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  • 1
    Electronic Resource
    Electronic Resource
    Effects of α2- and β-adrenoceptor agonists on growth hormone secretion following lesion of the noradrenergic system of the rat (1992)
    Springer
    Neurochemical research 17 (1992), S. 1255-1260 
    Details
    ISSN: 1573-6903
    Keywords: GH ; DSP4 ; 6-OHDA ; MFB ; lesion ; clonidine ; isoproterenol ; PVN
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present investigation was to lesion the noradrenergic system and to measure the effect on growth hormone (GH) secretion following peripheral administration of α2- and β-adrenoceptor agonists. Direct injection of these agonists into the paraventricular nucleus of the hypothalamus (PVN) and its effect on GH secretion were also investigated. Systemic administration of N-2-chloroethyl-N-ethyl-2-bromobenzylamine (DSP4, 60 mg/kg, injected i.p. 10 days prior to experimentation) significantly decreased the noradrenaline (NA) content of the hippocampus, frontal cortex and hypothalamus but had no effect on the dopamine (DA) or serotonin (5-HT) content of these areas. Bilateral injection of 6-hydroxydopamine (6-OHDA, 10 μg/μl, 14 days prior to experimentation) into the medial forebrain bundle (MFB) caused a greater reduction of NA and also decreased the DA and 5-HT content of the hypothalamus. Analysis of the PVN of the hypothalami of rats following 6-OHDA lesion of the MFB showed significantly decreased NA and 5-HT content. Neither DSP4 treatment nor 6-OHDA lesion of the MFB affected the clonidine (250 μg/kg, i.p.) induced stimulation of GH secretion. Injection of isoproterenol (1 mg/kg, i.p.) had varying effects on GH secretion. It stimulated GH release in control rats but not in DSP4 or MFB lesioned rats. Direct injection of clonidine (0.1 μg/μl) into the PVN significantly stimulated GH secretion, whereas injection of isoproterenol (2.5 μg/μl) into the PVN did not affect GH levels when compared to controls. The results of the present study do not support the hypothesis that hypoactivity of the central noradrenergic system may be the cause of the blunted GH response to clonidine observed in depressed patients.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00968409
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    α2 and β-adrenergic stimulation of corticosterone secretion in rats (1993)
    Springer
    Neurochemical research 18 (1993), S. 159-164 
    Details
    ISSN: 1573-6903
    Keywords: Corticosterone ; medial forebrain bundle ; lesion ; clonidine ; isoproterenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Bilateral injection of 6-hydroxydopamine into the medial forebrain bundle (MFB) significantly decreased monoamine concentrations in the hypothalamus. The noradrenaline and serotonin content of the paraventricular nucleus (PVN) was also significantly reduced. These drastic decreases in neurotransmitter concentration did not alter basal secretion of corticosterone. Isoproterenol. a β-adrenoceptor agonist (1 mg/kg, i.p.), significantly stimulated corticosterone release in saline and MFB lesioned rats. This stimulation did not differ significantly between the two groups. Clonidine, an α2-adreceptor agonist, injected either intraperitoneally or intracerebrally just dorsal to the PVN, caused a dose-dependent increase in corticosterone secretion. The stimulation of corticosterone release by clonidine (250 μg/kg, i.p.) was antagonised by the selective α2-adreceptors antagonist, yohimbine (1 mg/kg, i.p.) and significantly reduced by the MFB lesion. These results suggest that corticosterone secretion is stimulated by activation of α2-adreceptors which occur on noradrenergic nerve terminals in the PVN.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01474679
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of intrahippocampal injection of kainic acid on corticosterone release in rats (1990)
    Springer
    Neurochemical research 15 (1990), S. 495-499 
    Details
    ISSN: 1573-6903
    Keywords: HPA axis ; hippocampus ; corticosterone ; kainic acid ; pyramidal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to investigate whether the hiopocampus exerts a modulatory effect on the activity of the hypothalamic-pituitary-adrenal (HPA) axis. Kainic acid was stereotaxically injected into the CA1 pyramidal cell layer of the dorsal hippocampus, causing histological and behavioural changes typical of kainic acid toxicity. The CA3 pyramidal cells of the dorsal hippocampus were selectively lesioned. Rats treated with kainic acid were hyperactive, executed clockwise rotatory movements and displayed epileptic seizures. The acute excitatory effect of kainic acid on glutamatergic receptors in the hippocampus resulted in an elevation in plasma corticosterone levels, suggesting a stimulation of HPA axis activity. Direct or indirect stimulation of the CA1 pyramidal cells of the dorsal hippocampus appeared to have caused the increase in corticosterone secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00966206
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    Paper (German National Licenses)
    Fulltext
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