenin on central monoaminergic neurotransmitter systems, the hypothalamic-pituitary-adrenal (HPA) axis and platelet adenylyl cyclase activity were simultaneously examined in the CMS rats. Apigenin reduced immobility time in the mouse FST and reversed CMS-induced decrease in sucrose intake of rats. Apigenin also attenuated CMS-induced alterations in serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), dopamine (DA) levels and 5-HIAA/5-HT ratio in distinct rat brain regions. Moreover, apigenin reversed CMS-induced elevation in serum corticosterone concentrations and reduction in platelet adenylyl cyclase activity in rats. These results suggest that the antidepressant-like actions of oral apigenin treatment could be related to a combination of multiple biochemical effects, and might help to elucidate its mechanisms of action that are involved in normalization of stress-induced changes in brain monoamine levels, the HPA axis, and the platelet adenylyl cyclase activity.     

Nisoxetine prevents the 6-hydroxydopamine induced decrease in post-decapitation convulsions

Intraventricular injection of 6-hydroxydopamine (60HDA) to rats caused a marked reduction in post-decapitation convulsions (PDC), which was also observed in rats given 60HDA systemically at birth. The reduction in PDC and norepinephrine (NE) content in brain and spinal cord was completely prevented by pretreatment with the selective norepinephrine uptake inhibitor, nisoxetine, but not by fluoxetine, a specific serotonin uptake inhibitor. Presumably nisoxetine prevented the reduction in PDC and NE levels by blocking the entry of 60HDA into the neuron via the membrane uptake pump, and thus preventing subsequent NE depletion and neuron degeneration. These data imply that NE neurons are involved in the neurological mechanism of PDC, although this does not exclude a role for other neurotransmitters such as serotonin (5HT) and dopamine (DA).     

Evaluation of the necessity for rapid inactivation of brain enzymes prior to analysis of norepinephrine dopamine and serotonin in the mouse.

Norepinephrine, dopamine and serotonin concentrations were measured in mouse whole brain. Animals were killed either by decapitation or by exposure to 250 msec microwave irradiation which produces irreversible inactivation of brain enzymes. The biogenic amines were determined by mass fragmentometry, fluorometry and by a combination of high performance liquid chromatography and an electrochemical detector. No differences were found in the levels of these neurochemicals between the two methods of animal sacrifice. Therefore, rapid inactivation of brain enzymes is not necessary prior to analysis for catecholamines and serotonin in mouse whole brain.     

Effects of piperine on convulsions and on brain serotonin and catecholamine levels in E1 mice

Convulsions of E1 mice were completely suppressed by 60 mg/kg of piperine injected intraperitoneally. The ED₅₀ was 21.1 mg/kg. The brain 5-HT, dopamine and norepinephrine levels were estimated 1 hour after the intraperitoneal injection of piperine. The 5-HT level was significantly higher in the cerebral cortex of piperine treated mice than in control mice. This increase may be related directly to the mechanism of inhibition of convulsions by piperine. On the other hand, lower levels of 5-HT were observed in the hippocampus, midbrain and cerebellum. The dopamine level in the piperine treated mice was markedly higher only in the hypothalamus, while the norepinephrine levels were lower in every part of the brain.     

Influence of dieldrin on serotonin turnover and 5-hydroxyindole acetic acid efflux in mouse brain

Chronic administration of dieldrin failed to produce any alteration of brain serotonin, norepinephrine or dopamine in mice, but caused an increase in 5-hydroxyindole acetic acid levels. The turnover rate of serotonin was unaffected by dieldrin. The probenecid induced accumulation rate of 5-hydroxyindole acetic acid was considerably lowered in dieldrin-treated mice. The results suggested a possible influence of dieldrin on 5-hydroxyindole acetic acid efflux from mouse brain.     

