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  • 1
    Electronic Resource
    Electronic Resource
    DECREASE OF HOMOVANILLIC, DIHYDROXYPHENYLACETIC ACID AND CYCLIC-ADENOSINE-3′,5′-MONOPHOSPHATE CONTENT IN THE RAT CAUDATE NUCLEUS INDUCED BY THE ACUTE ADMINISTRATION OF AN AMINOACID MIXTURE LACKING TYROSINE AND PHENYLALANINE (1976)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 26 (1976), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The oral administration of an aminoacid mixture lacking tyrosine and phenylalanine induces, in rats, a profound depletion of tyrosine in serum and in brain. Brain tyrosine is maximally depleted by 73%, 2 h after treatment, when there is a concomitant decrease in the levels of HVA (by 50%), DOPAC (by 30%) and c-AMP (by 28%) in the basal ganglia. However, 4 to 8 h after treatment, when brain tyrosine is still depleted by 47 and 28%, respectively, DA metabolites and c-AMP levels have returned to normal. Our findings indicate that striatal tyrosine hydroxylase is fully saturated in v i m by the concentrations of tyrosine normally present in the basal ganglia. The results also suggest indirectly that decreased DA turnover results in decreased nerve activity, as judged by the decreased cyclic AMP levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1976.tb07014.x
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  • 2
    Electronic Resource
    Electronic Resource
    INHIBITION BY APOMORPHINE OF DOPAMINE DEAMINATION IN THE RAT BRAIN (1974)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 23 (1974), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Apomorphine (A) inhibited dopamine deamination by rat brain mitochondria, but did not influence catechol-O-methyltransferase (COMT) activity by brain homogenates. The administration of apomorphine (10mg/kg i.p.) to normal rats increased brain dopamine (DA) by 34 per cent and decreased homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC) by 60 per cent. In rats treated with reserpine 15 min prior to A, the latter prevented the rise of cerebral HVA and DOPAC and the depletion of DA produced by the former. Finally, A decreased the L-DOPA-induced accumulation of HVA and DOPAC in the rat basal ganglia. These results indicate that A inhibits DA deamination by monoamine oxidase.This inhibition seems to be specific since apomorphine did not influence 5-HIAA levels in normal rats and prevented neither central 5-HT depletion nor 5-HIAA rise induced by reserpine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1974.tb12205.x
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  • 3
    Electronic Resource
    Electronic Resource
    Involvement of D1 and D2 Dopamine Receptors in the Control of Horizontal Cell Electrical Coupling in the Turtle Retina (1989)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 1 (1989), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We studied the actions of D1 and D2 dopamine agonists and antagonists on the coupling of horizontal cell axons in the turtle retina by a combinationn of pharmacological and electrophysiological methods. Both D1 and D2 receptors were identified in membrane fractions by radioligand binding using [3H]-SCH 23390 and [3H]-spiperone, respectively. The KD of both receptor classes were identical (0.21 nM) but D1 receptor density exceeded that of D2 receptors by more than four-fold. D1 agonists increased the activity of adenylate cyclase in a dose-dependent manner, whereas D2 agonists were without significant effect by themselves, nor did D2 antagonists block the D1-mediated increase in adenylate cyclase activity. Intracellular recordings and Lucifer Yellow dye injections were used to characterize the modifications of the receptive field profile of horizontal cell axons (H1AT) exposed to different pharmacological agents. Dopamine or D1 agonists (0.05–10 μM) induced a marked constriction of the H1AT receptive field, whereas D2 agonists elicited a small expansion of the receptive field. However, in the presence of a D1 antagonist, as well as IBMX to inhibit phosphodiesterase, D2 agonists (10–70 μM) induced a marked increase in the receptive field profile. These results indicate that both D1 and D2 dopamine receptors play a role in shaping the receptive field profile of the horizontal cell axon terminal in the turtle retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1989.tb00792.x
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  • 4
    Electronic Resource
    Electronic Resource
    Postsynaptic receptors are not essential for dopaminergic feedback regulation (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 270-272 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Male oprague-Dawley rats (290-310 g) were anaesthetised with Equithesin and placed on a stereotaxic frame (Kopf); kainic acid (Sigma) dissolved in 1 v\ of saline was injected in 2 min in the caudate of one side while that of the other side received the same volume of saline. Coordinates were A 2.2, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/267270a0
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for dopamine receptors mediating sedation in the mouse brain (1976)
    [s.l.] : Nature Publishing Group
    Nature 264 (1976), S. 564-567 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] While the stimulant effect is considered to be due to the activation of postsynaptic DA receptors in brain4,3, it has been suggested that the depressant response to these drugs is due to the activation of DA "autoreceptors", which would result in inhibition of DA synthesis and dopaminergic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/264564a0
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in gastro-intestinal serotonin content associated with fasting and satiation (1977)
    Springer
    Cellular and molecular life sciences 33 (1977), S. 745-746 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rats fasted for 24 h were fed for 3 h, after whith time food was removed. Food intake decreased serotonin levels in the stomach and duodenum by 30 and 40%, respectively. These changes persisted for about 3 h. Food intake did not change tryptophan content in the stomach, while, in the duodenum, tryptophan level rose by 100% at the end of the feeding period and remained elevated for about 9 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01944166
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancement by flumazenil of dopamine release in the nucleus accumbens of rats repeatedly exposed to diazepam or imidazenil (1997)
    Springer
    Psychopharmacology 131 (1997), S. 34-39 
    Details
    ISSN: 1432-2072
    Keywords: Key words Benzodiazepine receptor partial agonist ; Long-term treatment ; Withdrawal syndrome ; Dopamine release ; Nucleus accumbens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of long-term treatment (three times daily for 3 weeks) with a behaviorally relevant dose of the benzodiazepine receptor partial agonist imidazenil (0.5 mg/kg, IP) on basal dopamine release in the nucleus accumbens of freely moving rats was compared with that of diazepam (3 mg/kg, IP), a benzodiazepine receptor full agonist. Challenge doses of imidazenil and diazepam decreased the extracellular dopamine concentration in the nucleus accumbens by approximately the same extent in animals repeatedly exposed to vehicle or to the respective drug. Moreover, the abrupt discontinuation of long-term treatment with diazepam or imidazenil failed to affect basal dopamine release in this brain area during the first 5 days of withdrawal. In contrast, administration of the benzodiazepine receptor antagonist flumazenil (4 mg/kg, IP) elicited a marked increase (95 or 60%) in dopamine release in the nucleus accumbens 6h after withdrawal of diazepam or imidazenil, respectively. Flumazenil induced a similar but smaller effect (50% increase) 5 days after diazepam withdrawal but had no effect 5 days after discontinuation of imidazenil treatment. The resultssupport an involvement of the mesoaccumbens dopaminergic neurons in the withdrawal syndrome precipitated by flumazenil and allow further differentiation of benzodiazepine receptor partial and full agonists with respect to dependence liability of dopaminergic neurons in the nucleus accumbens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002130050262
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  • 8
    Electronic Resource
    Electronic Resource
    Evidence for selective and long-lasting stimulation of “regulatory” dopamine-receptors by bromocriptine (CB 154) (1977)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 300 (1977), S. 239-245 
    Details
    ISSN: 1432-1912
    Keywords: Bromocriptine ; CB 154 ; Dopamine metabolism ; Motility ; Sedation ; Dopamine receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Bromocriptine, an ergot-derivate with DA-receptor stimulating properties in vivo, produces long-lasting hypomotility in mice not accustomed to the motility cage and decreases brain DOPAC and HVA without affecting brain DA. These effects are obtained with doses 25 times lower than those which produce hypermotility. The decrease of brain DOPAC is correlated to the hypomotility both on a dose- and on a time-basis. Potent neuroleptics as pimozide, benzperidol and droperidol, which are considered to be fairly specific DA-receptor blockers, antagonize the hypomotility and the decrease of brain DOPAC produced by bromocriptine. These effects are obtained with very low doses (0.05–0.3 mg/kg) of neuroleptics which per se do not affect motility or brain DOPAC. The maximal decrease of brain DOPAC and HVA produced by bromocriptine is similar to that produced by apomorphine and the combination of these drugs does not result in a further decrease of brain DOPAC or HVA. On the basis of these results it is postulated that bromocriptine decreases brain DA-turnover and produces hypomotility by acting on “regulatory” DA-receptors different from the post-synaptic ones of the “terminal” dopaminergic areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500966
