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  • 1
    Electronic Resource
    Electronic Resource
    Local Activation of Metabotropic Glutamate Receptors Inhibits the Handling-Induced Increased Release of Dopamine in the Nucleus Accumbens but Not that of Dopamine or Noradrenaline in the Prefrontal Cortex: Comparison with Inhibition of Ionotropic Receptors (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: On-line in vivo microdialysis was used to determine the effects of a 16-min handling period on release of dopamine (DA) in the nucleus accumbens and of DA and noradrenaline (NA) in the medial prefrontal cortex of awake, freely moving rats. DA and NA were determined in one HPLC run. Handling resulted in an immediate and strong increase of both catecholamines in the prefrontal cortex. Maximal values for DA were 295%, and for NA 225%, of controls. DA in the nucleus accumbens was also increased (to 135% of controls) but only after a short delay. Local inhibition of ionotropic glutamate receptors by continuous reversed dialysis of the drugs 6-cyano-7-nitroquinoxaline, d-2-amino-5-phosphonopentanoic acid, or dizocilpine did not significantly affect handling-induced increases in cortical DA and NA release. Neither did the agonist of metabotropic glutamate receptors, trans-(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), or the GABA-B agonist baclofen. Reversed dialysis of dizocilpine in the nucleus accumbens was equally ineffective, but ACPD inhibited the increase in DA release in this area. Stimulation of metabotropic glutamate receptors in the nucleus accumbens was previously reported to inhibit activation of DA release in that area after stimulation of glutamatergic or dopaminergic afferents. It is concluded that metabotropic receptors in the nucleus accumbens are important for the control of activation of DA release in the accumbens by physiological stimuli but that a similar mechanism is lacking in the prefrontal cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.70031104.x
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  • 2
    Electronic Resource
    Electronic Resource
    Anatomical and functional demonstration of a multisynaptic suprachiasmatic nucleus adrenal (cortex) pathway (1999)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In view of mounting evidence that the suprachiasmatic nucleus (SCN) is directly involved in the setting of sensitivity of the adrenal cortex to ACTH, the present study investigated possible anatomical and functional connections between SCN and adrenal. Transneuronal virus tracing from the adrenal revealed first order labelling in neurons in the intermedio-lateral column of the spinal cord that were shown to receive an input from oxytocin fibres and subsequently second-order labelling in neurons of the autonomic division of the paraventricular nucleus. The latter neurons were shown to receive an input from vasopressin or vasoactive intestinal peptide (VIP) containing SCN efferents. The true character of this SCN input to second-order neurons was also demonstrated by the fact that third-order labelling was present within the SCN, vasopressin or VIP neurons. The functional presence of the SCN–adrenal connection was demonstrated by a light-induced fast decrease in plasma corticosterone that could not be attributed to a decrease in ACTH. Using intact and SCN-lesioned animals, the immediate decrease in plasma corticosterone was only observed in intact animals and only at the beginning of the dark period. This fast decrease of corticosterone was accompanied by constant basal levels of blood adrenaline and noradrenaline, and is proposed to be due to a direct inhibition of the neuronal output to the adrenal cortex by light-mediated activation of SCN neurons. As a consequence, it is proposed that the SCN utilizes neuronal pathways to spread its time of the day message, not only to the pineal, but also to other organs, including the adrenal, utilizing the autonomic nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.1999.00575.x
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  • 3
    Electronic Resource
    Electronic Resource
    S(−)DP-5,6-ADTN as an in vivo dopamine receptor ligand: Relation between displacement by dopamine agonists and their pharmacological effects (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 332 (1986), S. 338-345 
    Details
    ISSN: 1432-1912
