Chronic Stress Increases Serotonin and Noradrenaline in Rat Brain and Sensitizes Their Responses to a Further Acute Stress

The effects of 1 h/day restraint in plastic tubes for 24 days on the levels of serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), tryptophan (TP), and noradrenaline (NA) in six regions of rat brain 20 h after the last restraint period were investigated. The levels of 5-HT, 5-HIAA, and NA but not TP increased in several regions. The effects of 1 h of immobilization on both control and chronically restrained rats were also studied. Immobilization per se did not alter brain 5-HT, 5-HIAA, and TP levels, but decreased NA in the pons plus medulla oblongata and hypothalamus. However, immobilization after chronic restraint decreased 5-HT, increased 5-HIAA, and decreased NA in most brain regions in comparison with values for the chronically restrained rats. We suggest that chronic restraint leads to compensatory increases of brain 5-HT and NA synthesis and sensitizes both monoaminergic systems to an additional acute stress. These changes may affect coping with stress demands.     

Inhibitory effects of cis- and trans-resveratrol on noradrenaline and 5-hydroxytryptamine uptake and on monoamine oxidase activity

This study investigated for the first time the potential effects of cis- and trans-resveratrol (c-RESV and t-RESV) on noradrenaline (NA) and 5-hydroxytryptamine (5-HT) uptake by synaptosomes from rat brain, on 5-HT uptake by human platelets, and on monoamine oxidase (MAO) isoform activity. Both c-RESV and t-RESV (5-200 microM) concentration-dependently inhibited the uptake of [3H]NA and [3H]5-HT by synaptosomes from rat brain and the uptake of [3H]5-HT by human platelets. In both experimental models, t-RESV was slightly more efficient than c-RESV. Furthermore, in synaptosomes from rat brain, the RESV isomers were less selective against [3H]5-HT uptake than the reference drug fluoxetine (0.1-30 microM). On the other hand, both c-RESV and t-RESV (5-200 microM) concentration-dependently inhibited the enzymatic activity of commercial (human recombinant) MAO isoform (MAO-A and MAO-B) activity, c-RESV being slightly less effective than t-RESV. In addition, both RESV isomers were slight but significantly more selective against MAO-A than against MAO-B. Since the principal groups of drugs used in the treatment of depressive disorders are NA/5-HT uptake or MAO inhibitors, under the assumption that the RESV isomers exhibit a similar behaviour in humans in vivo, our results suggest that these natural polyphenols may be of value as structural templates for the design and development of new antidepressant drugs with two important biochemical activities combined in the same chemical structure: NA/5-HT uptake and MAO inhibitory activity.     

家兔若干与下行抑制有关的中枢部位中去甲肾上腺素、5-羟色胺和脑啡肽在针刺镇痛中的变化

应用推挽灌流技术、去甲肾上腺素(NA)放射酶学法和亮-脑啡肽放射免疫法观察不同脑区 NA 和脊髓背角亮-脑啡肽的释放。应用分子筛柱层析分离家兔不同脑区的5-羟色胺(5-HT)和5-羟吲哚乙酸(5-HIAA),并对它们进行荧光微量测定。以此来阐明针刺镇痛时 NA、5-HT 和亮-脑啡肽在下行抑制中的作用。1.家兔电针20 min,痛阈显著提高,此时中脑导水管周围灰质(PAG)和中缝大核(NRM)的 NA 释放显著减少,而 Al 核团和脊髓背角的 NA释放显著增加。2.电针镇痛时,PAG、延脑中缝核区和脊髓的5-HT 和5-HIAA 含量均有显著增加,除 PAG 外,这种增加的出现较 NA 为晚。提示可能在针刺镇痛的下行抑制中,NA 的参予较5-HT 为早。3.针刺镇痛时脊髓背角亮-脑啡肽的释放也明显增加。     

Role of monoamine oxidase-B in medroxyprogesterone acetate (17-acetoxy-6 alpha-methyl-4-pregnene-3, 20-dione) induced changes in brain dopamine levels of rats

The effect of medroxyprogesterone acetate (MPA) on brain monoamine levels and monoamine oxidase (MAO) activity was studied in adult, healthy, non-pregnant female rats. MpA was injected in a single dose of 100 mg/kg i.m. Dopamine (DA), noradrenaline (NA), 5-hydroxytryptamine (5-HT) levels and MAO activity were estimated fluorometrically in rat brian. No change in DA, NA, 5-HT or MAO activity was observed after 7 days of MPA treatment while a significant decrease in DA levels along with a significant increase in MAO activity was observed after 21 days of MPA treatment. However, there was no change in NA and 5-HT levels after 21 days of MPA administration. The selective reduction of DA by MPA could be due to an increase in MAO-B activity. MPA does not appear to increase MAO-A activity because neither of the specific substrates (NA and 5-HT) of MAO-A was found to be decreased inspite of the increase in MAO activity as estimated by the kynuramine method. These findings suggest the importance of MAO-B also in DA metabolism in rat brain.     

