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R Quirion

Publications and source records attributed to R Quirion.

At least 361 records · Page 20Linked to original sources
PubMed1985

Possible interactions between dynorphin and dopaminergic systems in rat basal ganglia and substantia nigra.

Chronic haloperidol treatment markedly increases dynorphin-related peptide contents in caudate-putamen, globus pallidus and substantia nigra. Leu-enkephalin levels follow dynorphin-related peptide concentrations in these areas while Met-enkephalin-related peptide contents are unchanged in the substantia nigra following a similar treatment. An acute haloperidol injection had no effect on any opioid peptide levels in the basal ganglia. This suggests that Leu-enkephalin is likely to be derived from prodynorphin in the rat striatonigral pathway. Moreover, the Leu-enkephalin/dynorphin projection appears to be under striatal dopaminergic control.

Animals↗
PubMed1985

Imipramine treatment differentially affects platelet 3H-imipramine binding and serotonin uptake in depressed patients.

Uptake of serotonin and 3H-imipramine binding in platelets of depressed patients were investigated simultaneously with changes in clinical state. Both Vmax for serotonin uptake and Bmax for 3H-imipramine binding were significantly lower in unmedicated depressed patients with respect to normal subjects. Successful treatment with imipramine led to a significant increase in Bmax for 3H-imipramine binding, without significant change in Vmax for serotonin uptake. Bmax values increased to the normal range following complete, rather than partial clinical improvement. These data indicate that successful antidepressant treatment may increase the density of 3H-imipramine binding sites on platelets by a process which is independent of the uptake of serotonin.

Adolescent↗
PubMed1985

Comparative localization of neurotensin receptors on nigrostriatal and mesolimbic dopaminergic terminals.

Neurotensin (NT), a brain-gut peptide, possesses many biological actions similar to those reported for neuroleptics. Moreover, it has been shown that NT alters dopaminergic activity of both nigrostriatal and mesolimbic pathways. We now report that NT receptors are located on dopaminergic cell bodies in both systems. However, the proportion of NT receptors on presynaptic dopaminergic terminals appears to be different. NT receptor sites are mainly found on presynaptic dopaminergic terminals in the caudate-putamen while they are pre- and post-synaptically located in the nucleus accumbens and the olfactory tubercule. NT receptors differential localization in these two pathways could be used as a model to study the comparative physiology of various dopaminergic brain systems.

Animals↗
PubMed1985

Autoradiographic localization of mu, delta and kappa opioid receptor binding sites in rat and guinea pig spinal cord.

The autoradiographic distribution of mu, delta and kappa opioid binding sites was evaluated in various segments of the rat and guinea pig spinal cord. Mu opioid receptor binding sites are highly concentrated in the superficial layers of the dorsal horn (laminae II and III) in both species, without any marked gradient along the cord. Delta binding sites are somewhat concentrated in the superficial layers of the dorsal horn. However, delta binding sites are also present and evenly distributed in other areas of the gray matter. The highest density of delta sites is found in the cervical segment with only low levels in the lumbo-sacral region of the rat and guinea pig spinal cord. Kappa opioid binding sites are highly concentrated in the superficial layers of the dorsal horn of the spinal cord. Lower levels are seen in the rest of the gray matter with some enrichment in lamina X. Moreover, the lumbo-sacral portion of the spinal cord is enriched in kappa sites as compared to the cervical and thoracic segments. These data demonstrate the differential laminar distribution of mu, delta and kappa opioid binding sites in rat and guinea pig spinal cord.

Animals↗
PubMed1985

Dynorphinergic pathways of Leu-enkephalin production in the rat brain.