    Keywords: (−)DP-5,6-ADTN ; DP-7-OH-ATN ; NPA ; Bromocriptine ; 3-PPP ; HVA ; Stereotypy ; In vivo DA receptor binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The use of (−)DP-5,6-ADTN as a non-radio-actively labeled ligand for an in vivo DA receptor assay is described and compared with racemic DP-5,6-ADTN, previously used for that purpose. The effects of four DA agonists (NPA, bromocriptine, DP-7-OH-ATN and 3-PPP) on the specific (−)DP-5,6-ADTN binding are related to their potencies to decrease striatal HVA concentrations and to induce stereotypy in rats. NPA and DP-7-OH-ATN caused a maximal decrease in HVA levels, when only a fraction of the receptors were occupied, while the occurrence of stereotypy was associated with a high receptor occupation, reflecting the higher affinity of these agonists for presynaptic than for postsynaptic receptors. Bromocriptine did not show this effect, as the dose-response relationships for HVA decrease, for induction of stereotypy and for the decrease in specific (−)DP-5,6-ADTN binding were all virtually equal to each other. While NPA and bromocriptine behaved as full postsynaptic agonists, in that maximal stereotyped behavior was observed after high doses, DP-7-OH-ATN was found to be a partial postsynaptic agonist, as it did not induce maximal stereotypy at a maximal receptor occupation. Racemic 3-PPP only caused a state of hypoactivity, but did neither affect specific (−)DP-5,6-ADTN binding nor striatal HVA levels. Our results are discussed in view of theories on the relation between receptor occupation and pharmacological effects and it is concluded that the in vivo receptor binding method using (−)DP-5,6-ADTN is a very useful tool for such investigations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500084
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  • 4
    Electronic Resource
    Electronic Resource
    Early postnatal clonidine treatment results in altered regional catecholamine utilisation in adult rat brain (1992)
    Springer
    Psychopharmacology 106 (1992), S. 19-25 
    Details
    ISSN: 1432-2072
    Keywords: Brain development ; Clonidine ; Noradrenaline utilisation ; Dopamine utilisation ; Functional teratology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Clonidine is a clinically used antihypertensive which has been suggested to produce physiological changes in children after exposure in utero. The aim of our study was to test the hypothesis that chronic exposure of the developing brain to an α2-adrenergic agonist like clonidine would influence the adult neurochemical setting of central monoamine neurotransmitter systems. Male rat pups were treated from postnatal day 8 to 21 twice daily with saline or with 0.1 mg/kg clonidine. After the last injection on day 21, brain regional catecholamine utilisation was determined using synthesis inhibition with α-methyl-p-tyrosine in a subgroup of the pups. The expected decrease in noradrenaline utilisation after clonidine was observed, although statistical significance was not reached in a number of brain regions. Dopamine utilisation was not affected. The other pups were left to reach young adulthood and catecholamine utilisation was measured on day 90. Noradrenaline utilisation on day 90 was significantly decreased in two regions: the medulla-pons and the mesolimbic (dopamine projection) areas. Dopamine utilisation was decreased in the hypothalamus and increased in the amygdala and the cerebellum. These adult neurochemical alterations corroborate previous findings of adult behavioural, physiological and central biochemical alterations in rats exposed to clonidine in early postnatal life.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02253583
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  • 5
    Electronic Resource
    Electronic Resource
    Brain and serum concentrations of dopamine analogues after peripheral administration to rats (1984)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 326 (1984), S. 203-209 
    Details
    ISSN: 1432-1912
    Keywords: Dopamine analogues ; Catechol-O-methyl transferase ; Brain concentrations ; Partition coefficients ; N,N-dipropyldopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Concentrations of dopamine (DA) analogues were determined in rat brain regions and serum after peripheral administration of the drugs. The time course of the concentrations of four N,N-dialkylated DA derivatives is reported in relation to the simultaneously measured effects on DA metabolism. Maximum brain concentrations were reached at about 10 min after injection, followed by a rapid elimination of the parent compounds. O-Methylation was found to be of major importance in this early disappearance. The 3-O-methyl metabolite of N,N-dipropyl-DA (DiPr-DA) was very rapidly formed and was eliminated much more slowly than the parent compound. Inhibition of O-methylation as well as subcutaneous, instead of intraperitoneal (ip), administration resulted in higher brain and serum levels of DiPr-DA. Brain concentrations of 11 DA analogues were determined 10 min after ip injection and were compared with their octanol/water (pH 7.4) partition coefficients. Within one group of compounds with a similar metabolic profile the brain concentrations and partition coefficients showed a good correlation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00505319
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of dihydroxy-2-aminotetralin derivatives on dopamine metabolism in the rat striatum (1980)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 310 (1980), S. 219-225 
    Details
    ISSN: 1432-1912
