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  • 1
    Electronic Resource
    Electronic Resource
    Effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on tryptophan and glucose homeostasis in the most TCDD-susceptible and the most TCDD- resistant species, guinea pigs and hamsters (1995)
    Springer
    Archives of toxicology 69 (1995), S. 677-683 
    Details
    ISSN: 1432-0738
    Keywords: Key words 2 ; 3 ; 7 ; 8-Tetrachlorodibenzo-p-dioxin ; Species differences ; Acute toxicity ; Serotonin ; Tryptophan ; Gluconeogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We have previously reported that in rats 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) lethality is associated (although not necessarily causally) with changes in brain serotonin (5-HT) metabolism. In the present study, we have examined whether this holds for other species by comparing the effect of TCDD in the most TCDD-susceptible and the most TCDD-resistant species, guinea pigs and hamsters, respectively. Body weight gain of guinea pigs exposed to TCDD (0.3–2.7 μg/kg) diminished dose dependently, while the effect was marginal in hamsters (900–4600 μg/kg). Brain 5-hydroxyindoleacetic acid (the main metabolite of brain 5-HT), brain tryptophan (the precursor amino acid of 5-HT), and plasma free and total tryptophan were not affected at any dose in guinea pigs. In contrast, 4 days after exposure, the levels of plasma free and total tryptophan were consistently increased in hamsters. These, as well as brain tryptophan, were still elevated 10 days after exposure. TCDD did not affect plasma glucose level in either species. Liver glycogen was decreased in a dose-dependent manner in TCDD-treated guinea pigs as well as in their pair-fed controls on day 10. There was no change in liver glycogen in hamsters. The activity of the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase was only depressed in hamsters by all doses of TCDD. We conclude that changes in tryptophan metabolism or in carbohydrate homeostasis cannot explain the wide interspecies differences in susceptibility to the acute lethality of TCDD, although they may correlate with some aspects of its toxicity in certain species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050231
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on biogenic amines and their acidic metabolites in brain and cerebrospinal fluid of rats (1989)
    Springer
    Archives of toxicology 63 (1989), S. 127-130 
    Details
    ISSN: 1432-0738
    Keywords: 2,4-Dichlorophenoxyacetic acid ; Biogenic amines ; Brain ; Cerebrospinal fluid ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Effects of single subcutaneous doses of sodium 2,4-dichlorophenoxyacetate (2,4-D-Na) on biogenic amines and their acidic metabolites in rat brain and cerebrospinal fluid (CSF) were analyzed by high pressure liquid chromatography. After 200 mg/kg 2,4-D-Na, the cerebral concentration of 5-hydroxytryptamine (5-HT) was increased slightly and that of 5-hydroxyindoleacetic acid (5-HIAA) roughly 3-fold between 1 and 8 h after the administration. There was also a tendency towards slightly lowered dopamine (DA) levels. No statistically significant changes in brain concentrations of noradrenaline (NA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) or tryptophan (TRY) were found. At the same time, however, the maximal increase in DOPAC, HVA and 5-HIAA concentrations in the CSF was 2.3–5.8-fold. The dependency of biogenic amines and metabolites on 2,4-D-Na dose was studied by injecting s.c. 0, 10, 30 and 100 mg/kg and sacrificing the rats at 2 h. In the brain, there was a dose-dependent increase in concentrations of 5-HIAA (at the two highest doses) and HVA (at the highest dose) while in the CSF those of all three acidic metabolites increased at the two highest doses. The 10 mg/kg dose had no effect. The results agree with the hypothesis that 2,4-D inhibits the organic acid transport out of the brain, which should then result in increased cerebral levels of acidic metabolites of biogenic amines, but it may also have effects on the activity of serotoninergic and dopaminergic neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316434
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  • 3
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    Unknown
    Father Roderick MacDonnell, Missionary At St. Regis and the Glengarry Catholics. (1933)
    Washington : Periodicals Archive Online (PAO)
    Catholic historical review. 19 (1933/1934) 265 
