caa a22 4500 46907809X CHVBK 20180323132941.0 cr unu---uuuuu 170328e19921201xx s 000 0 eng 10.1007/BF00168742 doi (NATIONALLICENCE)springer-10.1007/BF00168742 Adenosine but not an adenine nucleotide mediates tonic purinergic inhibition, as well as inhibition by glutamate, of noradrenaline release in rabbit brain cortex slices [Elektronische Daten] [Ivar von Kügelgen, Leni Späth, Klaus Starke] Summary: A possible contribution of adenine nucleotides to the endogenous purinergic, A1-receptor-mediated inhibition of noradrenaline release was studied in rabbit occipito-parietal cortex slices. The slices were preincubated with [3H]-noradrenaline and then superfused and stimulated electrically, in most experiments by trains of 6 pulses/100 Hz. A few experiments were carried out in rat occipito-parietal cortex slices. The A1-purinoceptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 1-100 nmol/l) as well as the enzyme adenosine deaminase (0.1-10 U/ml) increased the electrically evoked overflow of tritiated compounds. The maximal increase was by about 85% for both DPCPX and adenosine deaminase. The increases obtained with maximally effective concentrations of DPCPX and adenosine deaminase were not additive. The α1-adrenoceptor-selective agonist methoxamine (10 but not 1 μmol/l) reduced the evoked overflow. Its effect was antagonized by yohimbine 1 μmol/l but then not attenuated further by DPCPX100 nmol/l.L-Glutamate (300 μmol/l-2.3 mmol/l) also reduced the evoked overflow of tritium. Its effect was not changed by yohimbine 1 μmol/l but greatly, and to the same extent, attenuated by DPCPX 100 μmol/l and adenosine deaminase 3 U/ml. Neither the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine nor omission of Mg++ changed the inhibition by glutamate. Glutamate did not alter the basal efflux of tritium from rabbit cortex slices under any experimental condition. In contrast, glutamate (100 μmol/l and 1 μmol/l) caused an immediate, marked and transient acceleration of tritium outflow from rat occipitoparietal cortex slices (medium without Mg++). It is concluded that adenosine but not an adenine nucleotide mediates the tonic purinergic presynaptic inhibition of noradrenaline release in rabbit brain cortex. The marked degree of disinhibition by DPCPX and adenosine deaminase underscores the potential physiological role of this inhibition. The purinergic inhibitory tone is reinforced by glutamate, indicating that glutamate releases adenyl compounds in rabbit brain cortex. Again adenosine but not an adenine nucleotide mediates the indirect inhibition by glutamate of the release of noradrenaline. The noradrenaline-releasing effect that glutamate exerts in rat occipito-parietal cortex does not occur in rabbit occipito-parietal cortex. Methoxamine depresses the release of noradrenaline in rabbit brain cortex directly at presynaptic α2-adrenoceptors rather than by release of purines. Springer-Verlag, 1992 Presynaptic adenosine A1-receptors nationallicence Adenine nucleotides nationallicence Glutamate nationallicence Noradrenaline release nationallicence Rabbit brain cortex nationallicence von Kügelgen Ivar Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut Späth Leni Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut Starke Klaus Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/6(1992-12-01), 677-684 0028-1298 346:6<677 1992 346 210 https://doi.org/10.1007/BF00168742 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00168742 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- von Kügelgen Ivar Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut NATIONALLICENCE 700 1- Späth Leni Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut NATIONALLICENCE 700 1- Starke Klaus Pharmakologisches Institut, Hermann-Herder-Strasse 5, W 7800, Freiburg i. Br., Federal Republic of Germany aut NATIONALLICENCE 773 0- Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/6(1992-12-01), 677-684 0028-1298 346:6<677 1992 346 210 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer