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  • 1
    Electronic Resource
    Electronic Resource
    GABAB Receptor-Mediated Enhancement of Vasoactive Intestinal Peptide-Stimulated Cyclic AMP Production in Slices of Rat Cerebral Cortex (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 46 (1986), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Basal and vasoactive intestinal peptide (VIP)-stimulated accumulations of cyclic AMP were measured in slices of rat cerebral cortex. Neither γ-aminobutyric acid (GABA) nor the selective GABAB receptor agonist (–)-baclofen stimulated basal cyclic AMP accumulation, whereas VIP caused a large dose-dependent increase in cyclic AMP levels. However, in the presence of 100 μM (–)-baclofen, the effects of VIP on cyclic AMP accumulation were significantly enhanced, with the responses to 1 μM and 10 μM VIP being approximately doubled. The enhancing effects of (–)-baclofen was dose related (1–1,000 μM), but an enhancing effect was not observed with 100 μM (+)-baclofen. In the presence of the GABA uptake inhibitor nipecotic acid (1 mM), GABA caused a similar dose-related enhancement of the VIP response. The ability of either GABA or (–)-baclofen to augment VIP-stimulated production of cyclic AMP was not mimicked by the GABAA agonists isoguvacine and 4,5,6,7- tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP) and was not antagonized by the GABAA antagonist bicuculline. The putative GABAB antagonist 5-aminovaleric acid (1 mM) significantly reduced the effect of (–)-baclofen. The ability of (–)-baclofen to enhance VIP-stimulated accumulation of cyclic AMP was observed in slices of rat cerebral cortex, hippocampus, and hypothalamus. These results indicate that GABA and (–)-baclofen can enhance VIP-stimulated accumulation of cyclic AMP in rat brain slices via an interaction with specific GABAB receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1986.tb08493.x
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  • 2
    Electronic Resource
    Electronic Resource
    Aporphines. 48. Enantioselectivity of (R)-(-)- and (S)-(+)-N-n-propylnorapomorphine on dopamine receptors (1983)
    s.l. : American Chemical Society
    Journal of medicinal chemistry 26 (1983), S. 516-521 
    Details
    ISSN: 1520-4804
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jm00358a011
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  • 3
    Electronic Resource
    Electronic Resource
    Dopaminergic Mechanisms in the Teleost Retina (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A specific dopamine-sensitive adenylate cyclase has been identified in homogenates of the teleost (carp) retina. Maximal stimulation by 100 μM-dopamine resulted in a 5-10-fold increase in adenylate cyclase activity with half-maximal stimulation occurring at a concentration of 1 μM. l-Noradrenaline and l-adrenaline were some 10 times less potent than dopamine whilst the α-and β-adrenoreceptor agonists, l-phenylephrine and dl-isoprenaline were inactive. Apomorphine elicited a partial stimulation of adenylate cyclase activity whilst various ergot alkaloids produced mixed agonist/antagonist responses. Dopamine-stimulated adenylate cyclase activity was potently antagonised by various neuroleptic drugs including fluphenazine, α-flupenthixol and α-piflutixol, and to a lesser extent by the butyrophenone derivatives haloperidol and spiperone. The benzamide derivatives, metoclopramide and sulpiride. together with the α- and β-adrenoreceptor blocking agents, phentolamine and propranolol respectively, were essentially inactive at blocking dopamine-stimulated adenylate cyclase activity. These data suggest the presence of a highly specific dopamine-sensitive adenylate cyclase in homogenates of teleost retina possessing similar pharmacological properties to the dopamine-sensitive adenylate cyclase observed in the mammalian central nervous system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb01628.x
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  • 4
    Electronic Resource
    Electronic Resource
    Dopaminergic Mechanisms in the Teleost Retina (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 36 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The ability of dopamine, dopamine agonists, other proposed retinal neurotransmitters, depolarizing agents and light to stimulate adenylate cyclase activity in pieces of intact carp retina has been examined. The evidence indicates that a dopamine-sensitive adenylate cyclase is the only neurotransmitter activated adenylate cyclase in the carp retina. That is, only dopamine, or agents that activate dopamine receptors, appear to stimulate cyclic AMP synthesis in the retina. Depolarizing agents such as K+ or veratridine also increase retinal cyclic AMP levels, but apparently by releasing endogenous stores of dopamine. For example, the increase of retinal cyclic AMP levels induced by 45 mM-K+ is blocked by 5 mM-Co2+ or 100 μM-haloperidol, a dopamine antagonist. Flashing lights slightly increase cyclic AMP levels in the retina, an effect that is likewise abolished by haloperidol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb01629.x
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  • 5
    Electronic Resource
    Electronic Resource
