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J Glowinski

Publications and source records attributed to J Glowinski.

At least 469 records · Page 26Linked to original sources
PubMed1976

Topographical distribution of dopaminergic innervation and of dopaminergic receptors in the rat striatum. I. Mictoestimation of [3H] dopamine uptake and dopamine content in microdiscs.

Topographical variations in the uptake of [3H] dopamine (DA) and in the endogenous content of DA were estimated in the striatum of the rat. For this purpose, microdiscs were punched out in serial 500 mum sections. [3H] DA uptake was measured in 0.25 M sucrose homogenates prepared from microdiscs punched out from frozen slices (--7C). This uptake was similar to that observed in fresh tissues. It was unaffected by desmethylimipramine (5 X 10(-7) M), inhibited by benztropine (10(-6) M) and no longer detectable after 6-hydroxydopamine-induced degeneration of the nigrostriatal dopaminergic pathway. Both [3H] DA uptake and DA content decreased regularly from the rostral to the caudal part of the structure. In contrast, no important differences could be found in the dorso-ventral plane. These results suggest that the extent of dopaminergic innervation is heterogenous within the structure.

Animals↗
PubMed1976

Topographical distribution of dopaminergic innervation and of dopaminergic receptors in the rat striatum. II. Distribution and characteristics of dopamine adenylate cyclase--interaction of d-LSD with dopaminergic receptors.

The characteristics of dopamine adenylate cyclase in the rat striatum were first studied on homogenates of fresh tissues. In the assay conditions used, dopamine (10(-4) M) stimulated the enzyme activity by 250%. This effect was completely blocked by fluphenazine (10(-5) M; Ki=9X10(-9) M) and by phentolamine (10(-5) M; Ki=3 X 10(-7) M). D-LSD stimulated the adenylate cyclase activity (Km=1.4 X 10(-7) M) by interacting with dopamine receptors; indeed the dopamine effect on the enzyme activity was competitively reduced in presence of D-LSD. L-Isoproterenol (Km=10(-6) M) activated an adenylate cyclase through a receptor distinct form the dopaminergic receptor; this stimulation was not affected by fluphenazine or phentolamine but suppressed by DL-propranolol (10(-4) M). The topographical distribution of the dopamine, D-LSD and L-isoproterenol adenylate cyclase activities were examined in homogenates prepared from discs punched out on serial frozed (--7C) slices of the striatum. Under this condition, tge dioanube naxunak stunykatuib was if 150%. A 4.8-fold progressive decrease in the amount of cyclic AMP produced in presence of dopamine (10(-4) M) was observed in the rostrocaudal plane of the structure; the decline of the basal activity was 3.6-fold. The topographical curves of maximal activation of adenylate cyclase by dopamine and D-LSD were superimposable confirming that D-LSD acts on dopaminergic receptors. This topographical distribution of dopamine sensitive adenylate cyclase is comparable on one hand to that of endogenous dopamine and on the other hand to that of the dopamine high affinity uptake activity measured in simultaneous experiments. In contrast to that observed with dopamine or D-LSD, the topographical distribution of the adenylate cyclase sensitive to L-isoproterenol was homogenous within the striatum.

Adenylyl Cyclases↗
PubMed1976

Nicotinic effect of acetylcholine on the release of newly synthesized (3H)dopamine in rat striatal slices and cat caudate nucleus.

The effect of acetylcholine (ACh), carbachol and nicotinic blocking agents on the release of newly synthesized [3H]dopamine ([3H]DA) was studied in vitro on rat striatal slices and in vivo on the cat caudate nucleus. In the latter case, the animals were anaesthetized with halothane; in some experimetns an 'encéphale isolé' preparation was used to eliminate anaesthesia. Rat striatal slices placed in a superfusion chamber were continuously superfused with L-[3,5-3H]tyrosine. A cup placed on the ventricular surface of the cat caudate nucleus similarly allowed a continuous superfusion of the structure with the 3H amino acid. In both cases the quantities of [3H]DA contained in serial superfusate fractions were estimated; the drugs were always added in superfusing medium. In vitro ACh (10(-5) M) and carbachol (10(-5) M) enhanced the release of [3H]DA (90%). Similar results were obtained in vivo in anaesthetized cats. The effect of ACh (10(-5) M) was more pronounced (125%) in presence of eserine (10(-4) M) than with ACh alone (65%). ACh was also effective in unanaesthetized cats. The ACh effect on [3H]DA release was reproducible within the same experiment both in vitro and in vivo. This allowed to test the effect of anticholinergic agents on the ACh induced release of [3H]DA. In vivo hexamethonium (10(-4) M, 10(-5) M) partially blocked the release of [3H]DA induced by ACh (10(-5) M) alone; the effect was not seen when ACh was added in the presence of eserine (10(-4) M). Both in vivo and in vitro the prior introduction of mecamylamine into the superfusing medium antagonized the stimulating effect of ACh (10(-5) M) on [3H]DA release. The effects of this nicotinic blocking agent were seen with various concentrations (10(-6); (10(-5) 10(-4) in the in vitro experiments.

