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.     

Plasma free and sulphated catecholamines after ultra-long exercise and recovery

We investigated the early and late effects of two types of ultra-long exercise on sympatho-adrenal and dopaminergic activity. With this aim both free and sulphoconjugated plasma catecholamines (CA), noradrenaline (NA), adrenaline (A), and dopamine (DA) were determined in two groups of athletes immediately after completion of 24-h running or a 10-h triathlon and on recovery during the next 1-3 days. Both races stimulated the sympathetic activity, but differences were observed in the CA pattern: the 24-h run induced a marked elevation of free and sulphoconjugated NA (+175% and +180%, respectively) but failed to alter significantly A and DA levels. The triathlon challenge increased the three conjugated CA (NA sulphate +350%; A sulphate +110%; DA sulphate +270%) and to a lesser extent free CA (NA +45%; A +30%). On the first post-exercise morning, a sustained intense noradrenergic activity was still present in the 24 h-runners, as evidenced by the large increase in free and sulphated NA levels (+140% and +100%, respectively). Such a prolonged activity was also indicated after completion of the triathlon, by the increase of NA sulphate (+140%) observed on the 1st recovery day. However, after the triathlon there was a decreased release of A from the adrenal medulla for several days. These data show that both types of ultralong exercise are able to induce for several hours a sustained sympathetic activation during the test and in the recovery period. Furthermore, the study shows that plasma conjugated CA may provide delayed and cumulative indexes of sympathetic activation, complementary to the instantaneous markers such as free CA.     

Seasonal and Daily Variations in Hypothalamic Monoamine Levels and Monoamine Oxidase Activity in the Teleost Channa Punctatus (Bloch)

In Channa punctatus, a significant daily variation in hypothalamic S-HT level and monoamine oxidase (MAO) activity was noticed in preparatory phase (February), but not in prespawning (May) or postspawning (November) phases. Hypothalamic dopamine (DA) and noradrenaline (NA), on the other hand, showed marked daily variation in their levels during all the three seasons with peak values in the photophase. The overall activity of MAO (mean ± SEM on 24-hr period) increased from November to May through February, whereas the 5-HT content which was high in November decreased during February and May. The NA and DA levels were low in November and Februry and high in May. The catecholamine (CA) content and MAO activity increased with increasing photoperiod and temperature which is indicative of an enhanced CA metabolism.     

Seasonal and Daily Variations in Hypothalamic Monoamine Levels and Monoamine Oxidase Activity in the Teleost Channa Punctatus (Bloch)

In Channa punctatus, a significant daily variation in hypothalamic S-HT level and monoamine oxidase (MAO) activity was noticed in preparatory phase (February), but not in prespawning (May) or postspawning (November) phases. Hypothalamic dopamine (DA) and noradrenaline (NA), on the other hand, showed marked daily variation in their levels during all the three seasons with peak values in the photophase. The overall activity of MAO (mean ± SEM on 24-hr period) increased from November to May through February, whereas the 5-HT content which was high in November decreased during February and May. The NA and DA levels were low in November and Februry and high in May. The catecholamine (CA) content and MAO activity increased with increasing photoperiod and temperature which is indicative of an enhanced CA metabolism.     

Circadian variations in plasma growth hormone and prolactin in the infant rat: Comparison with the adult pattern

Radioimmunoassayable (RIA) plasma growth hormone (GH) and prolactin (PRL) levels were determined at 3 hr intervals during a controlled 24-hr light-dark cycle in 10-day-old male and female rats; parallel measurements were made of brain monoamines (MA's), dopamine (DA), norepinephrine (NE) and serotonin (5-HT) concentration. Plasma GH and PRL and brain MA levels found in infant rats were compared to the same determinations made during the 24-hr cycle in 50-day-old male rats. GH levels were rather uniform and did not show circadian periodicity in the plasma of infant rats, while PRL levels showed a diurnal surge in the late afternoon hr (1800). In adult rats, GH levels exhibited wide fluctuations during the 24-hr cycle and no circadian periodicity, while PRL levels showed one diurnal (1500–1800) and one nocturnal (2400) surge. A pulsatile GH secretion was found in adult rats sampled at 15 min intervals over a period of 2 hr, which seemed to be lacking in infant rats. In the brain of infant rats, DA and NE levels exhibited circadian patterns which resembled the ones present in the brain of adult rats, whereas no circadian variations were present in 5-HT levels.     

Single doses of catecholamines in the rat: catecholaminotropic, but not hyperglycemic

1. As in two "lower" vertebrates, the lamprey and the eel, single intravascular injections of physiological doses (2.5 micrograms/kg) of epinephrine (E) into the rat immediately increased levels of plasma dopamine (DA) and norepinephrine (NE). 2. Single doses of DA (5 micrograms/kg) enhanced circulating NE and E, while NE (5 micrograms/kg) had no clear impact on the plasma levels of the other two catecholamines (CAs). 3. These data are at variance with findings in the eel, where all three CAs are mutually stimulatory; and in the lamprey, where only E stimulates release of the other two CAs. 4. It appears that E-stimulated CA release is widespread or ubiquitous among vertebrates, and that complex interactions between circulating CAs must be considered under experimental, physiological, and clinical conditions. 5. None of the injections had a significant hyperglycemic effect.     

Effects of Glycine on the Catecholamine Levels and Activities of Alcohol-Metabolizing Enzymes in Rats with Alcohol Intoxication and Addiction

We studied in rats the effects of peroral glycine introduction on the contents of catecholamines (CA) – noradrenaline (NA) and dopamine (DA) – in different brain structures (hypothalamus, midbrain, and neocortex), as well as the levels of adrenaline (A), NA, and DA in the blood and the activity of alcohol-metabolizing (AlM) enzymes – alcohol dehydrogenase (AlDH) and aldehyde dehydrogenase (AdhDH) – in the blood serum. The experimental group included animals with a disposition to alcohol consumption under conditions of free choice for drinking between an alcohol solution and water. The measurements were performed in animals in the state of acute alcohol intoxication (i.p. injection of 4 g/kg ethanol) or chronic alcohol addiction (formed due to a 3-month-long free access to ethanol solution). Introduction of 150 mg/kg glycine increased the NA and DA contents (the latter, to a lesser extent) in all examined brain structures; the NA level in the blood increased, while that of DA decreased. Under conditions of acute alcohol intoxication and chronic alcohol addiction, the ratio of the activities of AlM enzymes, AdhDH/AlDH, was significantly shifted toward values indicative of accumulation of acetaldehyde (AcAdh) in the tissues. This was accompanied by noticeable modifications of the CA contents in the brain structures and blood of the rats; in particular, the [DA]/[NA] ratio in the brain significantly increased. Introduction of glycine under conditions of acute alcohol intoxication provided normalization of the AdhDH/AlDH activity ratio. Obvious trends toward normalization of the CA levels in the brain structures were also observed in both acute and chronic experiments. In the latter case, the glycine treatment course resulted in a drop in the daily alcohol consumption by the animals. We conclude that glycine, which binds AcAdh and modifies the metabolism of CA transmitters, exerts a significant corrective influence on the pathogenetic mechanisms of alcohol addiction. Our experimental findings demonstrate that there are contact points between the acetaldehyde and catecholamine hypotheses of pathogenesis of alcoholism.     

Determinations of catechols in small volumes of plasma using ion-pair reversed phase liquid chromatography/electrochemistry

