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  • 1
    Electronic Resource
    Electronic Resource
    Activation of α2-adrenoreceptors enhances haloperidol-induced suppression of operant behavior (1986)
    Springer
    Journal of neural transmission 66 (1986), S. 107-120 
    Details
    ISSN: 1435-1463
    Keywords: Rat ; behavior ; dopamine synthesis ; α 2-adrenoreceptor ; noradrenaline — dopamine interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Inhibition of catecholamine synthesis byα-methyl paratyrosine (α-MT) was previously shown to potentiate the behavioral suppression caused by dopamine-receptor antagonists. This effect ofα-MT is in all probability due to inhibition of the compensatory increase in dopamine turnover induced by the dopamine receptor antagonists. In the present study we investigated the effect of theα 2-adrenoreceptor agonist clonidine on the haloperidol-induced suppression of food-reinforced lever-pressing behavior (fixed ratio 40∶1) in rats. Small behaviorally inactive doses of clonidine were found, in analogy withα-MT, to enhance the haloperidol-induced suppression of the lever-pressing behavior. The haloperidol-induced increase in dopamine synthesis (measured as the accumulation of DOPA after inhibition of aromatic amino acid decarboxylare) was antagonized by clonidine in the striatum as well as in the dopamine rich limbic regions. Prazosin, a selectiveα 1-adrenoreceptor antagonist had no effect on the clonidine induced behavioral changes. Idazoxane, a selectiveα 2-adrenoreceptor antagonist, counteracted both the behavioral and biochemical effects of clonidine, indicating that these effects of clonidine are mediated via its action onα 2-adrenoreceptors. The present findings provide support for the notion thatα 2-adrenoreceptors may participate in the regulation of nigro-striatal as well as meso-limbic dopaminergic activity. It is suggested thatα 2-adrenoreceptor agents, especially in combination with classical antipsychotics, might be of therapeutic value in the treatment of disorders associated with abnormal dopaminergic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01260906
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  • 2
    Electronic Resource
    Electronic Resource
    Measurement ofJ/ψ and ψ′ real photoproduction on lithium-6 at a mean energy of 90 GeV (1987)
    Springer
    The European physical journal 33 (1987), S. 505-512 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Inelastic and elasticJ/ψ (3097) photoproduction on Li6 are measured at a mean γ energy of 90 GeV in an open spectrometer. TheJ/ψ are identified by their decays intoμ + μ − ore + e −. A signal of ψ′(3685) intoμ + μ − andJ/ψπ + π − is also seen. The inelastic cross-section withZ=E ψ/Eγ〈0.9 is compared in shape and magnitude with the colour singlet model of photon-gluon fusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01548261
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of clonidine on ultrasonic vocalization in preweaning rats (1988)
    Springer
    Journal of neural transmission 73 (1988), S. 217-237 
    Details
    ISSN: 1435-1463
    Keywords: Ultrasonic vocalization ; rat pups ; clonidine ; noradrenaline ; adreno-ceptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was undertaken to investigate the involvement of the noradrenergic neurotransmission system in the ultra sonic callings emitted by rat pups separated from their mother and exposed to cold stimulation. The investigation was primarily performed by help of agents selectively affecting the α-adrenoceptors: the α2-agonist clonidine, the α1-antagonist prazosin and the α2-antagonist idazoxan. Clonidine dose-dependently stimulated the amount of ultra sonic vocalization, an effect not solely dependent upon the effect of clonidine on body temperature. In a developmental study it was found that clonidine uniformly stimulated crying at all ages from 4 days of age up to 18 days of age, that is during the whole preweaning period. Clonidine stimulated ultrasonic crying in rat pups, devoid of presynaptic catecholamine (CA) neurons by combined pretreatment with the monoamine depletor, reserpine, and the inhibitor of CAsynthesis, α-methyl-tyrosine. This finding suggested that the stimulating effect of clonidine on ultrasonic vocalization was mediated by postsynaptic adrenoceptors. In pups, 12 days of age, idazoxan blocked the effect of cold stimulation on ultra sonic crying, suggesting that α2-adrenoceptors, presumably postsynaptic ones, mediated this kind of stimulation. Idazoxan also antagonized the effect of clonidine, but only at a dose effective also in control pups. Prazosin had no effect on cold-stimulated crying, but antagonized the effect of clonidine, suggesting that the effect of clonidine was also mediated by α1-receptors. At 18 days of age, prazosin no longer antagonized the effect of clonidine, whereas the antagonizing action of idazoxan was reinforced. The age-dependent variation in responsiveness to the adrenergic drugs suggest maturational changes in the function of the CA-system occurring between 12–16 days of age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01250138
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  • 4
    Electronic Resource
    Electronic Resource
    Biochemical and behavioral evidence for an interaction between ethanol and calcium channel antagonists (1988)
    Springer
    Journal of neural transmission 74 (1988), S. 181-193 
    Details
    ISSN: 1435-1463
    Keywords: Ethanol ; nifedipine ; calcium channels ; locomotor activity ; preference ; dopaminergic activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present series of experiments we have studied the effects of the dihydropyridine calcium channel antagonist nifedipine on ethanol-induced changes in behavior and dopamine (DA) release and metabolism. The locomotor-stimulatory effect of low doses of ethanol (2.5 g/kg) was antagonized by nifedipine, whereas ethanol-induced sedation observed after higher doses (4.5 g/ kg) was potentiated. Biochemical studies indicated that ethanol enhanced the metabolism and release of DA in the striatum and the DA-rich limbic regions measured by post mortem analyses of DA-metabolites by HPLC with electrochemical detection and by in vivo voltammetry in anaesthetized rats, respectively. Pretreatment with nifedipine antagonized the stimulatory effects of ethanol on the DA-system. Nifedipine reduced the preference for ethanol, estimated by the relative intake of ethanol (6% v/v) and water in a free-choice situation, suggesting an influence of nifedipine not only on the stimulatory but also on the positive reinforcing effects of ethanol. The present results suggest that the locomotor-stimulatory and positive reinforcing effects of ethanol as well as its enhancing effect on dopaminergic activity may involve an enhancement of calcium mediated mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244784
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  • 5
    Electronic Resource
    Electronic Resource
    Possible involvement of noradrenergic descending pain-modulating pathways in the mode of antinociceptive action of flupirtine, a novel non-opioid analgesic (1988)
    Springer
    Inflammation research 23 (1988), S. 112-116 
    Details
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract These experimental studies were conducted to obtain information about the antinociceptive action of flupirtine within the central nervous system. Flupirtine dose-dependently increased pain threshold in the electrostimulated pain test in mice. Its antinociceptive activity was attenuated by simultaneous administration of the noradrenergica 1/a 2-antagonist yohimbine anda 2-antagonist idazoxane. By contrast, the analgesia induced by codeine or morphine was not influenced bya 2-adrenergic antagonists at all. A striking resemblance could be observed in the pharmaco-EEG of freely moving rats treated with clonidine and flupirtine, respectively. The present results are consistent with the hypothesis that the noradrenergic descending pain-modulating system might be involved in the antinociceptive mode of action of flupirtine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01967209
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  • 6
    Electronic Resource
    Electronic Resource
    Ester derivatives of the mammary-tumor-inhibiting antiestrogen 2,3-bis(2-fluoro-4-hydroxyphenyl)-2,3-dimethylbutane (1989)
    Springer
    Journal of cancer research and clinical oncology 115 (1989), S. 161-165 
    Details
    ISSN: 1432-1335
    Keywords: 2,3-Bis(2-fluoro-4-hydroxyphenyl)-2,3-dimethylbutane ; Synthesis of their ester derivatives ; Partial antiestrogens ; Estrogen receptor affinity ; Mammary-tumor-inhibiting activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The synthesis of the bisacetate (8), the bisdichloroacetate (9), the biscarbamate (10) and the bisphosphate (11) of the “partial” antiestrogen 2,3-bis(2-fluoro-4-hydroxyphenyl)-2,3-dimethylbutane (7) is described. In the case of 8–10 the introduction of ester functions slightly reduces the estrogen receptor affinity of 7. However, it was strongly diminished in 11. Compared with 7 the estrogenic potency of 8–11 is moderately increased. Compounds 8–11 cause a strong inhibition of the hormone-dependent MXT M3.2 mouse mammary tumor. Only 9 containing cytotoxic dichloroacetate groups shows a significantly better antitumor effect than 7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397917
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  • 7
    Electronic Resource
    Electronic Resource
    Anxiolytic-like action of the 3-PPP enantiomers in the Vogel conflict paradigm (1987)
    Springer
    Psychopharmacology 92 (1987), S. 371-375 
    Details
    ISSN: 1432-2072
    Keywords: 3-PPP enantiomers ; Vogel test ; Anti-conflict ; “Pro”-conflict ; Dopamine (DA) ; Anxiety