Acetylcholine↗
PubMed1976

In vivo release of 5-HT in the lateral ventricle of the rat: effects of 5-hydroxytryptophan and tryptophan.

The in vivo release of 5-HT was examined in the rat brain. For this purpose, the left lateral ventricle was perfused at a constant rate with an artificial CSF for several hours in animals anaesthetized with halothane. 5-HT was estimated in serial 1-h collected fractions. The amine was first isolated by adsorption on a Sephadex G-10 column and then assayed using the radioenzymatic method of Saavedra et al.37, slightly modified to improve its sensitivity. The quantity of 5-HT released spontaneously during the first hour fraction was 296 pg, it was lower (99 pg/h) in the following fractions. 5-HT released into the CSF may in great part originate from serotoninergic terminals localized in structures surrounding the ventricle. This was suggested by experiments in which exogenous [3H]5-HT or [3H]tryptophan were perfused through the lateral ventricle during a few hours. [3H]5-HT taken up or synthetized was mainly localized in structures surrounding the ventricular space. The acute injection of 5-hydroxytryptophan (100 mg/kg) induced an immediate important and long lasting increase of 5-HT release. In contrast the acute injection of tryptophan (100 mg/kg) led to a transient and moderate elevation of 5-HT release which was only detected during the second hour of perfusion. Curiously a similar pattern of transmitter release was observed following the constant intravenous infusion of the amino acid (70 mg/kg/h) except that the increase in 5-HT release was much more pronounced during the second hour than after the acute injection. Parallel experiments were made to determine the time course of the changes of free and total tryptophan levels in plasma and of those of tryptophan, 5-HT, and 5-hydroxyindoleacetic-acid (5-HIAA) in brain tissues, induced by the acute and long term administrations of tryptophan. Moreover the rate of 5-HT synthesis was estimated using the monoamine oxidase inhibition method 2 and 5 h after both tryptophan treatments in halothane anaesthetized rats. 5-HT levels and the synthesis rate of the transmitter were increased at 2 h (when both tryptophan treatments stimulated 5-HT release). Despite the presence of high tryptophan levels in plasma and tissues and of high 5-HT and 5-HIAA levels in tissues, the synthesis rate of 5-HT (as the 5-HT release) was similar to that of controls 5 h after the onset of tryptophan infusion. These results suggest that some relationships occurred between the changes in 5-HT SYNTHESIs and release after the first hour of perfusion. The absence of effects of tryptophan treatments on 5-HT release during the first hour of perfusion are also discussed.

5-Hydroxytryptophan↗
PubMed1976

The role of presynaptic receptors in the release and synthesis of 3H-dopamine by slices of rat striatum.

