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  • 1
    Electronic Resource
    Electronic Resource
    The use of tetrodotoxin for the characterization of drug-enhanced dopamine release in conscious rats studied by brain dialysis (1987)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 336 (1987), S. 502-507 
    Details
    ISSN: 1432-1912
    Keywords: Brain dialysis ; Striatum ; Nucleus accumbens ; Dopamine ; Amphetamine ; Tetrodotoxin ; Morphine ; 1-methyl-4-phenylpyridinium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of TTX (infused during brain dialysis of the striatum and nucleus accumbens) on the in vivo release of dopamine, 3,4-dihydroxyphenylacetic acid and homovanillic acid, was investigated. In addition it was studied whether the increase in the release of dopamine, induced by various pharmacological treatments, was sensitive to TTX infusion. The following drugs were studied: haloperidol, amphetamine, haloperidol co-administered with GBR 12909, morphine and MPP+. Dialysis was carried out in the striatum, except for morphine, which was studied in the nucleus accumbens. The infusion of TTX revealed three different types of pharmacologically enhanced dopamine release in conscious rats. First, action potential dependent dopamine release (exocytosis), which was observed in untreated animals as well as in animals treated with haloperidol, haloperidol + GBR 12909, and morphine. Second, action potential independent release (carrier-mediated) was established in the case of amphetamine. Third, action potential independent DA release, probably caused by neurotoxic reactions was observed during MPP+ infusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169306
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  • 2
    Electronic Resource
    Electronic Resource
    The significance of extracellular calcium for the release of dopamine, acetylcholine and amino acids in conscious rats, evaluated by brain microdialysis (1988)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 337 (1988), S. 373-378 
    Details
    ISSN: 1432-1912
    Keywords: Brain dialysis ; Striatum ; Dopamine ; Acetylcholine ; Verapamil ; Calcium ; Magnesium ; Amino acids ; Haloperidol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of the calcium concentration of the perfusion fluid on the release of striatal dopamine recorded by brain dialysis was investigated. The release of dopamine appeared very sensitive to the calcium concentration of the Ringer. Next we studied whether three different methods known to antagonize the effects of calcium entry, were able to affect the release of dopamine. The conditions investigated were: the use of calcium-free Ringer, infusion of magnesium, and infusion of the calcium-antagonist verapamil. Calcium-antagonism was studied on the day of implantation of the cannula as well as on several days thereafter. It appeared that magnesium infusion was the most effective condition to antagonize the effects of calcium on the release of dopamine. Magnesium infusion was also most effective in preventing drug-evoked voltage-dependent dopamine release (induced by coadministration of haloperidol and GBR 12909). In addition magnesium infusion appeared a potent antagonist of acetylcholine release. In contrast, the dialysate content of aminoacids was not influenced by magnesium infusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169526
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  • 3
    Electronic Resource
    Electronic Resource
    Dopaminergic-cholinergic interactions in the striatum: the critical significance of calcium concentrations in brain microdialysis (1990)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 342 (1990), S. 528-534 
    Details
    ISSN: 1432-1912
    Keywords: Brain microdialysis ; Acetylcholine ; Dopamine ; Calcium ; Perfusion solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Brain microdialysis experiments were performed to assess the effects of calcium (1.2 mmol/l and 3.4 mmol/l) in the perfusio solution on a variety of pharmacological treatments known to affect the release of dopamine (DA) and/or acetylcholine (ACh). Intrastriatal infusion of the muscarinic receptor agonist oxotremorine (100 μM), the selective dopamine D-2 receptor agonist (−)-N-0437 (1 μM), and the indirect DA agonists (+)amphetamine (10 μM) and nomifensine (1 μM) via the dialysis probe did not affect the overflow of ACh when the perfusion fluid contained 3.4 mmol/l calcium. In contrast, these compounds produced pronounced decreases in the overflow of ACh at 1.2 mmol/l calcium. Intrastriatal infusion of the muscarinic receptor antagonist atropine (1 μM) increased the output of ACh both at 1.2 mmol/l and 3.4 mmol/1 calcium. The selective DA D-2 receptor antagonist (−)-sulpiride (1 μM) did not affect the overflow of ACh at either calcium concentration. Infusion