1,721,067 research outputs found
Comparative effects of vasoactive intestinal peptide and secretin on exocrine pancreatic secretion in the cat.
No full textThe stimulatory effect of vasoactive intestinal peptide (VIP) and secretin has been compared on exocrine pancreatic secretion in anaesthetized cats. Both peptides were given by bolus intravenous injection and continuous intravenous infusion. After bolus injection, VIP stimulated pancreatic secretion only weakly. On the contrary, during intravenous infusion, the maximal effect of VIP did not differ significantly from that of secretin. Therefore, while the potency of VIP is always lower than that of secretin, its efficacy appears to be strictly dependent on the mode of administration
Effects of cholecystokinin peptides and neurotensin on dopamine release and metabolism in the rostral and caudal part of the nucleus accumbens using intracerebral dialysis in the anaesthetized rat
No full textBy means of intracerebral microdialysis effects of cholecystokinin peptides and neurotensin administered via the microdialysis probe have been studied on dopamine release and metabolism in the nucleus accumbens and neostriatum of the halothane anaesthetized male rat. Levels of extra cellular dopamine (DA) and its metabolites 3,4 dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were assessed in nuc. accumbens (rostral and caudal part) using high performance liquid chromatography in combination with electrochemical detection. (1) In the rostral part of the nuc. accumbens CCK-8 (10 and 100 ?M), CCK-33 (100 ?M) but not CCK-4 (10 and 100 ?M) increased the levels of DA in the perfusate without increasing the extracellular levels of DOPAC and HVA. (2) In the caudal nuc. accumbens CCK-8 and CCK-4 in concentrations of 10 ?M and 100 ? M of CCK-33 had no effect on DA release and metabolism, since the extracellular levels of DA, DOPAC and HVA were not changed. (3) In the rostral nuc. accumbens perfusion with 10 ?M of neurotensin but not with any other concentration of neurotensin (0.01, 0.1, 1 and 100 ?M) increased the levels of DA in the extracellular fluid. (4) In the caudal nuc. accumbens a 40 min perfusion with neutrotensin produced a concentration dependent increase of the levels of DA in the perfusate (peak action at 10 ? M) which in this case was associated with increases in the extracellular levels of DOPAC and HVA. (5) By means of receptor autoradiography using (3-[(125)I]iodotyrosyl(3)) neurotensin it was found that a 40 min perfusion with this radioligand in the rostral nuc. accumbens reached a total volume of 0.051 mm(3). The diffusion of the radioligand was limited to the rostral or caudal part of the nuc. accumbens depending upon the site of placement of the dialysis probe. The results indicate the existence of cholecystokinin (CCK) receptors in the rostral nuc. accumbens, which are sensitive to CCK-8 and CCK-33 but not to CCK-4, and which facilitate DA release without producing any detectable increase in DA metabolites. In contrast, such receptors do not appear to play a similar role in the regulation of DA release in the caudal nuc. accumbens, where DA terminals contain CCK-like immunoreactivity. Furthermore, the results indicate that neurotensin receptors exist both in the rostral and caudal nuc. accumbens, where they inter alia enhance the release of DA. In the caudal nuc. accumbens these effects of neurotensin are also associated with an increase of DA metabolites, possibly suggesting that in this region neurotensin receptors may also control DA synthesis
The secretory trypsin inhibitor like-peptide, PEC-60 increases dopamine D2 receptor agonist induced inhibition of GABA release in the dorsolateral neostriatum of the awake freely moving rat. An in vivo microdialysis study
No full textThe effects of local perfusion with the secretory trypsin inhibitor like-peptide, PEC-60 on dopamine and γ-aminobutyric acid (GABA) release in the dorsolateral neostriatum and GABA release in the globus pallidus were studied using in vivo microdialysis in the awake freely moving rat. Local perfusion with PEC-60 (500 nM and 1 μM) increased dopamine release in the dorsolateral neostriatum while the highest (1 μM) concentration of PEC-60 decreased striatal but not pallidal GABA release. An inactive form of the peptide, S-carboxyamidomethylated PEC-60 (1 μM) failed to influence either striatal dopamine and GABA or pallidal GABA release. In addition, when PEC-60, at a dose which did not affect striatal and pallidal GABA release (100 nM), was co-perfused together with the dopamine D2 receptor agonist pergolide (500 nM), a potentiation in the ability of pergolide to reduce GABA release in the dorsolateral neostriatum was observed and this effect was counteracted by co-perfusion with the selective dopamine D2 receptor antagonist raclopride (1 μM). In contrast, the pergolide induced inhibition of striatal dopamine release was unaffected by PEC-60 (100 nM). These data indicate that PEC-60 differentially regulates dopamine and GABA release in the dorsolateral neostriatum by a selective and facilitory interaction with the postsynaptic dopamine D2 receptor possibly involving high-affinity PEC-60 like-peptide binding sites located on local axon collaterals of a discrete subpopulation of efferent GABA neurons and/or on GABA intemeurons
Evidence for the existence of receptor--receptor interactions in the central nervous system. Studies on the regulation of monoamine receptors by neuropeptides.