    Details
    ISSN: 0008-8080
    Topics: History , Theology and Religious Studies
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:1053-1933-019-00-000007
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of the effects of acute and subchronic administration of atipamezole on reaction to novelty and active avoidance learning in rats (1999)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 359 (1999), S. 194-203 
    Details
    ISSN: 1432-1912
    Keywords: Key words Atipamezole ; α2-Adrenoceptor antagonism ; Learning ; Noradrenaline ; Stress ; Subchronic treatment ; Behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of an α2-adrenoceptor antagonist, atipamezole, on exploratory behaviour in a novel environment, spontaneous motor activity and active avoidance learning were studied after acute injection and continuous infusion (0.1 mg/kg h) for 24 h and 6–9 days in rats. The effects of atipamezole on biogenic amines and their main metabolites in brain were studied after an acute injection (0.3 mg/kg s.c.) and continuous infusion (0.1 mg/kg h) for 24 h and 10 days. The level of central α2-adrenoceptor antagonism and the drug concentration in blood and in the brain were measured after continuous infusion for 24 h and 10 days. In behavioural tests, atipamezole had no effect on spontaneous motor activity at any of the doses studied. However, after both acute administration and continuous 24-h infusion, atipamezole decreased exploratory behaviour in a staircase test, but no longer after 6 days of continuous infusion. Acute administration of atipamezole impaired performance in active avoidance learning tests causing a learned helplessness-like behaviour. When the training was started after 7 days of continuous infusion, atipamezole significantly improved active avoidance learning. There was a significant increase in the metabolite of noradrenaline (NA), 3-methoxy-4-hydroxyphenylethyleneglycol sulphate (MHPG-SO4), after 24 h but not any longer after 10 days of continuous atipamezole infusion, although the extent of central α2-adrenoceptor antagonism was unchanged and the atipamezole concentration present in brain was even elevated at 10 days compared to levels after 24-h infusion. In conclusion, these results reveal that acute and sub-chronic atipamezole treatments have different and even opposite effects on behaviour in novel, stressful situations. After acute treatment, atipamezole potentiates reaction to novelty and stress, causing a decrease in exploratory activity and impairment in shock avoidance learning. After subchronic treatment, there was no longer any effect on exploratory behaviour and, in fact, there was an improvement in the learning of a mildly stressful active avoidance test. The changes in behaviour occurred in parallel with attenuation in the MHPG-SO4-increasing effect, thus the suppressed behaviour in the present test conditions after acute atipamezole injection is associated with a major increase in central NA release. The results support the role of α2-adrenoceptors and noradrenergic system in reactions both to novelty and stress and have possible implications in cognitive functions as well as in depression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005342
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of the effects of a specific α2-adrenoceptor antagonist, atipamezole, on α1- and α2-adrenoceptor subtype binding, brain neurochemistry and behaviour in comparison with yohimbine (1997)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 356 (1997), S. 570-582 
    Details
    ISSN: 1432-1912
    Keywords: Key words Atipamezole ; α2-adrenoceptor subtypes ; α2D-adrenoceptor ; Hypothermia ; Monoamines ; Noradrenergic neurons ; Sedation ; Yohimbine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present study we evaluated the α1- and α2-adrenoceptor subtype binding, central α2-adrenoceptor antagonist potency, as well as effects on brain neurochemistry and behavioural pharmacology of two α2-adrenoceptor antagonists, atipamezole and yohimbine. Atipamezole had higher selectivity for α2- vs. α1-adrenoceptors than yohimbine regardless of the subtypes studied. Both compounds had comparable affinity for the α2A-, α2C- and α2B-adrenoceptors, but yohimbine had significantly lower affinity for the α2D-subtype. This may account for the fact that significantly higher doses of yohimbine than atipamezole were needed for reversal of α2-agonist (medetomidine) -induced effects in rats (mydriasis) and mice (sedation and hypothermia). The effect on central monoaminergic activity was estimated by measuring the concentrations of transmitters and their main metabolites in whole brain homogenate. At equally effective α2-antagonising doses in the rat mydriasis model, both drugs stimulated central noradrenaline turnover (as reflected by increase in metabolite levels) to the same extent. Atipamezole increased dopaminergic activity only slightly, whereas yohimbine elevated central dopamine but decreased central 5-hydroxytryptamine turnover rates. In behavioural tests, atipamezole (0.1–10 mg/kg) did not affect motor activity but stimulated food rewarded operant (FR-10) responding (0.03–3 mg/kg) whereas yohimbine both stimulated (1 mg/kg) and decreased (≥ 3 mg/kg) behaviour in a narrow dose range in these tests. In the staircase test, both antagonists increased neophobia, but in the two compartment test only yohimbine (≥ 3 mg/kg) decreased exploratory behaviour. The dissimilar effects of the antagonists on neurochemistry and behaviour are thought to be caused by non α2-adrenoceptor properties of yohimbine. In conclusion, the α2-antagonist atipamezole blocked all α2-adrenoceptor subtypes at low doses, stimulated central noradrenergic activity and had only slight effects on behaviour under familiar conditions, but increased neophobia. The low affinity for the α2D-adrenoceptor combined with its unspecific effects complicates the use of yohimbine as pharmacological tool to study α2-adrenoceptor physiology and pharmacology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00005092
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  • 6
    Electronic Resource
    Electronic Resource
    Additive deficits in the choice accuracy of rats in the delayed non-matching to position task after cholinolytics and serotonergic lesions are non-mnemonic in nature (1997)
    Springer
    Psychopharmacology 130 (1997), S. 303-312 
    Details
    ISSN: 1432-2072
    Keywords: Key words Working memory ; Motor activity ; Serotonergic ; Muscarinic ; Nicotinic ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of serotonin (5-HT) and its interaction with the muscarinic or nicotinic receptor-mediated mechanisms in the modulation of working memory and motor activity was investigated by assessing the effects of 5-HT lesion and cholinergic receptor blockade on the performance of rats in a working memory (delayed non-matching to position, DNMTP) task. A global serotonergic lesion was induced by the intracerebroventricular adminstration of 5,7-dihydroxytryptamine (5,7-DHT). Post-mortem neurochemical analysis revealed that serotonin and 5-hydroxyindoleacetic acid (5-HIAA) levels were reduced in frontal and parieto-occipital cortices and in hippocampi of 5,7-DHT lesioned rats. 5-HIAA levels were also reduced in striatum. 5,7-DHT lesion slightly impaired choice accuracy of rats in the DNMTP task and also transiently reduced motor activity in rats. Even the lower dose of scopolamine (0.075 mg/kg), a muscarinic receptor antagonist, impaired the choice accuracy already at the shortest delay (i.e. not indicative of a working memory impairment per se), and caused a marked disruption of motor activity (lengthened response latencies, increased probability of omissions and decreased trials completed). Furthermore, the quaternary analogue, N-methylscopolamine (0.150 mg/kg), affected the motor activity of rats to the same extent as scopolamine. Mecamylamine (1.0; 3.0 mg/kg) also interfered with motor activity and it slightly decreased the choice accuracy, which was not dependent on the delay. Although mecamylamine disrupted the performance of rats in the DNMTP task, the disruption was not as severe as that seen with scopolamine. Moreover, both scopolamine and mecamylamine augmented the slight impairment on the choice accuracy of 5,7-DHT lesioned rats, but this was non-mnemonic in character. We conclude that there is no evidence for any major interaction between the serotonergic system and muscarinic or nicotinic cholinergic mechanisms in working memory per se, but muscarinic and nicotinic receptor antagonists may act additively with the 5,7-DHT lesion to disrupt the choice accuracy of rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050244
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  • 7
    Electronic Resource
    Electronic Resource
    Plasma catecholamine and serum testosterone responses to four units of resistance exercise in young and adult male athletes (1998)
    Springer