    Comparison of the Binding of [3H]Spiperone and [3H]Domperidone in Homogenates of Mammalian Retina and Caudate Nucleus (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 37 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— The specific binding of [3H]spiperone and [3H]domperidone, as defined by 1 μm-(+)butaclamol, was compared in homogenates of bovine retina and caudate nucleus. Scatchard analyses of saturation data for [3H]spiperone binding yielded dissociation constants (Kd) of 0.35 nm in the retina and 0.64 nm in the caudate nucleus. Comparison of the maximum number of binding sites (Bmax) present in each tissue indicated that the density of sites in bovine caudate nucleus (270 fmol/mg protein) was approximately three times higher than in bovine retina (92 fmol/mg protein). This difference was even more marked in guinea pig tissues, with a ratio of 7:1 between corpus striatum and retina. The pharmacological analysis of [3H]spiperone binding in both the bovine retina and caudate nucleus indicated an interaction with dopaminergic rather than serotonergic sites. However, inhibition curves obtained to dopaminergic agonists in the bovine retina were significantly steeper than those observed in the bovine caudate nucleus, as reflected in the greater Hill coefficients obtained for these agents in the retina. Furthermore, only a small amount of specific [3H]domperidone binding was observed in either the bovine caudate nucleus or the guinea pig striatum, whilst no specific [3H]domperidone binding was detectable in homogenates of either bovine or guinea pig retina. These data suggest that the retina possesses only a small population of dopaminergic D2 sites and that these binding sites may differ from those present in the caudate nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb04663.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of Vasoactive Intestinal Peptide and Other Peptides on Cyclic AMP Accumulation in Intact Pieces and Isolated Horizontal Cells of the Teleost Retina (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 41 (1983), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The effects of vasoactive intestinal peptide (VIP) and several other peptides have been examined on cyclic AMP accumulation in intact pieces and isolated horizontal cells of the teleost (carp) retina. VIP was the most effective peptide examined, inducing a dose-related response, and an approximately fivefold increase in cyclic AMP production when used at a concentration of 10 μM. Porcine histidine isoleucine-containing peptide and secretin, peptides structurally related to VIP, also stimulated cyclic AMP accumulation, but at concentrations of 10 μM induced responses which were only approximately 40% and 10%, respectively, of the response observed with 10 μM VIP. In contrast, several other peptides, including glucagon, neurotensin, somatostatin, luteinizing hormone-releasing hormone, α-melanocyte-stimulating hormone, cholecystokinin octapeptide26–33, gastrin-releasing peptide, thyrotropin-releasing hormone, and VIP10–28 were totally inactive. The response to 10 μM VIP was not antagonized by several dopamine antagonists, indicating the presence of a population of specific VIP receptors coupled to adenylate cyclase, distinct from the population of dopamine receptors coupled to adenylate cyclase also known to be present in this tissue. Finally, experiments involving the use of fractions of isolated horizontal cells indicate that these neurons possess a population of VIP receptors coupled to cyclic AMP production which would appear to share a common pool of adenylate cyclase with a population of similarly coupled dopamine receptors. These data are discussed in terms of the presence, localization, and possible function of a putative VIP-ergic innervation in the carp retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1983.tb00813.x
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  • 7
    Electronic Resource
    Electronic Resource
    Interaction of the component enantiomers of the putative dopamine autoreceptor agonist, TL-99 (6,7-dihydroxy-2-dimethylamino tetralin) with dopaminergic systems in mammalian brain and teleost retina (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 324 (1983), S. 275-280 
    Details
    ISSN: 1432-1912
    Keywords: Dopamine autoreceptor ; Dopamine receptors ; TL-99
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The enantiomers of the putative dopamine auto-receptor agonist, TL-99 (6,7-dihydroxy-2-dimethylaminotetralin) were examined in a number of in vivo and in vitro test paradigms to further examine the reported autoreceptor selectivity of this compound. The (+)-isomer of the aminotetralin was more active as a dopamine agonist than either the racemate or the (−)-enantiomer. In addition to this dopaminergic activity, TL-99 was found to be a potent α2-adrenoceptor agonist, this activity being more prominent in the (+)-isomer. The (−)-isomer, however, was a weak α2/DA receptor agonist and unlike the (+)-enantiomer was devoid of activity in the D-1-selective carp retina adenylate cyclase assay. Pharmacological examination of the effects of TL-99 on mouse locomotor activity showed that the effects of the aminotetralin in this dopamine autoreceptor test system were antagonized by either the α2-antagonist, yohimbine or by the dopamine antagonist, sulpiride. TL-99 also produced contralateral turning in 6-OHDA lesioned rats. It is concluded that the apparent dopamine autoreceptor selectivity of TL-99 as assessed by in vivo animal test systems may be due partially to its α2-agonist activity. The sedation and consequent reduction in mouse locomotor activity and in turning in the rat as the dose level is increased undoubtedly occurs via α2-agonist and dopamine autoreceptor acitivity and cannot be interpreted as selectivity for the dopamine autoreceptor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00502623
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  • 8
    Electronic Resource
    Electronic Resource
    Dopamine receptors in the retina may all be linked to adenylate cyclase (1979)
    [s.l.] : Nature Publishing Group
    Nature 281 (1979), S. 578-580 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The dopamine-sensitive adenylate cyclase in the retina seems to be identical to that found elsewhere in the brain. Figure 1 shows, for example, adenylate cyclase activity in homogenates of the retina and corpus striatum of the guinea pig prepared in similar conditions. In both homogenates, dopamine ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/281578a0
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