No full textEvidence for the existence of receptor-receptor interactions in the central nervous system. Studies on the regulation of monoamine receptors by neuropeptides.
No full textSubstance P (SP) (10(-8) M) can rapidly reduce the affinity and increase the density of 3H-5-HT binding sites in spinal cord membranes. CCK-8 and CCK-4 (10(-8) M) can rapidly and differentially change the characteristics of 3H-spiperone striatal binding sites linked to DA receptors of the D2 type. CCK-4 increase and CCK-8 reduce the number of striatal binding sites for 3H-spiperone, indicating for the first time separate CCK-4 binding sites. CCK-4 (10(-8) M) but not CCK-8 (10(-8) M) can rapidly reduce the affinity and increase the number of the 3H-spiperone binding sites linked to 5-HT receptors of the dorsal cerebral cortex of rats. CCK-8 (10(-8) M) only produces a trend for a small increase in the Bmax values of these receptors. These results again imply the existence of separate CCK-4 binding sites in this case in the cerebral cortex. Glutamate (10(-6) M), but not N-methyl-D-aspartate (10(-6) M) can rapidly change the characteristics of the 3H-N-propylnorapomorphine (3H-NPA) binding sites in striatal membranes of rats. Glutamate (10(-6) M) increases the density and especially reduces the affinity of the 3H-NPA binding sites, which label D2 and D3 types of DA receptors. Taken together the present findings give evidence that neuropeptide receptors and glutamate receptors can in vitro rapidly modulate the characteristics of different types of DA and 5-HT receptors by way of receptor--receptor interactions at the comodulate level or at the local circuit level. It is hypothesized that these receptor--receptor interactions are of importance for the encoding of short-term memory
Neuropeptide Y in vitro selectivity increases the number of alpha 2-adrenergic binding sites in membranes of the medulla oblongata of the rat.
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PEC-60 increases dopamine but not GABA release in the dorsolateral neostriatum of the halothane anaesthetized rat. An in vivo microdialysis study
No full textThe effect of striatal perfusion with the intestinal peptide PEC-60 on endogenous dopamine (DA) and γ-aminobutyric acid (GABA) release in the dorsolateral striatum and GABA release in the globus pallidus was monitored using in vivo microdialysis in the halothane anaesthetized rat. The results show that PEC-60 (100 nM) increases DA release in the dorsolateral striatum without influencing GABA release in the dorsolateral striatum or in the globus pallidus. In addition, PEC-60 failed to influence the extracellular striatal 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels. The PEC-60 induced increase in striatal DA was abolished by the addition of tetrodotoxin (1 μM) to the perfusion medium. These data suggest that PEC-60 plays a role in modulating striatal DA release but not DA metabolism and that this effect is primarily targeted on the presynaptic DA terminals of the nigrostriatal DA pathway rather than on the postsynaptic striatopallidal GABA projection neurons in the dorsolateral striatum. © 1994
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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