In vitro and in vivo binding of (E)- and (Z)-N-(iodoallyl)spiperone to dopamine D2 and serotonin 5-HT2 neuroreceptors

Apparent affinities (Ki) of (E)- and (Z)-N-(iodoallyl)spiperone [E)- and (Z)-NIASP) for dopamine D2 and serotonin 5-HT2 receptors were determined in competition binding assays. (Z)-NIASP (Ki 0.35 nM, D2; Ki 1.75 nM, 5-HT2) proved slightly more potent and selective for D2 sites in vitro than (E)-NIASP (Ki 0.72 nM, D2; Ki 1.14 nM, 5-HT2). In vivo, radioiodinated (E)- and (Z)-[125I]-NIASP showed regional distributions in mouse brain which are consonant with prolonged binding to dopamine D2 receptors accompanied by a minor serotonergic component of shorter duration. Stereoselective, dose-dependent blockade of (E)-[125I]-NIASP uptake was found for drugs binding to dopamine D2 sites, while drugs selective for serotonin 5-HT2, alpha 1-adrenergic and dopamine D1 receptors did not inhibit radioligand binding 2 hr postinjection. Specific binding in striatal tissue was essentially irreversible over the time course of the study, and (E)-[125I]-NIASP gave a striatal to cerebellar tissue radioactivity concentration of 16.9 to 1 at 6 hr postinjection. Thus, (E)-[125I]-NIASP binds with high selectivity and specificity to dopamine D2 sites in vivo.     

Alterations in the Function of Cerebral Dopaminergic and Serotonergic Systems Following Electroacupuncture and Moxibustion Applications: Possible Correlates with Their Antistress and Psychosomatic Actions

Alterations in cerebral monoamines following application of electroacupuncture were investigated using conscious rats with and without application of restraining stress. The dopamine and serotonin levels were significantly decreased in the nucleus accumbens, caudate putamen, and lateral hypothalamus and increased in the dorsal raphe nucleus by restraining stress. On the other hand, application of electroacupuncture on the lumbar and hindlimb segments eliminated the above changes in dopamine, while the changes in serotonin were attenuated by lumbar and hindlimb electroacupuncture. However, the effects of hindlimb electroacupuncture were greater than those of lumbar electroacupuncture. These results clearly indicate that lumbar and hindlimb electroacupuncture stimulations have differential effects on brain monoaminergic neurons in rats exposed to restraining stress. Moxa burning stimulation was applied to the lumbar and hindlimb segments of rats without restraining stress. The dopamine level was significantly increased in the midbrain substantia nigra-ventrotegmental area by hindlimb moxibusion. On the other hand, the serotonin levels were significantly increased in the nucleus amygdala by lumber moxibusion and decreased in the nucleus accumbens by hindlimb moxibusion. The present results indicate that electroacupuncture applied to the lumbar and hindlimb segments has an antistress effect, while the application of moxibustion to the lumbar and hindlimb segments was likely to stimulate the functions of mesocortical and mesolimbic dopaminergic and serotonergic neurons. We suggest that functional alterations in cerebral dopaminergic and serotonergic neurons are involved in the clinical efficacy of electroacupuncture and moxibustion, especially because of their antistress and psychosomatic actions.     

Dopamine and serotonin metabolism in striatum and in the septohippocampal pathway of the Snell dwarf mouse

Dopamine and serotonin neurotransmission has been investigated in striatum and in the septohippocampal pathway of the locomotor activity and memory deficient Snell dwarf mouse. In striatum a sharp decrease in 3-MT levels with a concomitant decrease in DA turnover is indicative of a strong decrement in the functional activity of striatal dopaminergic terminals in the mutant mouse. The observed enhancement in serotoninergic markers (5HT, 5HIAA, 5 HTP), at the opposite, provide evidence for an altered relationship between serotonin and dopamine striatal neurotransmission in the mutant mouse as compared to the normal mouse. Impairment in dopamine and serotonin neurotransmission has also been observed in the septohippocampal pathway where the removal of acidic metabolites of these neurotransmitters from brain appears to be disturbed. The data presented here are discussed with regard to previously noted alterations in cholinergic activity as well as to the behavioral disturbances of the dwarf mutant.     

Genetic vitamin E deficiency does not affect MPTP susceptibility in the mouse brain

Oxidative stress is involved in the degeneration of the nigrostriatal dopaminergic system in Parkinson's disease (PD). Vitamin E (alpha-tocopherol) is a potent antioxidant in the cell membrane that can trap free radicals and prohibit lipid peroxidation. The retention and secretion of vitamin E are regulated by alpha-tocopherol transfer protein (TTP) in the brain and liver. Dysfunction of TTP results in systemic deficiency of vitamin E in humans and mice, and increased oxidative stress in mouse brain. In this study, we investigated the effect of vitamin E deficiency in PD development by generating an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD using TTP knockout (TTP-/-) mice. Vitamin E concentration in the brains of TTP+/- mice was half that in TTP+/+ mice, and in TTP-/- mice, was undetectable. MPTP treatment tended to decrease striatal dopamine, but the effect was comparable and not significant in any of the three genotypes. Furthermore, the extent of loss of dopaminergic cell bodies in the substantia nigra did not differ among the groups. One the other hand, oral administration of vitamin E resulted in the partial protection of striatal dopaminergic terminals against MPTP toxicity. Our results suggest that vitamin E does not play a major protective role in MPTP-induced nigrostriatal dopaminergic neurodegeneration in the brain.     