of oxotremorine and atropine had no effect on the overflow of DA at either 1.2 mmol/l or 3.4 mmol/l calcium. (−)-N-0437 decreased and (−)-sulpirde increased DA overflow, both effects being independent of the calcium concentration in the perfusion fluid. Nomifensine and (−)amphetamine caused relatively (but not absolutely) larger increases in the overflow of DA at 1.2 mmol/1 calcium. These findings emphasize the critical importance of the calcium concentration of the perfusion fluid in determining the nature of pharmacological responses in microdialysis experiments, and demonstrate that locally applied dopaminergic drugs can modulate striatal cholinergic function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169041
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  • 4
    Electronic Resource
    Electronic Resource
    Dopaminergic regulation of striatal cholinergic interneurons: an in vivo microdialysis study (1990)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 342 (1990), S. 523-527 
    Details
    ISSN: 1432-1912
    Keywords: Acetylcholine ; Choline ; Dopaminergic agents ; Microdialysis ; Rat ; Striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In vivo microdialysis was used to study the putative inhibitory effects of dopamine on cholinergic interneurons in the striatum of conscious rats. The dopamine receptor agonists apomorphine (0.3 and 3 mg/kg, s.c.) and (±)N-0437 (1.4 mg/kg, s.c.) decreased interstitial concentrations of acetylcholine while increasing those of choline. In contrast, the dopamine receptor antagonists haloperidol (0.1 and 1 mg/kg, i.p.) and (±)sulpiride (20 mg/kg, i.p.) enhanced striatal acetylcholine output but had little effect on choline. Previously, a lack of effect of these drugs on striatal acetylcholine was reported. The main methodological difference between these studies was that the calcium concentration of the microdialysis perfusion solution was 3.4 mM in the former study versus 1.2 mM in the present experiments. The results of this study reemphasize the importance of the calcium concentration in determining the effects of drugs on central neurotransmitter release, and confirm a role of dopamine in the regulation of striatal cholinergic interneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169040
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of intrastriatal application of directly and indirectly acting dopamine agonists and antagonists on the in vivo release of acetylcholine measured by brain microdialysis (1992)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 345 (1992), S. 144-152 
    Details
    ISSN: 1432-1912
    Keywords: Acetylcholine release ; Dopamine release ; Microdialysis ; Striatum ; D-1 and D-2 dopamine receptors ; Post-implantation interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of intrastriatal application of D-1, D-2 and indirect dopaminergic drugs on the release of striatal acetylcholine as a function of the post-implantation intervals was studied using in vivo microdialysis. The dopamine, D-2 agonists LY 171555 and (−)N0437 inhibited the release of striatal acetylcholine to 40% of control values 16–24 h after implantation of the dialysis cannula. When LY 171555 was infused 40–48 h after implantation of the dialysis cannula, the response was attenuated to 20% of control values. Meanwhile, the effectiveness of infusions of the antagonists (−)sulpiride and haloperidol was augmented from a non significant effect at 16–24 h to a 150% increase 40–48 h after implantation of the cannula. Infusions of the dopamine releasing agent amphetamine or the dopamine uptake inhibitor nomifensine resulted in a dose-dependent increase in the overflow of dopamine. Not until a sevenfold increase in the level of dopamine was seen, the release of acetylcholine was significantly affected. This hyporesponsiveness of the striatal cholinergic interneurons to endogenous dopamine could not be attributed to dopamine D-1 receptor activation, since no effects on striatal acetylcholine release were found by intrastriatal infusions of the selective D-1 agonist CY 208-243 or the selective D-1 antagonist SCH 23390. The results indicate that dopamine D-2 receptors are involved in the regulation of striatal acetylcholine release and that these receptors are tonically occupied by endogenous dopamine under the present experimental conditions 40–48 h after probe implantation. The fact that cholinergic responses to intrastriatally applied dopaminergic agents are dynamic with respect to the time between implantation surgery of the dialysis tube and the experimental measurements suggests that the striatal neuronal system is perturbated by the implantation of a dialysis probe for a considerable length of time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165729
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