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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 26 (1970), S. 1266-1267 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Résumé Certains neurones hypothalamiques présentent dans la demi-heure qui suit une stimulation vaginale des modifications de leur décharge spontanée indépendantes de l'état de vigilance de l'animal. Ces variations pourraient être en rapport avec les mécanismes nerveux de l'ovulation provoquée chez la Lapine.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 38 (1982), S. 706-707 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intracerebroventricular injections of angiotensin II (A II) induced a sharp and dose-dependent increase in plasma prolactin (PRL) levels in the awake Rhesus monkey. Our results suggest that in primates, A II may be involved in the mechanisms controlling PRL secretion.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Septum ; Supraoptic nucleus ; Vasopressin ; Oxytocin ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to see whether septal neurones are connected to the hypothalamic neurones secreting vasopressin or oxytocin, neurones in different regions of the septum were recorded during electrical stimulation of the supraoptic nucleus. The position of the stimulating electrode within the latter was verified using lactating rats in which milk ejections could be induced by a train of electrical pulses applied to the nucleus. The responses of septal neurones to single pulse stimulation were then analysed by post-stimulus time histograms. In the septum ipsilateral to the site of stimulation, 42% of the neurones were antidromically invaded, 20% were orthodromically excited and 21% were inhibited following supraoptic stimulation. In the contralateral septum, 2% of the cells tested were antidromically invaded, 3% were excited and 16% inhibited. In the medial septum, 14% of the neurones were orthodromically excited, and 48% were inhibited. These results provide electrophysiological evidence for direct connections between septal neurones and the ipsilateral supraoptic nucleus of the hypothalamus, and give further support to the hypothesis of a septal influence on the activity of vasopressin- or oxytocin-releasing cells in the magnocellular system.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Physiology-Paris 88 (1994), S. 403 
    ISSN: 0928-4257
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 48 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The pattern of hydrolysis of [3H]angiotensin II ([3H]AII; 20 nM) by intact cells was studied on cultured mouse spinal cord cells. Degradation products were identified by HPLC analysis after incubation for 2 h at 37°C. In the absence of peptidase inhibitors, 70% of [3H]AII was degraded, and the main labeled metabolite was [3H]tyrosine (40% of total radioactivity). Minor quantities of [3H]AII1–5 and [3H]AII4–8 were formed. Results obtained in the presence of various inhibitors indicate that several enzymes were involved in the All-hydrolyzing process. Dipeptidyl aminopeptidase III (EC 3.4,14.4) could play a critical role, as suggested by the formation of [3H]Val3-Tyr4 and [3H]-Tyr4-IIe5 in the presence of bestatin (2 ± 10−5M). This hypothesis was confirmed by the potency of dipeptidyl aminopeptidase III inhibitors to inhibit both [3H]AII hydrolysis and formation of these 3H-labeled dipeptides. An arylamidase-like activity could also be participating in [3H]AII hydrolysis, because higher concentrations of bestatin (10−4M) in association with dipeptidyl aminopeptidase III inhibitors totally inhibited [3H]tyrosine formation, increased protection of [3H]AII and [3H]AII1–7 formed, and provoked a slight accumulation of [3H]AII2–8. These results suggest that the formation of [3H]AII2–8 is due to the action of a bestatininsensitive acidic aminopeptidase and that the Pro7-Phe8 cleavage is also a step of AII hydrolysis, resulting from the action of an unidentified peptidase different from prolyl endopeptidase. Because care was taken to eliminate interference by enzymes leaking out into the incubation medium, the AII-hydrolyzing process described on these cultured mouse spinal cord cells presumably occurs under the action of membrane-bound peptidases.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: DARPP-32 is a cyclic adenosine monophosphate-regulated inhibitor of protein phosphatase 1, highly enriched in striatonigral neurons. Stimulation of dopamine D1 receptors increases phosphorylation of DARPP-32, whereas glutamate acting on N-methyl-d-aspartate receptors induces its dephosphorylation. Yet, to date, there is little direct evidence for the function of DARPP-32 in striatal neurons. Using a whole cell patch-clamp technique, we have studied the role of DARPP-32 in the regulation of voltage-gated sodium channels in rat striatal neurons maintained in primary culture. Injection of phospho-DARPP-32, but not of the unphosphorylated form, reduced the sodium current amplitude. This effect was similar to those induced by okadaic acid, with which there was no additivity and by tautomycin. Our results indicate that, in striatal neurons, sodium channels are under dynamic control by phosphorylation/dephosphorylation, and that phospho-DARPP-32 reduces sodium current by stabilizing a phosphorylated state of the channel or an associated regulatory protein. We propose that the DARPP-32-mediated modulation of sodium channels, via inhibition of phosphatase 1, contributes to the regulation of these channels by D1 receptors and other neurotransmitters which influence the state of phosphorylation of DARPP-32.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Met-enkephalin and β-endorphin induced a partial reversion of the dopamine inhibition of prolactin release from pituitary cells of lactating rats in primary culture. This effect of opiate peptides was dose-dependent with an EC50 of 40 ± 8 nM and 45 ± 7 nM and maximal blockade of dopamine inhibition of 60% and 68% for Met-enkephalin and β-endorphin, respectively. Naloxone antagonized the effect of Met-enkephalin with an EC50 of 22 ± 12 nM. Furthermore, this Met-enkephalin effect on dopamine inhibition of prolactin secretion appeared non-competitive since it reduced maximal inhibition without affecting the apparent affinity of dopamine. Finally, it should be noted that the two opiate peptides had no effect on spontaneous prolactin release.In electrophysiological experiments, local ejection of dopamine on tested cells induced an hyperpolarization concomitant with an increase of the membrane conductance. Ejection of Met-enkephalin or β-endorphin alone did not modify the electrical properties of the cells (resting potential, membrane conductance and excitability). In contrast, both peptides blocked in a reversible manner the dopamine-induced electrical responses. These effects were antagonized by naloxone. However, this interaction of opiatepeptides with dopamine electrical response was not observed on all cells tested. We conclude that the blocking effect of opiates on dopamine-induced hyperpolarization may account, at least in part, for the ability of these peptides to interact with dopamine inhibition of prolactin release.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 2 (1990), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In this paper evidence is shown that synthetic arginine vasopressin (AVP) can evoke marked in vitro release of endogenous immunoreactive AVP (I-AVP) from male rat septal and hypothalamic tissue superfused in vitro. The stimulatory action was dosedependent with a maximal amplification factor of 2.3 when using 14 pg of synthetic AVP as the stimulus. It was highly specific since only AVP was effective and not three closely related substances such as lysine vasopressin, oxytocin and a 4–9 C fragment of AVP. This reproducible effect of AVP required, however, effective concentrations of bacitracin (10−4 to 10−5 M) in the superfusion medium to inhibit aminopeptidase(s) capable of inactivating AVP. Lastly, the stimulatory action of AVP on its own release was not blocked by a V1-receptor antagonist of AVP but was blocked by a V2-antagonist. It is proposed that this novel and robust positive feedback of AVP on its own release may be involved in the mechanism of memory consolidation of certain behavioral tasks known to be affected by AVP.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This paper describes the release characteristics of arginine vasopressin (AVP) from the dorsal septum and dorsal hippocampus of freely behaving male rats using miniaturized push-pull cannulae and a slow rate of perfusion to minimize tissue damage. The major findings were that) The spontaneous release of immunoreactive AVP (l-AVP) from the dorsal hippocampus was episodic in nature and did not require the presence of bacitracin in the perfusion medium to reliably demonstrate its pattern of release; 2) despite the fact that the septum has close to seven times more I-AVP per/mg of tissue, the dorsal septum perfusates had undetectable levels of the neuropeptide; 3) under these conditions hypertonic saline intraperitoneally did not alter the spontaneous release of this peptide; and 4) only when the perfusion medium contained effective concentrations of bacitracin (10−4 M) were reliable and detectable levels of I-AVP measured in perfusates from the dorsal septum and exogenous synthetic AVP had a robust positive feedback action on its own release. The physiological relevance and importance of this robust and novel effect of AVP remains to be elucidated.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Estrogens are known to affect the functioning of the extrapyramidal motor system. Their actions concern both pre- and postsynaptic components of the dopaminergic nigrostriatal neurotransmission. Postsynaptically, estradiol alters the electrophysiological responses of striatal neurons to dopamine application. The aim of this study was to determine the respective roles of D1 and D2 receptor subtypes in this modification of dopamine action. Eighty-three spontaneously firing caudate neurons of ovariectomized female rats were extracellularly recorded during iontophoretic ejection of dopamine or dopaminergic agonists or antagonists. Between 5 and 10 h after a single 17β-estradiol injection (60 μg/kg), the predominant effect of dopamine was an activation of firing (63%), and the distribution of responses significantly differed from controls and from neurons recorded less than 5 h after estradiol injection (P〈0.001) on which dopamine mainly elicited inhibitory effects (71% and 63%, respectively). The excitatory effects of dopamine on this subset of spontaneously firing striatal neurons were blocked by the D1 antagonist SCH 23390 (56%), whereas the inhibitory actions were antagonized by sulpiride (62%), whose isolated application often had an excitatory effect (54%).The distributions of the responses to specific D1 or D2 agonists were not altered by estrogen treatment: the predominant effect of the D2 agonist RU 24213 was in all groups a reduction of firing rate (54%), and the D1 agonist SKF 38393 mainly induced either a decrease in mean firing rate (21%) or a biphasic effect consisting on an excitation-inhibition sequence (53%).These results suggest that estradiol does not qualitatively alter the coupling of D1 or D2 receptors to their electrophysiological effectors, but rather quantitatively changes the ratio between the D1 and D2 receptor-mediated components of dopamine actions, reinforcing the D1 and/or attenuating the D2 receptor-mediated component.
    Type of Medium: Electronic Resource
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