A method with improved sensitivity for detection of catechols (CA) in small volumes of plasma using an ion-pair reversed phase HPLC system with electromechemical detection is presented. Fast isocratic separations were obtained by using 7.5 cm x 4.6 mm (i.d.) reversed phase columns with 3C18 3 micron silica particles. The CA:s L-DOPA, Noradrenaline (NA), Adrenaline (A), Dihydroxybenzylamine (DHBA, i.s.), DOPAC and Dopamine (DA) were separated in less than 4 min. The performance of three different electrochemical cells was compared with respect to hydrodynamic voltammogram, band broadening effect, linearity and detection limit. The sample preparation procedure using alumina extraction of CA:s, was modified to improve recoveries and decrease dilution factors. A modified carbon paste cell (CP-O) gave a response 4-8 times higher than what is previously reported for GC cells. Detection limits were: L-DOPA 80, NA 1.25, A 1.25, DHBA 0.4, DOPAC 1.25 and DA 0.6 pg/injection. Application to plasma from rat and fish (cod) under rest, exercise and stress is reported. The method allows determination of CA:s in small volumes of plasma (less than 500 microliter) obtained several times a day from the same animal even if it is small (less than 1/2 kg), is under rest and parts of the plasma sample are to be used for analysis of other parameters than CA:s.     

Catecholamines inhibit neuronal activity in the glossopharyngeal-vagal motor complex of the Japanese eel: significance for controlling swallowing water

To clarify neuronal networks controlling swallowing water, inhibitory neurotransmitters were searched on the glossopharyngeal-vagal motor complex (GVC) of the medulla oblongata (MO), which is proposed as a motor nucleus controlling swallowing. Spontaneous firing (20-30 Hz) in the GVC was inhibited by adrenaline (AD), noradrenaline (NA) and dopamine (DA). The inhibitory effects of these catecholamines (CAs) were dose-dependent, and the effects of AD and NA were completely blocked by phenoxybenzamine or yohimbine, indicating that at least these two CAs act on the same receptor, presumably on alpha(2)-adrenoceptor. Even after blocking the alpha(2)-adrenoceptor with yohimbine, the inhibitory effect of DA still remained, indicating separate action of DA from AD or NA. Although DA receptor type was not determined in the present study, these results suggest existence of CA receptors in the GVC neurons. Almost 70% GVC neurons were inhibited by CAs. The CA-sensitive neurons were specifically restricted in the middle part of the GVC area. There were many tyrosine hydroxylase (TH)-immunoreactive somata and fibers in the eel MO. Among these TH-immunoreactive nuclei, the area postrema (AP) and the commissural nucleus of Cajal (NCC) appeared to project to the GVC morphologically. Significance of the catecholaminergic inhibition in the GVC activity is discussed in relation to controlling swallowing water.     

Differential effects of experimentally induced blood pressure changes on the release of catecholamines in hypothalamic and limbic areas of rats

The effects of longer lasting blood pressure changes on the release of endogenous catecholamines (CA) in limbic and hypothalamic areas were studied in anaesthetized rats. For this purpose the central nucleus of the amygdala (AC), ventral hippocampus (VH) and medial hypothalamus (MH) were simultaneously superfused through push-pull cannulae with artificial cerebrospinal fluid and the release of the endogenous catecholamines dopamine (DA), noradrenaline (NA) and adrenaline (A) was determined before and after blood pressure manipulations. A fall in blood pressure elicited by the ganglionic blocking agent chlorisondamine resulted in different changes of the various CA release patterns in AC. Short lasting increased CA release rates as compared to prehypotension levels could be observed in the hippocampus. The activity of catecholaminergic neurons in MH remained unchanged. A rise in arterial blood pressure induced by intravenous injection of tramazoline did not change the release rates of DA in all 3 brain areas studied. In hippocampus, NA levels in the superfusates decreased initially during hypertension but returned to normal values 40 min after drug injection. In the late phase of hypertension increased rates of release of NA in the amygdala and of A in the hypothalamus could be observed. The different patterns in the release of CA suggest that DA, NA and A are differentially implicated in the regulation of experimentally induced blood pressure changes.     

Effect of intracerebroventricularly administered insulin on brain monoamines and acetylcholine in euglycaemic and alloxan-induced hyperglycaemic rats.