Leu-Enkephalin (LE) is an endogenous opioid peptide that can arise from two distinct precursors: proenkephalin and prodynorphin. Experiments were designed to differentiate LE derived from proenkephalin versus that derived from prodynorphin. The most dense collections of dynorphin-positive fibers and terminals are in the substantia nigra and posterior pituitary, areas rich in dynorphin-related peptides. The concentration of LE in these regions is significantly higher than that of ME-Arg-Gly-Leu; the ratio of LE to ME-Arg-Gly-Leu is therefore greater than that found in the proenkephalin precursor, which is unity. Globus pallidus deafferentation resulted in a significant decrease of dynorphin B and LE, but not ME-Arg-Gly-Leu, in the substantia nigra. Mild intermittent foot shock (0.2 mA, 20 min) causes a significant increase of dynorphin B and LE in the substantia nigra, but has no effect on ME-Arg-Gly-Leu concentrations. Thus, in the substantia nigra LE may be derived primarily from prodynorphin. Likewise, in the posterior pituitary, osmotic stimulus (e.g., 2% NaCl as drinking fluid) causes marked depletion in dynorphin and LE but has no effect on ME levels suggesting that in the posterior pituitary LE is derived primarily from dynorphin.

Animals↗
PubMed1985

Multiple tachykinin receptors in guinea pig brain. High densities of substance K (neurokinin A) binding sites in the substantia nigra.

Receptor binding characteristics of labelled substance P (SP) and substance K (SK) were investigated in guinea pig membrane preparations and by in vitro receptor autoradiography. The two ligands bind to single class of sites with Kd of 2.1 nM and Bmax of 37.0 fmol/mg protein for SP and 10.6 nM and 50.3 fmol/mg protein for SK. Ligand selectivity patterns markedly differ for the two ligands. On SP binding sites, SP greater than physalaemin greater than eledoisin greater than SK greater than kassinin greater than Neuromedin K. On the other hand, SK greater than kassinin greater than Neuromedin K greater than eledoisin greater than SP greater than physalaemin on SK binding sites. The autoradiographic distribution of SP and SK binding sites is also different. While the cerebral cortex, substantia nigra and cerebellum contain very low to low densities of SP sites, they are all rich in SK binding sites. These data clearly demonstrate the existence of at least two classes of tachykinin binding sites in guinea pig brain. Moreover, the high density of SK binding sites present in the substantia nigra suggests possible physiological roles for SK in this region.

Animals↗
PubMed1985

Strategies in neuropeptide receptor binding research.

Strategies and general approaches used in neuropeptide receptor binding assays are described. Special attention is given to the nature of the ligand, its physical and chemical stability and the demonstration of an appropriate ligand selectivity pattern. Examples are given to illustrate critical aspects of neuropeptide receptor binding assays. Strong correlation between binding and bioassay data is also stressed.

Animals↗
PubMed1985

Comparative autoradiographic distribution of calcium channel antagonist binding sites for 1,4-dihydropyridine and phenylalkylamine in rat, guinea pig and human brain.

The in vitro autoradiographic distribution of calcium channel antagonist binding sites for 1,4-dihydropyridine and phenylalkylamine has been investigated in rat, guinea pig and human brain. 1,4-dihydropyridine ([3H] (+) PN200-110) and phenylalkylamine ([3H] (-) D-888) binding sites are identically distributed in the brain of the three mammalian species studied. High densities of calcium antagonist binding sites are present in brain areas enriched in synaptic contacts such as the hippocampus, cortex and striatum. Low to moderate densities of sites are found in other regions such as the thalamus, hypothalamus and brain stem. These data demonstrate the existence of specific calcium antagonist binding sites in mammalian brain including man. These sites are discretely distributed with highest concentrations present in the hippocampus and cortex. Moreover, the similar distribution of binding sites for [3H] (+) PN200-110 and [3H] (-) D-188 suggests that 1,4-dihydropyridine and phenylalkylamine bind to the same receptor site complex in mammalian brain.

Amines↗
PubMed1985

Variability of chronic antidepressant treatments on beta-adrenergic receptor sites.

It has been proposed that down-regulation of beta-adrenergic receptors may be related to the therapeutic action of antidepressants. To further characterize the role of beta-adrenergic receptor regulation in the actions of antidepressants, the effects of chronic treatment with desipramine, zimelidine and bupropion on beta-adrenergic receptors in rat brain membrane preparations were studied. Chronic treatment with desipramine, but not zimelidine and bupropion decreased significantly the density of beta-adrenergic receptors. These data suggest that clinically effective antidepressants may vary considerably in their ability to down-regulate beta-adrenergic receptors after chronic treatment.

