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  • 1
    Electronic Resource
    Electronic Resource
    Differences in serotonergic neurotransmission between rats displaying high or low anxiety/depression-like behaviour: effects of chronic paroxetine treatment (2005)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 92 (2005), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Disturbances in serotonergic neurotransmission have been suggested to be closely interlinked with hyperactivity of the hypothalamic-pituitary-adrenocortical (HPA) system, and are likely to be involved in the pathophysiology of anxiety disorders and major depression. We therefore investigated markers of serotonergic transmission and their modulation by chronic paroxetine in rats selectively bred for high (HAB) or low (LAB) anxiety-related behaviour, both under basal conditions and in response to emotional stress. Hippocampal serotonin 1 A (5-HT1A) receptor mRNA expression was reduced in HAB rats, whereas 5-HT concentrations in hippocampal microdialysates did not differ between HAB and LAB rats under basal conditions. In the hippocampus, overall expression of serotonin transporter binding sites was increased in HAB compared with LAB rats. Exposure to emotional stress failed to increase intrahippocampal 5-HT release in HAB rats whereas LAB rats displayed a physiological, albeit small rise. Chronic paroxetine treatment markedly increased the stress-induced rise in hippocampal 5-HT in HAB, but not LAB rats. This effect may be (at least in part) related to a greater down-regulation of hippocampal serotonin transporter binding sites by paroxetine in HABs compared with LABs, while 5-HT1A receptor expression remained unaffected in this brain area. The findings indicate reduced hippocampal serotonergic transmission in HAB rats as compared with LAB rats, which is evident both at the presynaptic (5-HT release) and the postsynaptic (5-HT1A receptor) level. Chronic paroxetine enhanced the presynaptic responsivity in HAB rats, but not LAB rats, pointing to a preferential efficacy of paroxetine in rats with enhanced anxiety/depression-related behaviour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02953.x
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  • 2
    Electronic Resource
    Electronic Resource
    Differential effects of phencyclidine application on secretogranin II expression in organotypic slices of rat prefrontal cortex (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 87 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Phencyclidine (PCP) is a non-competitive NMDA glutamate receptor antagonist that induces psychotomimetic effects in humans and experimental animals. Chronic PCP exposure elicits signs of persistently altered frontal brain activity and related behaviors which are also seen in patients with schizophrenia. Secretogranin II (sg II) belongs to the chromogranin family of proteins that exist in large dense core vesicles in nervous tissue. In the brain, 90% of sg II is processed to the small peptide secretoneurin. We previously detected differential effects of single-dose and subchronic PCP administration on sg II expression in the rat prefrontal cortex (PFC). In the present study, we applied PCP to organotypic PFC slices. PCP application for 28 h induced decreased tissue and culture medium secretoneurin content. In contrast, incubation with the adenylate cyclase activator forskolin caused significantly increased secretoneurin levels after 8 h. PCP for 4 h followed by 24 h without PCP resulted in increased culture medium secretoneurin content but no change in tissue levels. sg II mRNA expression was decreased after 28 h PCP application in cortical neurons. Immunohistochemical and TUNEL staining profiles indicated that the alterations were not due to neurodegeneration. PCP for 5 days changed neither the secretoneurin tissue or culture medium levels, nor the sg II mRNA expression. These results demonstrate that PCP modulates sg II expression in PFC tissue in the absence of afferent inputs and that the nature of these changes is dependent upon the duration of exposure to and/or withdrawal from PCP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.01989.x
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  • 3
    Electronic Resource
    Electronic Resource
    Taurine selectively modulates the secretory activity of vasopressin neurons in conscious rats (2001)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 14 (2001), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous experiments have shown that a 10-min forced swimming session triggers the release of vasopressin from somata and dendrites, but not axon terminals, of neurons of the hypothalamic–neurohypophysial system. To further investigate regulatory mechanisms underlying this dissociated release, we forced male Wistar rats to swim in warm (20 °C) water and monitored release of the potentially inhibitory amino acids gamma amino butyric acid (GABA) and taurine into the hypothalamic supraoptic nucleus using microdialysis. Forced swimming caused a significant increase in the release of taurine (up to 350%; P 〈 0.05 vs. prestress release), but not GABA. To reveal the physiological significance of centrally released taurine, the specific taurine antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide was administered into the supraoptic nucleus via retrodialysis. Administration of this antagonist caused a significant increase in the release of vasopressin within the supraoptic nucleus and into the blood both under basal conditions and during stress (up to 800%; P 〈 0.05 vs. basal values), without affecting hypothalamic or plasma oxytocin. Local administration of the GABAA receptor antagonist bicuculline, in contrast, failed to influence vasopressin secretion at either time point. In a separate series of in vivo electrophysiological experiments, administration of the same dosage of the taurine antagonist into the supraoptic nucleus via microdialysis resulted in an increased electrical activity of identified vasopressinergic, but not oxytocinergic, neurons. Taken together our data demonstrate that taurine is released within the supraoptic nucleus during physical/emotional stress. Furthermore, at the level of the supraoptic nucleus, taurine inhibits not only the electrical activity of vasopressin neurons but also acts as an inhibitor of both central and peripheral vasopressin secretion during different physiological states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.0953-816x.2001.01729.x
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  • 4
    Electronic Resource
    Electronic Resource
    Vasopressin from hypothalamic magnocellular neurons has opposite actions at the adenohypophysis and in the supraoptic nucleus on ACTH secretion (2002)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 16 (2002), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Magnocellular vasopressinergic and oxytocinergic neurons of the hypothalamic supraoptic (SON) and paraventricular nuclei comprise the hypothalamic–neurohypophysial system, which is crucially involved in the regulation of body fluid and electrolyte homeostasis. However, still controversial is to what extent the same system influences the secretion of adrenocorticotropic hormone (ACTH) from the adenohypophysis. Therefore, we selectively stimulated magnocellular neurons of the SON of conscious male Wistar rats via retrodialysis. As expected, dialysis of the SON with hypertonic medium increased both the release of vasopressin within the SON and the secretion of vasopressin and oxytocin into the systemic blood circulation. This activation of the hypothalamic–neurohypophysial system was accompanied by a fivefold increase in plasma ACTH concentration. This effect was observed only if the tip of the microdialysis probe was within the SON. Intravenous infusion of the vasopressin V1 receptor antagonist d(CH2)5Tyr(Me)AVP significantly attenuated the effects of local osmotic stimulation of the SON on ACTH secretion. In contrast, administration of the same antagonist directly into the SON significantly enhanced the osmotically stimulated secretion of ACTH and corticosterone, primarily by delaying the restoration of the hormone secretion to prestimulation levels. We conclude from these findings that vasopressin from the hypothalamic–neurohypophysial system participates in the regulation of the hormonal stress response in a counterbalanced manner at the level of the SON and the adenohypophysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2002.02101.x
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  • 5
    Electronic Resource
    Electronic Resource
    GABA selectively controls the secretory activity of oxytocin neurons in the rat supraoptic nucleus (2004)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 19 (2004), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Recently we reported that a single social defeat experience triggers the release of oxytocin (OXT) from somata and dendrites, but not axon terminals, of neurons of the hypothalamic–neurohypophysial system. To further investigate the regulatory mechanisms underlying this dissociated release, we exposed male Wistar rats to a 30-min social defeat and monitored release of the inhibitory amino acids gamma amino butyric acid (GABA) and taurine within the hypothalamic supraoptic nucleus (SON) using microdialysis. Social defeat caused a significant increase in the release of both GABA and taurine within the SON (up to 480%; P 〈 0.01 vs. prestress release). To reveal the physiological significance of centrally released GABA, the specific GABAA-receptor antagonist bicuculline (0.02 mm) was administered into the SON via retrodialysis. This approach caused a significant increase in the release of OXT both within the SON and into the blood under basal conditions and during stress (up to 300 and 200%, respectively; P 〈 0.05 vs. basal values), without affecting plasma vasopressin. Electrophysiological studies confirmed the selective action of bicuculline on the firing activity of OXT neurons in the SON. Taken together, our data demonstrate that GABA is released within the SON during emotional stress to act as a selective inhibitor of both central and peripheral OXT secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2004.03151.x
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  • 6
    Electronic Resource
    Electronic Resource
    Reduced anxiety and improved stress coping ability in mice lacking NPY-Y2 receptors (2003)