Striatal slices were continuously superfused with L-3,5-(3)H-tyrosine (50 muCi/ml) and 4H-H2O [index of 3H-dopamine (3H-DA) synthesis] and 3H-DA estimated in 0.5 ml (2.5 min) superfusate fractions. Depolarization with 50 mM K+ for 7.5 min induced a marked increase in 3H-DA release and a biphasic effect on synthesis (slight increase in the first fraction followed by a significant decrease in the third and fourth fractions). The decrease in the rate of 4H-H2O formation induced by K+ was not related to modifications of the specific activity of tyrosine in tissues. The possibility that the inhibition of synthesis was due to alterations in DA concentration in the synaptic cleft was examined. Benztropine in a concentration which produced inhibition of DA uptake (10(-6) M) increased the K+ induced overflow of 3H-DA but failed to alter the inhibition of synthesis. On the other hand, when the powerful neuroleptic fluphenazine was added to the superfusion medium in a concentration which only weakly blocked 3H-DA uptake (10(-6) M) it potentiated 3H-DA release and prevented the inhibition of synthesis both in the absence or presence of benztropine. A similar effect was seen following the in vivo treatment of rats with fluphenazine (2 mg/kg; 1 1/2 h before sacrifice). The addition of exogenous DA (0.6 X 10(-6) M) or NA (10(-6) M) to the superfusion medium increased 3H-DA outflow and reduced DA synthesis while isoproterenol (10(-6) M) was without effect. The DA inhibitory effect on synthesis was still observed in the presence of benztropine (10(-6) M) while the NA effect was prevented. This concentration of benztropine blocked both DA and NA uptake. The administration of fluphenazine (10(-6) M) significantly prevented the decrease in 3H-DA synthesis induced by exogenous DA and partially prevented the effect of NA. In addition, the effect of exogenous DA on the inhibition of synthesis was still seen in the presence of 2-amino-4-hydroxy-6,7-dimethyl-5,6,-7,8-tetrahydropteridine hydrochloride (DMPH4) (to protect against end-product inhibition). The present results provide direct support for the concept that activation of presynaptic DA receptors located on DA terminals in the striatum of the rat results in an inhibition of synthesis and release of the transmitter.

Animals↗
PubMed1976

The effects of quipazine on 5-HT metabolism in the rat brain.

Since quipazine is a potent 5-HT agonist in peripheral organs, its possible stimulatory effects on serotoninergic receptors in the rat brain were investigated. Quipazine administration (10 mg/kg, i.p.) induced a significant decrease in the synthesis and turnover rates of serotonin in the brain stem as well as in the forebrain. It is not likely that these changes were mediated by a negative feed-back mechanism triggered by a direct action of quipazine on central 5-HT postsynaptic receptors. Indeed, in contrast to LSD and 5-methoxy-N,N-dimethyltryptamine, this compound failed to activate the 5-HT sensitive adenylate cyclase in colliculi homogenates of newborn rats. However, quipazine exerted direct effects on serotoninergic terminals. It inhibited competitively the reuptake process in synaptosomes (Ki=1.38 X 10(-7) M) and stimulated the K+ evoked release of newly synthesized 3H-5-HT in slices of the brain stem. Injected in vivo in a dose which affected 5-HT uptake and release, quipazine did not modify MAO activity. However, this activity was non-competitively inhibited by high concentratin of the drug in vitro (Ki=3.0 X 10(-5) M). These actions are very likely indirectly responsible for the stimulation of central 5-HT receptors.

Adenylyl Cyclases↗
PubMed1975

Effects of dopaminergic receptor agonists and antagonists on the activity of the neo-striatal cholinergic system.

The effects of various neuroleptics and of apomorphine on the metabolism of ACh were examined in the neostriatum of the rat. For this purpose, a specific radio-enzymatic assay for brain ACh was used. This method is based on the preliminary purification of the choline esters by liquid cation exchange, separation of choline and ACh on thin layer chromatography plates, hydrolysis of ACh then reactylation of the choline moiety with a purified and stabilized rat brain choline acetyltransferase. The rat neostriatal ACh levels were decreased by neuroleptics of the phenothiazine and butyrophenone type and increased by apomorphine. An "in vivo" estimation of the rate of utilization of ACh was obtained by measuring the decline in neostriatal ACh content following the local microinjection of hemicholinium-3. This compound blocked almost totally the synthesis of ACh in these conditions. Chlorpromazine (15 mg/kg) enhanced neo-striatal ACh utilization and apomorphine (10 mg/kg) antagonized this effect. Neuroleptics did not effect ACh levels in the parietal cerebral cortex and the hippocampal formation. The modifications of the activity of neostriatal cholinergic neurons by chlorpromazine and apomorphine were still observed following the degeneration of the nigro-neostriatal dopaminergic fibers induced by the injection of 6-hydroxydopamine into the substantia nigra. The results strongly suggest that dopaminergic receptors as defined by their pharmacological interaction with neuroleptics and apomorphine are localized on neostriatal ACh neurons.

Acetylcholine↗