THE EFFECTS OF OUABAIN AND THE ACTIVATION OF NEURAL MEMBRANE ATPase BY BIOGENIC AMINES

Abstract— The effects of 10⁻⁵ m -noradrenaline (NA), 5-hydroxytryptamine (5-HT) and dopamine (DA) on the activities of Na⁺-K⁺ ATPase (EC 3.6.1.3) were studied in synaptic membranes from 6 regions of the rabbit brain. NA and 5-HT stimulated the synaptic membrane Na⁺-K⁺ ATPase from the cerebrum, but none of the amines influenced the activity of this enzyme in the other brain regions. The Na⁺-K⁺ ATPase activity of the cerebral synaptic membrane isolated at the 0.8/0.9 m & 0.9/1.0 m interphase of a sucrose density gradient was increased two-fold by 10⁻⁵ m -NA and 5-HT. The Na⁺-K ⁺ ATPase recovered at the 1.0/1.2 m interphase was not influenced by NA, DA or 5-HT. NA, DA and 5-HT did not activate the Mg ATPase of synaptic membranes from any of the 6 brain regions or whole brain synaptic vesicles. The cortex synaptic membrane (Na⁺-K⁺) ATPase is postulated to have a direct role in the uptake of the biogenic amines. An indirect role is proposed for this enzyme in amine uptake into brain stem.     

Influence of hypo- and hyperthyroidism on the turnover rate of noradrenaline, dopamine and serotonin in various rat cerebral structures]

The effect of chronic treatment with tyroxine (T4) or propylthiouracile (PTU) on the turnover of norepinephrine (NE), dopamine (DA) and 5-hydroxytryptamine (5-HT) has been studied in various areas of the rat brain (brain stem, hypothalamus, striatum and "rest of the brain"). The turnover of NE and DA was determined by the decay in endogenous levels after inhibition of tyrosine hydroxylase by alpha-methylparatyrosine and the turnover of 5-HT was evaluated by the initial accumulation of endogenous 5-HT after inhibition of monoamine oxydase by pargyline. T4 treatment accelerated the release of DA from the striatum but had no significant effects on NA release in the various cerebral areas : nevertheless the NE endogenous level was significantly reduced in the brain stem. PTU treatment delayed the release of DA and NA only from the "rest of the brain". Concerning 5-HT, the only significant variation was observed in the hypothalamus of PTU-treated rats and implied increased turnover. The possible relations between the changes in cerebral monoamines turnover and the behavioural alterations which are observed in thyroid disfunction are discussed.     

Microdialysis Study of Modification of Hypothalamic Neurotransmitters in Streptozotocin-Diabetic Rats

Abstract: Neurochemical changes in the ventromedial hypothalamus (VMH) after a single intravenous injection of streptozotocin were examined, using in vivo brain microdialysis under free-moving conditions. Although streptozotocin-induced diabetes produced significant decreases in extracellular concentrations of noradrenaline (NA), serotonin (5-HT), and their metabolites in the VMH, the ratios of 3-methoxy-4-hydroxyphenylglycol/NA and 5-hydroxyindoleacetic acid (5-HIAA)/5-HT were increased. Experimental diabetes led to a pronounced increase in extracellular GABA, which correlated strongly with the decrease in dialysate levels of NA, and to a smaller extent with that of 5-HT. A modification of dopamine (DA) metabolism was induced in the VMH of diabetic rats, whereas there was no change in dialysate DA levels. Daily injections of insulin were able to restore their levels to normal in the areas tested in the microdialysis study. The equal increases in dialysate 5-HT and 5-HIAA and the better restoration of the 5-HIAA/5-HT ratio after insulin therapy indicate that serotonergic activity may depend on the levels of circulating insulin more than on noradrenergic activity. Circulating NA was reduced in streptozotocin-diabetic rats, suggesting that the diabetes-induced reduction in sympathetic activity is accompanied by decreases in NA, or 5-HT, or both, in the VMH.     

Serotonin, dopamine, noradrenaline and their metabolites: levels in the brain of the house cricket (Acheta domesticus L.) during a 24-hour period and after administration of quipazine--a 5-HT2 receptor agonist.

1. The levels of 5-HT, DA, NA and DA metabolites (NADA, DOPAC) measured by HPLC (with electrochemical detection) in the brain of the house cricket did not change over a 24-hr period. The level of 5-HIAA, a 5-HT metabolite, was below the limit of detection. 2. The 5-HT and DOPAC levels decreased and NADA increased after quipazine injection but DA and NA levels did not change after it. 3. [3H]Ketanserin was used to identify serotonin receptors bound to sites in the house cricket brain with a KD of 5 nM and a concentration of Bmax 180 fmol/mg protein.     

Effect of clorgyline and of alpha-methyl-p-tyrosine on the plasma levels of corticosterone in the rat

The effect of a type A MAO inhibitor, clorgyline, injected alone or with alpha-methyl-p-tyrosine (aMpT) on the plasmatic corticosterone levels estimated at 9 a.m. and 5 p.m. has been studied in male Wistar rats. The clorgyline injected alone produced significant decreases in corticosterone values, especially at 5 p.m., determining a variation lack between the morning and the afternoon levels. When alpha-MpT is associated to IMAO, increases at both points of the day considered in this experiment take place. The amount of NA and 5-HT in the brain was also estimated; clorgyline high increases in Na and 5-HT contents, 5-HT; aMpT reduces the effect of clorgyline, especially as regards content. The results are discussed in relation to this highly specific MAO inhibitor and with the role of these amines as modulators of ACTH secretion. In view of the changes introduced by the aMpT injection, the modifications produced by clorgyline alone are related to NA, but to 5-HT, when the NA synthesis has been interrupted by the tyrosine hydroxylase inhibitor.     

Inhibition of tryptophan hydroxylase: Neurochemical action of a catecholamide seizure-inducing agent

H13/04, an audiogenic seizure-inducing catecholamide, has previously been demonstrated to decrease the accumulation of 5-hydroxytryptophan (5-HTP), while increasing the accumulation of dihydroxyphenylalanine (DOPA) after aromatic acid decarboxylase inhibition in vivo. The present study examined the effect of H13/04 on intracellular storage, release, and metabolism of serotonin (5-HT) and noradrenaline (NA) in vitro in order to differentiate between the primary effects of the drug and possible secondary effects due to neurotransmitter interaction. H13/04 had no effect on NA synthesis by brain minces from C57BL/6 mice, but did have a marked effect on [³H]5HT synthesis from [³H]tryptophan in mouse brain minces. H13/04 was subsequently shown to competitively inhibit tryptophan hydroxylase. The data presented in this study indicate that the primary action of H13/04 on biogenic amines is to decrease the synthesis rate of 5-HT by competitive inhibition of tryptophan hydroxylase. The lack of any effect on NA in vitro is consistent with the hypothesis that the primary biochemical action of the drug is on the 5-HT system and that the action on NA in vivo is an indirect effect possibly secondary to the inhibition of 5-HT synthesis.     

Changes in rat brain monoamine turnover following chronic antidepressant administration

Changes in rat brain monoamine turnover were studied following the chronic administration of five agents which markedly differ in their patterns of monoamine uptake inhibition. Compounds (10 mg/kg, i.p.) were injected once daily for 14 days and experiments undertaken 24 h after the last injection. Chronic administration of desipramine or mianserin elevated brain MOPEG-SO₄ content and the α-MT-induced reduction in brain NA levels was enhanced by chronic desipramine. either antidepressant altered turnover of brain DA or 5-HT. Steady state levels of brain 5-HIAA or striatal levels of DOPAC or HVA were also unchanged. Chronically administered Org 6582, a selective inhibitor of 5-HT uptake, decreased basal and attenuated the probenecid-induced increase iin brain 5-HIAA levels. Chronic Org 6582 had no effect on NA or DA turnover and on the levels of MOPEG-SO₄, DOPAC or HVA. Neither maprotiline nor chlorimipramine altered turnover of NA, DA or 5-HT or levels of metabolites. Thus, in contrast to the acute situation, chronically administered desipramine increases rat brain NA turnover. Conversely, acute and chronic Org 6582 administration yield similar findings, viz. a decrease in turnover. These observations suggest that rat brain 5-HT systems are more resistant than NA systems to adaptive changes following a prolonged inhibition of monoamine uptake.     

A modified screening method for rapid simultaneous determination of dopamine, noradrenaline and serotonin in the same brain region

A modification of previously published fluorimetric methods for brain noradrenaline (NA), dopamine (DA), and serotonin (5-HT) assay is presented in this paper. The modification improved the sensitivity to 5-HT and resulted in a less time-consuming and less expensive method for noradrenaline and dopamine determination. The assay can be used for simultaneous estimation of NA, DA and 5-HT as well as for turnover studies, utilizing catecholamine synthesis inhibition or monoaminoxidase inhibition.     

Selective reduction by isolation rearing of 5-HT1A receptor-mediated dopamine release in vivo in the frontal cortex of mice

Serotonin (5-HT)1A receptors modulate in vivo release of brain monoaminergic neurotransmitters which may be involved in isolation-induced aggressive behavior. The present study examined the effect of isolation rearing on the 5-HT1A receptor-mediated modulation of dopamine (DA), 5-HT and noradrenaline (NA) release in the frontal cortex of mice. The selective 5-HT1A receptor agonist (S)-5-[-[(1,4-benzodioxan-2-ylmethyl)amino]propoxy]-1,3-benzodioxole HCl (MKC-242) increased the release of DA and NA and decreased the release of 5-HT in the frontal cortex of mice. The effect of MKC-242 on DA release was significantly less in isolation-reared mice than in group-reared mice, while effects of the drug on NA and 5-HT release did not differ between both groups. The effect of the other 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin on cortical DA release was also less in isolation-reared mice than in group-reared mice, and that of the drug on cortical 5-HT release did not differ between both groups. In contrast to MKC-242-induced DA release, amphetamine-induced increase in cortical DA release in vivo was greater in isolation-reared mice. The present findings suggest that isolation rearing enhances the activity of cortical dopaminergic neurons and reduces selectively the 5-HT1A receptor-mediated release of DA in the cortex.     

Significance of the reciprocal relationship of monoaminergic systems of the brain in the pharmacological compensation of 6-hydroxydopamine-induced behavior disorders in animals

The paper studied the methods of compensation of the abnormal emotional behaviour by means of pharmacological substances, which change the content of biogenic amines. The experiments made in the Wistar rats (n-54) whose frustration reaction was diminished by neonatal treatment of 6-OHDA. It was established that recovery of the disturbances in the frustration reaction in the animals with chronic brain system activity deprivation can be achieved not only by the activation of NA system (L-DOPA, DOPS) but also by deactivation of the 5-HT brain system activity (PCPA). These findings confirm suggestion about existence of reciprocal relationship between NA and 5-HT brain systems.     

Simultaneous determination of catecholamines in rat brain tissue by high-performance liquid chromatography

A novel and highly sensitive method has been developed for the determination of catecholamines [noradrenaline (NA), dopamine (DA), serotonin (5-HT) and their metabolites 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA)] in brain tissue. The method uses isocratic reversed-phase HPLC with amperometric end-point detection. The calibration curve was linear over the range 10–150 pg on-column. The assay limits of detection for NA, DA, 5-HT, 5-HIAA and HVA were 3.8, 3.8, 6.8, 5 and 7.5 pg on-column, respectively. The mean inter- and intra-assay relative standard deviations (RSDs) over the range of the standard curve were less than 5%. The absolute recoveries averaged 99.1%, 99.5%, 97.7%, 99.5% and 98.8% for NA, DA, 5-HT, 5-HIAA and HVA, respectively.     

Stress by forced swimming in the rat: effects of mianserin and moclobemide on GABAergic-monoaminergic systems in the brain

The stress caused by forced swimming in male rats provoked a decrease in brain NA levels without changes in DA and 5-HT content, MAO and GABAergic activity. Acute or chronic treatment with mianserin did not modify the decrease in NA concentration in the brain of stressed rats. Acute treatment with moclobemide (IMAO) did not modify the decrease in NA content caused by stress; chronic treatment blocked the decrease in NA content in stressed rats.     

Two-way avoidance and acute shock stress induced alterations of regional noradrenergic, dopaminergic and serotonergic activity in Roman high- and low-avoidance rats