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 18 (2003), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neuropeptide Y (NPY) has been implicated in the pathophysiology of certain mood disorders, including depression and anxiety. It is, however, not known which of the five cloned NPY receptors mediate these functions. We investigated the effect of Y2 receptor deletion on anxiety and stress-related behaviours. In the elevated plus maze, Y2 knock out (Y2−/−) mice showed a 2.7-fold higher frequency of entering into, and spent 3.8 times more time within, the open arms compared to controls, while entries into the closed arms did not differ. Similarly Y2−/− mice entered the central area of the open field 1.7 times more frequently and also spent 1.8 times more time there. In the light/dark test Y2−/− mice had a 4.8-fold lower latency to enter the lit area but stayed there 2.6 times longer than control mice. Y2−/− mice displayed 3.2-fold less immobility in the forced swim test, indicating improved stress coping ability. Y2 receptors are predominantly located presynaptically where they mediate feedback inhibition of neurotransmitter release. Deletion of these receptors may result in enhanced release of NPY, GABA and/or glutamate in brain areas linked to the manifestation of anxiety, and stress-related behaviour such as the amygdala. Taken together, deletion of the Y2 receptor has revealed an important role of Y2 receptors in the generation of anxiety-related and stress-related behaviours in mice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2003.02725.x
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  • 7
    Electronic Resource
    Electronic Resource
    Acute transcranial magnetic stimulation of frontal brain regions selectively modulates the release of vasopressin, biogenic amines and amino acids in the rat brain (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Using intracerebral microdialysis in urethane-anaesthetized adult male Wistar rats, we monitored the effects of acute repetitive transcranial magnetic stimulation (rTMS; 20 trains of 20 Hz, 2.5 s) on the intrahypothalamic release of arginine vasopressin (AVP) and selected amino acids (glutamate, glutamine, aspartate, serine, arginine, taurine, γ-aminobutyric acid) and the intrahippocampal release of monoamines (dopamine, noradrenaline, serotonin) and their metabolites (homovanillic acid, 3,4-dihydroxyphenylacetic acid, 5-hydroxyindoleacetic acid). The stimulation parameters were adjusted according to the results of accurate computer reconstructions of the current density distributions induced by rTMS in the rat and human brains, ensuring similar stimulation patterns in both cases. There was a continuous reduction in AVP release of up to 50% within the hypothalamic paraventricular nucleus in response to rTMS. In contrast, the release of taurine, aspartate and serine was selectively stimulated within this nucleus by rTMS. Furthermore, in the dorsal hippocampus the extracellular concentration of dopamine was elevated in response to rTMS. Taken together, these data provide the first in vivo evidence that acute rTMS of frontal brain regions has a differentiated modulatory effect on selected neurotransmitter/neuromodulator systems in distinct brain areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00243.x
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  • 8
    Electronic Resource
    Electronic Resource
    Release of Serotonin in the Rat Locus Coeruleus: Effects of Cardiovascular, Stressful and Noxious Stimuli (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of neuroscience 9 (1997), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: To investigate the function of serotonergic neurons within the locus coeruleus, this brain nucleus of conscious, freely moving rats was superfused with artificial cerebrospinal fluid through a push-pull cannula and the extracellular concentration of serotonin was determined in the superfusate. Serotonin release was increased by depolarization with veratridine (5 μM) or 80 mM K+, while superfusion with tetrodotoxin (1 μM) or systemic administration of 8–hydroxy-2–(di-n-propylamino)tetralin substantially diminished the release rate of serotonin in the locus coeruleus. The pressor response to intravenous infusion of noradrenaline (4 μg/kg/min) was associated with a pronounced increase in the release rate of serotonin. Superfusion of the locus coeruleus with tetrodotoxin (1 μM) abolished the increase in serotonin release evoked by the pressor response. A fall of blood pressure produced by intravenous administration of nitroprusside (150 μg/kg/min) or chlorisondamine (3 mg/kg) diminished the release rate of serotonin. Immobilization, noise (95 dB) or tail pinch increased the release of serotonin in the locus coeruleus and slightly elevated blood pressure. Chlorisondamine abolished the rise in blood pressure elicited by tail pinch without influencing the increased serotonin release. Tail pinch-induced serotonin release was abolished by superfusion with tetrodotoxin. The findings demonstrate that neuronal serotonin release in the locus coeruleus responds to cardiovascular and sensory stimuli, suggesting a function of serotonergic neurons in central blood pressure regulation, as well as in the modulation of locus coeruleus activity by stress and noxious stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.1997.tb01632.x
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  • 9
    Electronic Resource
    Electronic Resource
    Inhibition of catecholamine (noradrenaline, dopamine) release in the locus coeruleus and the hypothalamus by baroreceptor activation: identification of the involved baroreceptors (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 291-296 
    Details
    ISSN: 1432-1912
    Keywords: Posterior hypothalamus ; Locus coeruleus ; Noradrenaline ; Dopamine ; Blood pressure ; Aortic depressor nerve ; Baroreceptor reflex ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that experimentally induced blood pressure changes modify the release rates of catecholamines in the hypothalamus and the locus coeruleus. The aim of the present investigation was to identify the peripheral baroreceptors and the centripetal pathways responsible for the changes of catecholamine release in these brain areas. In anaesthetized cats, push-pull cannulae were bilaterally inserted into the locus coeruleus and the posterior hypothalamus. The two brain areas were superfused simultaneously with artificial cerebrospinal fluid. Baroreceptor activation by phenylephrine-induced blood pressure elevation decreased the release rate of noradrenaline in the locus coeruleus and the release rates of noradrenaline and dopamine in the posterior hypothalamus. Similar effects were elicited by electrical stimulation of the central trunk of the transected vagus and aortic depressor nerves (vagus-ADN). Transection of the nerves abolished the effect of phenylephrine on the release of noradrenaline in the locus coeruleus. Nerve transections attenuated slightly the decreased release of noradrenaline elicited by phenylephrine in the posterior hypothalamus, while the reduced dopamine release rate was not influenced. The selective stimulation of baroreceptors in the carotid sinus by an inflatable catheter did not influence the release of catecholamines in the locus coeruleus, while release rates of noradrenaline and dopamine in the posterior hypothalamus were decreased. The simultaneous superfusion of locus coeruleus and hypothalamus revealed that, in both areas, noradrenaline release is inhibited by baroreceptor activation. Noradrenergic neurons of the posterior hypothalamus are inhibited by baroreceptor impulses conducted by the carotid sinus nerve and vagus-ADN, while the noradrenergic neurons of the locus coeruleus seem to respond to impulses transmitted by vagus-ADN. Furthermore, baroreceptor activation inhibits dopaminergic neurons in the hypothalamus but not in the locus coeruleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00168559
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  • 10
    Electronic Resource
    Electronic Resource
    Inhibition of catecholamine (noradrenaline, dopamine) release in the locus coeruleus and the hypothalamus by baroreceptor activation: identification of the involved baroreceptors (1995)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 352 (1995), S. 291-296 
    Details
    ISSN: 1432-1912
    Keywords: Key words Posterior hypothalamus ; Locus coeruleus ; Noradrenaline ; Dopamine ; Blood pressure ; Aortic depressor nerve ; Baroreceptor reflex ; Push-pull cannula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have previously shown that experimentally induced blood pressure changes modify the release rates of catecholamines in the hypothalamus and the locus coeruleus. The aim of the present investigation was to identify the peripheral baroreceptors and the centripetal pathways responsible for the changes of catecholamine release in these brain areas. In anaesthetized cats, push-pull cannulae were bilaterally inserted into the locus coeruleus and the posterior hypothalamus. The two brain areas were superfused simultaneously with artificial cerebrospinal fluid. Baroreceptor activation by phenylephrine-induced blood pressure elevation decreased the release rate of noradrenaline in the locus coeruleus and the release rates of noradrenaline and dopamine in the posterior hypothalamus. Similar effects were elicited by electrical stimulation of the central trunk of the transected vagus and aortic depressor nerves (vagus-ADN). Transection of the nerves abolished the effect of phenylephrine on the release of noradrenaline in the locus coeruleus. Nerve transections attenuated slightly the decreased release of noradrenaline elicited by phenylephrine in the posterior hypothalamus, while the reduced dopamine release rate was not influenced. The selective stimulation of baroreceptors in the carotid sinus by an inflatable catheter did not influence the release of catecholamines in the locus coeruleus, while release rates of noradrenaline and dopamine in the posterior hypothalamus were decreased. The simultaneous superfusion of locus coeruleus and hypothalamus revealed that, in both areas, noradrenaline release is inhibited by baroreceptor activation. Noradrenergic neurons of the posterior hypothalamus are inhibited by baroreceptor impulses conducted by the carotid sinus nerve and vagus-ADN, while the noradrenergic neurons of the locus coeruleus seem to respond to impulses transmitted by vagus-ADN. Furthermore, baroreceptor activation inhibits dopaminergic neurons in the hypothalamus but not in the locus coeruleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00168559
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