There is now conclusive evidence for the presence of insulin and insulin receptors in the mammalian CNS and it has been postulated that they can modulate peripheral glucose homeostasis. Since a number of central neurotransmitters are also known to influence glucose levels and it is likely that CNS insulin receptors act through neurotransmitter mediation, the present study was conducted to investigate the effect of intracerebroventricularly (icv) administered insulin on rat brain dopamine (DA), noradrenaline (NA), serotonin and acetylcholine (ACh) activity in normal and alloxan-induced hyperglycaemic animals. Insulin was administered in doses (50 and 100 microU) which induced minimal hypoglycaemia, so as to obviate the likely effects of hypoglycaemia on neurotransmitter function. DA was estimated in midbrain-diencephalon (MD) and caudate nucleus (CN), NA and serotonin in MD and pons-medulla (PM), while ACh was estimated in all the three areas, namely, MD, CN and PM. The regional brain concentrations of DA, NA and serotonin were more in the hyperglycaemic rats as compared to their euglycaemic counterparts. However, the reverse was noted in case of ACh. Insulin induced a decrease in rat brain DA and NA levels, which was more marked in the hyperglycaemic animals. Conversely, insulin induced an increase in rat brain serotonin concentration which was not significantly different in normal and hyperglycaemic rats. Insulin induced marked increase in rat brain ACh levels, which was accentuated in hyperglycaemic animals. The present study reports for the first time the likely interaction between CNS insulin receptors and brain monoamines, and ACh, in euglycaemic and hyperglycaemic states.(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological aspects on catecholamine sampling

Catecholamine (CA) determinations are valuable tools in studies of sympatho-adrenal activity. However, several methodological problems should be considered when designing experiments and interpreting plasma CA results. The commonly assessed antecubital venous noradrenaline (NA) concentrations reflect local nerve activity, since about half of this NA is derived from the forearm tissues. Sympathetic nerve activity is not uniform, but may vary considerably between organs. Overall sympathetic activity is best assessed by measurements of NA in arterial or mixed venous blood. Venous adrenaline (ADR) levels may also be unrepresentative due to marked and variable extraction in the peripheral tissues. Urinary NA and ADR excretion studies still provide valuable information. Regional studies of NA overflow from individual organs give good estimates of local nerve activity and will increase the understanding of the functional organization of the sympathetic nervous system.     

Disturbances in catecholamine metabolism during formation and development of chronic alcoholism]

There has been carried out an investigation dealing with catecholamines metabolism in the patients suffering from alcoholism in the first, second and third stage at the short-term remission. The first developed alcoholism stage was determined as a typical one for increasing the excretion with urine of DOPA, dopamine (DA), noradrenaline (NA) and adrenaline (A), as well as the blood levels of DA, NA and A. DA/NA rate evidences about an increased synthesis of NA with DA. The marked second alcoholism stage is characterized by an acute decrease of excreting with urine and blood levels of NA. Alongside with the latter. DA excretion with urine and its blood levels remained high. DA/NA rate indicates to the considerably low relative activity of NA with DA synthesis, both in relation to the control and to the developed first alcoholism stage. In the third alcoholism stage NA excretion with urine and its blood levels become lower relatively to the marked second stage. Simultaneously DA excretion with urine and its blood levels are lower than in the developed second stage, hower exceed the control values. DA/NA rate testifies the slight activation of NA and DA synthesis. The results obtained in the work indicate to the significant role of CA metabolism disturbances in the alcoholic dependence formation.     

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.     

Effects of naloxone-precipitated withdrawal after a single dose of morphine on catecholamine concentrations in guinea-pig brain

The effect of naloxone-precipitated withdrawal after acute morphine was studied on the concentrations of noradrenaline (NA), 4-hydroxy-3-methoxyphenylethyleneglycol (MHPG), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and on the metabolite/parent amine ratios MHPG/NA, DOPAC/DA and HVA/DA, in eight regions of the guineapig brain. Guinea-pigs were treated with a single dose of morphine sulphate (15 mg/kg s.c.) or saline (control) and 2h later with naloxone hydrochloride (15 mg/kg s.c.) to precipitate withdrawal. The animals were decapitated at 0.5 h or 1 h after naloxone injections and their brains analysed for monoamine concentrations by HPLC-ECD. At 0.5 h after naloxone-precipitated withdrawal NA and MHPG levels, and the MHPG/NA ratio, were increased in the hypothalamus, and the NA levels were increased in the hypothalamus, medulla/pons and cortex 1 h after naloxone. Naloxoneprecipitated withdrawal also produced increased DA metabolism in the cortex, midbrain and medulla 0.5 h later, and in the cortex, hypothalamus and striatum 1 h later. Hence naloxone-precipitated withdrawal from acute morphine treatment produced a complex pattern of increased synthesis and metabolism of NA and DA which varied over time and with the brain region examined.     

Catecholamine content (as measured by the HPLC method) in brain and blood plasma of the eel: effects of 101 ATA hydrostatic pressure

The catecholamine content (noradrenaline, NA; adrenaline, A; dopamine, DA, and its metabolite, DOPAC) was measured, by the HPLC method, in brain and blood plasma of eels studied at atmospheric pressure (1 ATA) or at 101 ATA of hydrostatic pressure (HP). In the brain, HP induces a slight but significant increase (P less than 0.05) in A and DA contents but NA and DOPAC levels are not modified at 101 ATA when compared to 1 ATA. In the plasma, only A and NA are detected, adrenaline being the predominant amine. In eels exposed to 101 ATA HP, A and NA are strongly increased (+100%; P less than 0.01). The significance of the catecholamine increase in brain and plasma of the eels under HP is discussed.     

Seasonal changes in cardiovascular indices and monoamine content in the brain of rabbits

In our previous studies a rather substantial difference between the initial values of the cerebral blood flow was found. On the other hand the brain monoamine content varies in different months of the year when studied. Comparative analysis of these parameters in rabbit brain was the aim of this paper. The content of noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in cortical and subcortical structures and the local cerebral blood flow (ICBF), the systemic arterial pressure (SAP) and pulse rate (PR) were studied. There were found seasonal variations in all parameters. A certain LCBF retardation in subcortical structures and cortex and the weakest effect of the stimulation was observed in May. There was a drop in SAP and some PR increase in the spring (April-May). Brain NA and 5-HT content showed seasonal changes with the lowest values near the winter months and reaching maximum in May as the PR does. Content of DA was low in May. So it seams possible that the ion ICBF in May can be explained by the decrease of brain DA at that time. The ICBF and the reactivity of cerebral microvessels seem to depend on the monoamine content and show seasonal variability.     

Tissue catecholamine concentrations in spontaneously hypertensive rats

Tissue concentrations of noradrenaline (NA), dopamine (DA) and adrenaline (A) were compared in spontaneously hypertensive (SHR) and normotensive (NCR) rats, aged 1, 3, 8, 14 and 24 weeks The organs analyzed included the brain, subdivided into prosencephalon and rhombencephalon, heart, adrenal glands and kidney. Brain catecholamines were significantly lower in SHR than in NCR, and the difference appeared already at the age of 3 weeks. Concomitant increase was found in the adrenal NA and A concentrations of the SHR. Concentration of NA in the heart decreased in the SHR following onset of hypertension. It is concluded that the diminished NA, DA and A concentrations in the brain as well as the augmented adrenal NA and A levels in the SHR may be causally related to the development of hypertension, while the heart NA level reflects the secondary, hypertension -- related changes.     

Catecholaminotropic effects of catecholamines in a teleost fish,Anguilla rostrata

Summary Injections of physiological and supraphysiological doses of epinephrine (E) into cardiaccannulated eels cause a dose-related increase of plasma dopamine (DA) and norepineprine (NE) within 3 min. Likewise, both exogenous DA and NE increase the plasma titers of the respective other two catecholamines (CAs). The baseline titers of NE and E are closely correlated. Lack of a correlation of the baseline titers of NE and E with that of DA appears to be due to a faster disappearance rate of DA from the circulation. E is strongly hyperglycemic, and the weaker glycemic action of NE may be mediated via E release. The effects of E seem to depend on a spurt-like increase rather than its titer per se. The ability of the eel to cope with very fast, excessive increases of plasma CAs raises the question of the underlying mechanisms.Abbreviations CA(s) catecholamine(s) - DA dopamine - NE norepinephrine - E epinephrine     

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.