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  • 9
    Electronic Resource
    Electronic Resource
    Substantia nigra as an out-put station for striatal dopaminergic responses: Role of a GABA-mediated inhibition of pars reticulata neurons (1979)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 306 (1979), S. 153-159 
    Details
    ISSN: 1432-1912
    Keywords: Substantia nigra ; GABA ; Turning ; Picrotoxin ; Bicuculline ; Kainic acid ; Striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intranigral administration of kainic acid results in loss of pars reticulata neurons without damage to axons traversing or terminating within the nigra. Unilateral nigral lesions with kainic acid result in an ipsilateral turning upon administration of apomorphine, a dopamine (DA)-receptor agonist and in contralateral turning upon administration of haloperidol, a DA-receptor blocker. Destruction of post-synaptic structures in the striatum of the side contralateral to that injected with kainic acid results in a drastic reduction, abolition or even reversal of the turning effects elicited by apomorphine and haloperidol. Unilateral intranigral microinjection of nanogram amounts of the GABA-receptor antagonists picrotoxin and bicuculline elicits ipsilateral circling upon apomorphine administration. Kainic-induced lesion or micro-injection of picrotoxin or bicuculline in the nigra ipsilateral to a 6-OHDA-lesion of nigro-striatal DA-neurons results in reduction, abolition or reversal of the contralateral circling produced by apomorphine. The results indicate that the nigra pars reticulata is a station for dopaminergic impulses originating from the striatum and suggest that the turning behavior in response to striatal DA-receptor stimulation is due to a GABA-mediated inhibition of ipsiversive pars reticulata neurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00498985
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  • 10
    Electronic Resource
    Electronic Resource
    Differential effect of aging on3H-SCH 23390 binding sites in the retina and in distinct areas of the rat brain (1990)
    Springer
    Journal of neural transmission 82 (1990), S. 157-166 
    Details
    ISSN: 1435-1463
    Keywords: D-1 dopamine receptors ; aging ; 3H-SCH 23390 ; striatum ; substantia nigra ; olfactory tubercle ; retina ; dopamine metabolism ; DOPAC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of age on the binding parameters of the selective D-1 dopamine (DA) receptor antagonist3H-SCH 23390 were studied in membrane preparations from rat striatum, substantia nigra, olfactory tubercle, prefrontal cortex and retina. When compared with 3-month-old animals, there was a significant decrease in the density of3H-SCH 23390 binding sites in the striatum (−25%), substantia nigra (−24%), and olfactory tubercle (−23%), but not in the prefrontal cortex of senescent (23-month-old) rats. The affinity of3H-SCH 23390 for D-1 DA receptors did not change with age in any of the brain areas analyzed. In contrast, the density of3H-SCH 23390 binding sites was higher (+53%) in the retina of aged rats that in 3-month-old controls. Confirming previous studies, we observed that light deprivation induced a significant increment in the density of3H-SCH 23390 binding sites in the retina of adult rats (+31%) but not in the retina of aged animals. The ability of light exposure to activate DAergic neurons in the rat retina was not altered by normal aging. In fact, a similar increase in the concentration of DOPAC was observed in the retina of light-adapted adult and senescent rats when compared to their respective dark-adapted controls (+94% and +95%, respectively). The results indicate that aging has a differential effect on D-1 DA receptors in the retina and different areas of the rat brain. Finally, the age-related increment in the density of retinal D-1 DA receptors does not appear to depend on presynaptic mechanisms, since DA metabolism is increased by light to the same extent in young and aged rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01272759
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