    European journal of applied physiology 77 (1998), S. 413-420 
    Details
    ISSN: 1439-6327
    Keywords: Key words Catecholamines ; Testosterone ; Resistance exercise ; Age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The plasma noradrenaline (NA) and adrenaline (A) concentration responses of seven young male athletes [15 (SD 1) years] and seven adult male athletes [25 (SD 6) years] were investigated together with the serum testosterone (Tes) concentration responses in four different half-squatting exercises. The loads, number of repetitions, exercise intensity and recovery between the sets were manipulated such that different types of metabolic demand could be expected. However, the amount of work done was kept equal in each kind of exercise. After the most exhausting unit of exercise (E3; two sets of 30 repetitions with 50% of 1 repetition maximum and with 2-min recovery between the sets) the plasma NA concentration was significantly lower in the younger than in the adult subjects [15.7 (SD 7.8) vs 32.7 (SD 13.2) nmol · l−1, P 〈 0.05], while the A concentrations were similar. In the other three exercises no differences in the plasma catecholamine concentration responses among the groups were observed. The postexercise Tes concentrations, however, were significantly lower in the younger than in the adult subjects in every exercise unit. No correlations between the plasma catecholamine and serum Tes concentration responses were observed in any of the exercise units in either group. The results of the present study may suggest reduced sympathetic nervous activity in the younger subjects compared to the adults in response to exhausting resistance exercise. The results may also suggest that the catecholamines were less involved in eliciting an increase in Tes secretion in these resistance exercises.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050353
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  • 8
    Electronic Resource
    Electronic Resource
    Plasma catecholamine responses to four resistance exercise tests in men and women (1999)
    Springer
    European journal of applied physiology 80 (1999), S. 125-131 
    Details
    ISSN: 1439-6327
    Keywords: Key words Catecholamines ; Resistance exercise ; Electromyography ; Sex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The plasma adrenaline ([A]) and noradrenaline ([NA]) concentration responses of nine men and eight women were investigated in four resistance exercise tests (E80, E60, E40 and E20), in which the subjects had to perform a maximal number of bilateral knee extension-flexion movements at a given cycle pace of 0.5 Hz, but at different load levels (80%, 60%, 40% and 20% of 1 repetition maximum, respectively). The four test sessions were separated by a minimal interval of 3 rest days. The number of repetitions (Repmax), the total work (W tot) done normalized for the lean body mass and the heart rate (HR) responses were similar in the two groups in each test. In addition, no differences were found between the two groups in [A] and [NA] either before or after the exercise tests. The postexercise [NA], both in the men [10.8 (SD 7.0) nmol · l−1] and in the women [11.7 (SD 7.4) nmol · l−1], was clearly the highest in E20, where also the Repmax, W tot, the total amount of integrated electromyograph activity in the agonist muscles and the peak postexercise blood lactate concentration [men 8.3 (SD 1.6) vs women 7.3 (SD 0.9) mmol · l−1, ns] were significantly higher than in the other tests. Although the postexercise [A] in E20 both in the men [7.1 (SD 6.0) nmol · l−1] and in the women [5.2 (SD 2.0) nmol · l−1] were higher than in E80 [men 3.1 (SD 4.2), women 2.1 (SD 2.0) nmol · l−1] (P 〈 0.05), they were not significantly different from E60 [men 3.6 (SD 1.9), women 4.0 (SD 3.3) nmol · l−1] and E40 [men 3.8 (SD 4.1), women 5.8 (SD 4.0) nmol · l−1] in either group. The present study did not indicate any sex differences in performance and in plasma catecholamine responses in different exhausting resistance exercise tests performed with the knee extensor muscles. In both groups the plasma [NA] response was clearly the largest in the longest exercise with the greatest amount of muscle activity and work done, and with the largest blood lactate response. The differences in the plasma [A] responses between the exercises tended to be somewhat smaller.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050568
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