Animals↗
PubMed1985

Ontogeny and regional distribution of proenkephalin- and prodynorphin-derived peptides and opioid receptors in rat hippocampus.

Levels of prodynorphin- and proenkephalin-derived peptides were determined in whole hippocampus of prenatal and early postnatal rats and in five regions of the hippocampus of the adult rat. Using autoradiography, opioid receptor subtypes were localized in coronal sections of adult hippocampus. The opioid peptides are present in very low concentrations in prenatal hippocampus, with only dynorphin B and alpha-neo-endorphin being present in significant amounts. The main increase in concentrations of the opioid peptides occur between day 7 and 14 postnatally, when dynorphin A, dynorphin A-(1-8), dynorphin B and alpha-neo-endorphin reach their adult levels. beta-Neo-endorphin and [Met]enkephalyl-Arg-Gly-Leu do not reach their maximal level until later in development. There is a distinct differential distribution of the opioid peptides in the subregions of the hippocampus; the subiculum and CA1 are relatively poor in prodynorphin-derived peptides but do contain significant amounts of [Met]enkephalin and [Leu]enkephalin. Very high concentrations of dynorphin B and alpha-neo-endorphin are present in region CA4. Dynorphin A-(1-8) and [Met]enkephalin have their highest concentrations in the dentate gyrus. There is a 5-fold higher concentration of [Met]enkephalin in the ventral hippocampus compared to the dorsal hippocampus. A similar trend is seen with dynorphin A-(1-8) but not with the other opioid peptides. The most abundant opioid receptor population in the hippocampus is of the mu type and it is densest in and around stratum pyramidale of the region CA3. There are relatively few kappa opioid receptors in the rat hippocampus. These results indicate the presence of at least two independent opioid neuronal systems (enkephalin and dynorphin) in rat hippocampus and the presence of mu-, delta- and kappa-opioid receptor subtypes.

Aging↗
PubMed1985

Comparative potencies of calcium channel antagonists and antischizophrenic drugs on central and peripheral calcium channel binding sites.

Dihydropyridines are potent agents on [3H]nitrendipine binding sites in heart and brain membranes. Like the phenylalkylamines, they are slightly more active on heart than on brain [3H]nitrendipine binding sites. On the other hand, the diphenylalkylamines, the diphenylpiperazines and the antischizophrenic drugs of the diphenylbutylpiperdine type are more potent on brain [3H]nitrendipine binding sites. The findings suggest tissue heterogeneity of [3H]nitrendipine binding sites and the possible development of diphenylbutylpiperidine-diphenylbutylpiperazine analogues that could selectively act on brain calcium channel antagonist binding sites.

Animals↗
PubMed1984

Comparative potencies of substance P, substance K and neuromedin K on brain substance P receptors.

The relative potency of substance P, substance K and neuromedin K on [3H]substance P binding has been compared in rat brain membrane preparations. Substance K and neuromedin K, two newly isolated substance P-related mammalian peptides, are very weak competitors for [3H]substance P binding sites. It suggests that these two neuropeptides are not acting on the same receptor type as substance P. Moreover, previous substance P receptor classifications are unlikely to be applicable to brain tachykinin receptor sub-types.

Animals↗
PubMed1984

Pain, nociception and spinal opioid receptors.

Opioid peptides derived from proenkephalin and prodynorphin are differentially distributed in the spinal cord. Proenkephalin peptides are preferentially located in the sacral portion of the cord while prodynorphin peptides are concentrated in the cervical spinal cord. Mu opioid receptor are highly concentrated in superficial layers of the dorsal horn in all the spinal cord. Delta opioid receptor are more diffusely distributed in the gray matter of the spinal cord. These sites are principally located in cervical and thoracic portions of the spinal cord. Kappa opioid receptors are highly concentrated in the superficial layers of the lumbo-sacral spinal cord. Its density decreased in the upper levels of the spinal cord. It appears that mu opioid receptors are indifferentially activated by thermal, pressure and visceral nociceptive inputs. Delta receptors are more likely to be involved in thermal nociception while kappa opioid binding sites are associated to visceral pain nociceptive inputs.

Animals↗