Low selenium diet increases the dopamine turnover in prefrontal cortex of the rat

It has been proposed that interaction of catecholamines and indoleamines with free radicals may result in the formation of endogenous neurotoxins. In order to better understand the mechanisms involved in neurodegenerative disorders showing evidence of oxidative stress, we have studied the basal concentrations and the turnover rates of dopamine, noradrenaline, serotonin and their metabolites in the prefrontal cortex of rats that were fed on control or low selenium diets. Nutritional deficit of selenium decreases the brain antioxidant protection in experimental conditions by the decrease in glutathione peroxidase activity.

The dopamine and serotonin turnover increased and noradrenaline and 5-hydroxy-3-indoleacetic acid turnover decreased compared to experimental control animals. The increase of dopamine turnover in experimental rats was accompanied by an increase in tyrosine hydroxylase activity. These results suggest that the decrease of brain protection against oxidative damage could induce brain damage by disturbing the turnover rate of some monoamines.     

Developmental and regional alteration of methionine enkephalin-like immunoreactivity in seizure-susceptible E1 mouse brain

Methionine enkephalin-like immunoreactivity (ME-LI) in the brain of El mice (seizure-susceptible strain) was measured by radioimmunoassay (RIA) to elucidate the relation between seizures and the opioid system. The lyophilized supernatants of tissue extracts were subjected to ME RIA. The concentration of ME-LI in 25-day-old El mice that had no seizures was significantly decreased in the hippocampus. At the age of 50 days when El mice displayed abortive seizures, the levels of ME-LI in both El(+) and nonstimulated El(o) mice were also significantly reduced in the hippocampus and septal area. It was further shown that the ME-LI concentrations in both 150-day-old adult El(+) during interictal periods and El(o) mice were markedly decreased in the cerebral cortex, septal area, and striatum, as compared with the corresponding regions in ddY mice (seizurenonsusceptible strain; the mother strain of El). The decrease of ME-LI in the El mouse brain was generally compatible with our previous findings concerning the up-regulation of opioid delta receptors in this species. These results suggest that the reduction of ME-LI in the El mouse brain is not due to convulsions, but could be associated with the pathogenesis of seizure diathesis and seizure manifestations in the El mouse.     

Involvement of the somatostatin-2 receptor in the anti-convulsant effect of angiotensin IV against pilocarpine-induced limbic seizures in rats

The anti-convulsant properties of angiotensin IV (Ang IV), an inhibitor of insulin-regulated aminopeptidase (IRAP) and somatostatin-14, a substrate of IRAP, were evaluated in the acute pilocarpine rat seizure model. Simultaneously, the neurochemical changes in the hippocampus were monitored using in vivo microdialysis. Intracerebroventricularly (i.c.v.) administered Ang IV or somatostatin-14 caused a significant increase in the hippocampal extracellular dopamine and serotonin levels and protected rats against pilocarpine-induced seizures. These effects of Ang IV were both blocked by concomitant i.c.v. administration of the somatostatin receptor-2 antagonist cyanamid 154806. These results reveal a possible role for dopamine and serotonin in the anti-convulsant effect of Ang IV and somatostatin-14. Our study suggests that the ability of Ang IV to inhibit pilocarpine-induced convulsions is dependent on somatostatin receptor-2 activation, and is possibly mediated via the inhibition of IRAP resulting in an elevated concentration of somatostatin-14 in the brain.     