Various brain regions of male RHA/Verh and RLA/Verh rats were dissected out and deep-frozen immediately after 30 min in a shuttle box involving a) no shock (control), b) 40 inescapable shocks or c) 40 avoidable shocks. The RHA/Verh rats used in the "c" category exhibited about 80-85% learned avoidance. 5-HT, 5-HIAA, NA, MHPG-SO4, DA, DOPAC and HVA levels were subsequently measured in selected regions. NA levels were considerably reduced in the hypothalamus and pons/medulla of both selected lines of rats after acute shock stress, supporting the results of numerous studies which have indicated that NA turnover is nonspecifically increased by all types of stress, at least in those regions. An increase in cortical MHPG-SO4 and a reduction in hypothalamic 5-HT seen after avoidance learning also occurred after shock stress in RHA/Verh rats. Whereas RLA/Verh rats showed an increased metabolism of 5-HT in the hypothalamus and pons/medulla after shock stress, RHA/Verh rats showed the opposite response in the hypothalamus after the same treatment. A reduction in 5-HT metabolism was also evident in RHA/Verh rats, after avoidance learning, in the cortex, hippocampus and hypothalamus. These results indicated, pending further studies regarding, for example, possible genetic differences in tryptophan uptake and utilization, that 5-HT probably plays at least a modulatory role in the reaction to stress, and in avoidance behavior. That role may be either active or passive, depending upon the emotional status of the subjects. In regard to the DA responses measured in striatum and hypothalamus of the two rat lines, some divergent inter-treatment tendencies, as well as some similarities, were seen in DA metabolism in both regions, but almost none of the differences were significant.     

Effects of desipramine on regional serotonin synthesis in the rat brain: acute and chronic autoradiographic studies

Various studies have implicated the involvement of noradrenaline (NA) and/or serotonin (5-hydroxytryptamine (5-HT)) in the pathogenesis and treatment of depression. The aim of the present study was to investigate the effects of acute and 7 days of administration of desipramine, a NA re-uptake inhibitor, on the rate of 5-HT synthesis in the rat brain. The study was done by an autoradiographic method using alpha-[14C]-methyl-L-tryptophan as a tracer. The acute (10mg/kg, i.p., 2h before i.v. infusion of the tracer) or 7 days of desipramine (10mg/kg per day, i.p.) did not affect plasma tryptophan (Trp) concentrations, as compared to control (saline treated) rats. Acute treatment with desipramine decreased the rate of 5-HT synthesis in the brain regions that contain 5-HT cell bodies between 19 and 28%, and increased the rate of 5-HT synthesis in the majority of areas containing 5-HT terminals between 21 and 65%. In contrast to the acute treatment, a 7-day administration increased 5-HT synthesis rates in the dorsal raphe (24%), but decreased it in raphe magnus (35%), superior olive (45%), caudate (31%), superior (38%) and inferior (53%) colliculus, and in the auditory cortex (35%). This suggests that the effect of desipramine on 5-HT synthesis rate is time-dependent and differs in the cell bodies and structures containing 5-HT nerve terminals.     

Serotonin,dopamine, noradrenaline and their metabolites: Levels in the brain of the house cricket (Acheta domesticus L.) during a 24-hour period and after administration of quipazine—a 5-HT2 receptor agonist

1. The levels of 5-HT, DA, NA and DA metabolites (NADA, DOPAC) measured by HPLC (with electrochemical detection) in the brain of the house cricket did not change over a 24-hr period. The level of 5-HIAA, a 5-HT metabolite, was below the limit of detection.2. The 5-HT and DOPAC levels decreased and NADA increased after quipazine injection but DA and NA levels did not change after it.3. [³H]Ketanserin was used to identify serotonin receptors bound to sites in the house cricket brain with a K_d of 5 nM and a concentration of B_max 180 fmol/mg protein.     

Neurotransmitter Changes in Guinea-Pig Brain Regions Following Soman Intoxication

The effects of the organophosphate acetylcholinesterase (AChE) inhibitor soman (31.2 micrograms/kg s.c.) on guinea-pig brain AChE, transmitter, and metabolite levels were investigated. Concentrations of acetylcholine (ACh) and choline (Ch), noradrenaline (NA), dopamine (DA), 5-hydroxytryptamine (5-HT), and their metabolites, and six putative amino acid transmitters were determined concurrently in six brain regions. The brain AChE activity was maximally inhibited by 90%. The ACh content was elevated in most brain areas by 15 min, remaining at this level throughout the study. This increase reached statistical significance in the cortex, hippocampus, and striatum. The Ch level was significantly elevated in most areas by 60-120 min. In all regions, levels of NA were reduced, and levels of DA were maintained, but those of its metabolites increased. 5-HT levels were unchanged, but those of its metabolites showed a small increase. Changes in levels of amino acids were restricted to those areas where ACh levels were significantly raised: Aspartate levels fell, whereas gamma-aminobutyric acid levels rose. These findings are consistent with an initial increase in ACh content, resulting in secondary changes in DA and 5-HT turnover and release of NA and excitatory and inhibitory amino acid transmitters. This study can be used as a basis to investigate the effect of toxic agents and their treatments on the different transmitter systems.