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of the (+)- and (-)-enantiomers of 3-PPP [conventional and atypical dopamine (DA)-receptor active agent, respectively] were investigated in a commonly used animal model of anxiety: the Vogel licking-conflict test. Low doses (≤0.5 mg/kg SC) of both 3-PPP enantiomers resulted in anti-conflict (=anxiolytic-like) actions in this test. (-)-3-PPP proved to be almost as potent as apomorphine in releasing the punished responding (minimum effective doses; (-)-3-PPP: 0.016, and apomorphine: 0.006 mg/kg SC), whereas (+)-3-PPP was about 10 times less effective than apomorphine. In the higher dose range (≥1.0 mg/kg), both 3-PPP enantiomers instead induced an apparent “pro”-conflict effect; i.e. decreased responding to a level significantly below baseline, thus resulting in a biphasic dose-response curve. Simple alterations in the animals' motivation to drink, in shock threshold or in motor capabilities did not seem to be major explanatory factors either for the anti- or for the “pro”-conflict effects. With regard to the latter, the possibility is discussed of an interaction between the experimental test situation and non conflict-related effects of the drugs, thus interfering with the punished drinking. The findings are interpreted within the concept that low doses of the 3-PPP enantiomers, in particular (-)-3-PPP, may attenuate anxiety-elicited increases in the neurotransmission in certain meso-cortical/limbic DA pathways, i.e. consistent with the previously shown preferentially “limbic” net antidopaminergic profile of action of (-)-3-PPP. The results support an active role for DA in conditions associated with anxiety and reinforce the view that novel putative anxiolytics might be found among selective DA-modulating agents like, e.g. the atypical DA receptor agonist (-)-3-PPP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00210846
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  • 8
    Electronic Resource
    Electronic Resource
    Biphasic effect of l-5-HTP in the Vogel conflict model (1987)
    Springer
    Psychopharmacology 92 (1987), S. 96-99 
    Details
    ISSN: 1432-2072
    Keywords: 5-HT ; l-5-HTP ; Anxiolytic ; Anxiogenic ; Drinking ; Conflict ; Vogel test ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of l-5-HTP (25–400 mg/kg IP) following inhibition of the peripheral aromatic amino acid decarboxylase by means of benserazide (25 mg/kg IP) was investigated in a test modified from Vogel's drinking conflict model. At 50 mg/kg an anti-conflict action was detected, while higher doses (100–400 mg/kg) decreased punished responding. A lower dose (25 mg/kg) had no effect. Non-specific effects — such as alterations in muscle tone, in motivation to drink or in the sensitivity to electrical shock — could not explain the anxiolytic- and anxiogenic-like actions of 50 and 100 mg/kg, respectively. The bi-phasic effect of l-5-HTP is discussed in terms of different subpopulations of central serotoninergic receptors, possibly exerting opposing influences on conflict responding. The study emphasises the importance of 5-HT mechanisms in anxiety, and the possibility of finding novel anxiolytics among drugs selectively affecting central 5-HT neurotransmission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215486
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  • 9
    Electronic Resource
    Electronic Resource
    Some characterizations of distributions by regression models for ordinal response data (1985)
    Springer
    Metrika 32 (1985), S. 65-72 
    Details
    ISSN: 1435-926X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Summary Let a random variableX be classified intok classes. By doing so, a new random variable is obtained, measured on ordinal scale. If this variable is a response variable in certain regression models for ordinal response data, the distribution ofX is characterized by the models. In this paper, characterizations of the distribution ofX by the proportional odds model and the proportional hazards model are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01897801
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  • 10
    Electronic Resource
    Electronic Resource
    Does the PCPA induced anticonflict effect involve activation of the GABAA/benzodiazepine chloride ionophore receptor complex? (1989)
    Springer
    Journal of neural transmission 76 (1989), S. 145-153 
    Details
    ISSN: 1435-1463
    Keywords: Anxiolytic-like effect ; bicuculline ; flumazenil ; GABAA/benzodiazepine receptor-serotonin interaction ; PCPA ; rat ; Vogel's conflict model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of the benzodiazepine (BDZ) receptor antagonist flumazenil (Ro 15-1788) and the GABAA receptor antagonist bicucuiline on the anticonflict effect observed after depletion of brain serotonin (5-HT), were examined in a modified Vogel's punished drinking conflict model. Pretreatment with para-chlorophenylalanine (PCPA; 300 mg/kg/day for three days, last injection −24 h) markedly decreased brain 5-HT levels and produced clearcut anticonflict effects. The anticonflict effect, but not the biochemical effect, of PCPA pretreatment was completely counteracted by both flumazenil (10 mg/ kg, −30 min) and bicuculline (2.0 mg/kg, −10 min), in doses not altering the behavior per se. The findings suggest a behavioral interaction between 5-HT systems and the GABAA/BDZ chloride ionophore receptor complex, possibly involving a direct neuronal interaction, neuromodulation or hormonal alterations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578754
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