    Keywords: Dihydroxyaminotetralins ; Apomorphine ; Prodrugs ; Striatum ; Dopamine metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Concentrations of dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured in the striatum of rats after i.p. injection of apomorphine, N,N-dipropyldopamine and a series of alkylated and/or esterified dopamine analogues of the dihydroxyaminotetralin type. All compounds tested caused a decrease in DOPAC- and HVA-concentrations. The N-alkylated derivatives had a rapid onset of action, showing a maximal HVA decrease after 15–45 min, after which time the metabolite concentrations slowly returned to control values. In addition, the dihydroxyaminotetralins, especially N,N-dipropylamino-5,6-dihydroxytetrahydronaphthalene (DiPr-5,6-ADTN), produced a rapid, short lasting elevation of DA concentrations. The esterified primary amines, dibenzoyl-5,6-and dibenzoyl-6,7-dihydroxyaminotetralin, had a delayed effect, causing a maximal HVA decrease after 4–6 h. DiPr-5,6-ADTN was found to be the most potent compound, with a maximal effect at a dose of 0.33 μmol/kg, it being 30 times more potent than apomorphine and DiPr-6,7-ADTN. The results corroborate reported behavioural data, and the relative potencies of the alkylated derivatives in this test system for dopaminergic activity are in agreement with those based on stereotyped behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499913
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of non-catecholic 2-aminotetralin derivatives on dopamine metabolism in the rat striatum (1980)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 313 (1980), S. 213-219 
    Details
    ISSN: 1432-1912
    Keywords: 2-Aminotetralins ; Dopamine agonists ; Dopamine metabolism ; Striatum ; Structure activity relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The concentrations of dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were measured in the striatum of rats after i.p. injection of dipropyl-2-aminotetralin and the four positional isomers of monohydroxy-dipropyl-2-aminotetralin. All compounds except 8-OH dipropylaminotetralin caused a decrease in DOPAC-and HVA-concentrations. In addition, 5-OH-dipropylaminotetralin produced a small elevation in DA concentrations. In contrast, 7-OH dipropylaminotetralin, in doses of 100 μmol/kg and more, decreased DA to 50% and initially increased HVA and DOPAC to about 200%, after which the concentrations of the metabolites fell to 30% or less. The 5-OH isomer was found to be the most potent compound, decreasing HVA concentrations to 70% at a dose of 0.14 μmol/kg. The potencies are compared to those of catechol-group containing DA-agonists such as apomorphine and N,N-dipropyl-5,6-dihydroxy-2-aminotetralin. In addition, a comparison is made with reported behavioural data. It is suggested that the more active N-alkylated 2-aminotetralins have a conformation which corresponds to that of the α rotamer of dopamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00505736
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of the potencies of various dopamine receptor agonists in models for pre- and postsynaptic receptor activity (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 108-115 
    Details
    ISSN: 1432-1912
    Keywords: Dopamine agonists ; 2-Aminotetralins ; γ-Butyrolactone ; Presynaptic dopamine receptors ; Homovanillic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Several dopamine (DA) receptor agonists, notably N,N-dipropyl-2-aminotetralin analogues differing in the number and position of phenolic hydroxyl groups, were evaluated in model systems for pre- and postsynaptic dopaminergic activity. Apomorphine, piribedil and pergolide were included for comparison. All compounds inhibited the γ-butyrolactone (GBL)-induced increase in DA concentrations in the rat striatum and olfactory tubercle, although a dosedependency could not be demonstrated for one of the compounds, i.e. N,N-dipropyl-2-amino-5,6-dihydroxytetralin. In addition to the reversal of the DA-increase all compounds decreased the HVA and DOPAC levels in a dose-dependent manner, in much the same way as in normal, non GBL-pretreated rats. The potencies of the drugs to decrease HVA in normal rats and to inhibit the DA-increase and to decrease HVA in GBL-pretreated rats, both in the striatum and the olfactory tubercle were compared with each other and with the potencies to induce stereotyped behaviour. It may be concluded that (1) N,N-dipropyl-2-amino-7-hydroxytetralin shows the largest difference in activity in the biochemical and the behavioural models, suggesting a selective presynaptic activity. This was corroborated by the appearance of a marked hypomotility after low doses of this compound; (2) The potencies to decrease striatal HVA concentrations are generally somewhat different from the potencies to inhibit GBL-induced DA-increases, but appear to be comparable to the potencies to inhibit GBL-induced dihydroxyphenylalanine (DOPA)-increases; (3) There is no indication that the DA agonists in general are more potent at presynaptic receptors in the tubercle than in the striatum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00497015
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