THE EFFECT OF AMINO-OXYACETIC ACID ON BRAIN CATECHOLAMINES

Abstract— —Administration of amino-oxyacetic acid (AOAA) to rats induced a pronounced decrease of midbrain norepinephrine (NE) and adrenal epinephrine (E) after 30 min, at which time the GABA level of midbrain had increased to 117 per cent of the initial value. The concentrations of NE in the pons-medulla and of dopamine (DA) in the cerebral hemispheres were not changed.
Further increases in brain GABA were accompanied by a rise of NE in midbrain and pons-medulla beginning 1 hr after AOAA administration. A rise of cerebral DA level was observed only after 4 hr. Six hours after AOAA administration the levels of both NE and DA in brain were reduced.
From the results of these and other studies, where administration of small amounts of GABA were shown to affect brain NE and serotonin levels, it is suggested that monoamines may be involved in the physiological action of GABA in the brain.     

Different roles of dopamine and serotonin in conditioned passive avoidance response of rats

Deamination of dopamine and serotonin by monoamine oxidase was studied in the prefrontal cortex, striatum, hippocampus and amygdaloid complex of the brain of rats during retrieval of conditioned passive avoidance response. Changes in the dopamine and serotonin metabolism were observed in different brain structures. A decrease in dopamine-deaminating activity of monoamine oxidase was found in the hippocampus, striatum and prefrontal cortex. At the same time, serotonin-deaminating activity of the enzyme was decreased in the striatum and increased in the amygdaloid complex, whereas it did not change in the prefrontal cortex and hippocampus. The observed changes in dopamine metabolism in the prefrontal cortex and hippocampus and serotonin metabolism in the amygdaloid complex indicate that dopamine and serotonin are involved in the regulation of two different processes mediating the memory trace retrieval. Dopamine is involved in neuronal mechanisms of information processes providing the strategy of behavior, whereas serotonin is related to emotional mechanisms of memory.     

Alteration in the content of biogenic amines in two stocks of Drosophila virilis and their hybrids in ontogenesis and under heat stress

The levels of dopamine and serotonin in two stocks of D. virilis and their F1 hybrids throughout ontogenesis and under heat stress (for 60 min at 32 degrees C) were examined. Sharp increase in dopamine levels was reported under pupariation and with emergence of adults; alterations in serotonin levels were not so obvious. The concentration of dopamine in adults was shown to be considerably higher (more than twice) in the stock 147 than that in the stock 101. Significant increase of dopamine quantity in both stocks was observed under heat stress (serotonin remaining unchanged), while the level of response in the stock 101 was twice as high as in adults of the stock 147. The response typical of the stock 147 was prevailing in the hybrids F1 (147 x 101).     

Genotype-treatment interaction between amantadine and chlorpromazine in the mouse.

1. Repeated administration of amantadine prior to chlorpromazine to two different strains of mice altered both locomotor activity, concentrations of brain biogenic amines and selected major metabolites as a function of mouse strain. 2. Amantadine antagonized chlorpromazine effect on motility which was associated with increases in whole brain levels of homovanillic acid in the CDF-1 but not C57BL/6 mice. 3. Conversely, the treatment with amantadine prior to chlorpromazine reduced whole brain normetanephrine and 5-hydroxyindoleacetic acid levels from respective controls in the C57BL/6 and CDF-1 mice, respectively. 4. The results suggest that genetic factors underly differential alteration of brain dopamine and serotonin which may underly the mechanism of amantadine efficacy in neuroleptic-induced extrapyramidal disorders and to the variable responses to amantadine therapy.     

Age- and seizure-related changes in noradrenaline and dopamine in several brain regions of epileptic El mice

Noradrenaline (NA) and dopamine (DA) levels in six brain regions of stimulated and nonstimulated El (El[s] and El[ns]) mice and their maternal ddY mice were determined at various ages and various times after a convulsion. The NA levels in the striatum and hippocampus of 12-week-old El[s] and El[ns] mice were lower than in ddY mice, and remained lower in 23-week-old El[s] mice, but not in El[ns] mice. DA levels were lower in the striatum of El[s] mice than in El[ns] and ddY mice at 16 and 23 weeks of age. NA levels decreased during seizure in the striatum and hippocampus of El[s] mice, and returned to preconvulsive levels 1 hr after convulsion in the striatum and 30 min in the hippocampus. DA levels in the striatum of El[s] mice decreased during convulsion and increased from 1 to 10 min after convulsion. These changes suggest that the NAergic systems in the striatum and hippocampus and the DAergic system in the striatum have important roles in relation to seizure susceptibility in El mice.