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Biomedical subjects

K Fuxe

Publications and source records attributed to K Fuxe.

At least 451 records · Page 25Linked to original sources
PubMed1987

Effects of acute and chronic treatment with imipramine on 5-hydroxytryptamine nerve cell groups and on bulbospinal 5-hydroxytryptamine/substance P/thyrotropin releasing hormone immunoreactive neurons in the rat. A morphometric and microdensitometric analysis.

Groups of male rats were treated for a period of 14 days with imipramine (10 mumol/kg) given twice daily. Separate groups of rats received a single dose treatment using the same dose and experimental design as for the repeated treatment. Employing the avidin-biotin immunoperoxidase technique for immunohistochemistry 5-hydroxytryptamine (5-HT)-, substance P(SP)- and thyrotropin releasing hormone (TRH)-like immunoreactivities (IRs) were visualized in consecutive coronal sections of the brain stem and of the spinal cord. The IRs were studied by means of morphometric and microdensitometric procedures using automatic image analysis on profiles representing nerve terminal networks of the ventral horn of the cervical and lumbar enlargements of the spinal cord as well as their coexistence (5-HT/SP and 5-HT/TRH). With the same technique 5-HT IR was measured in the 5-HT nerve cell groups of the medulla oblongata (B1, B2, B3) and of the nucleus raphe dorsalis (B7) of the midbrain. In addition 5-HT and 5-hydroxyindolacetic acid (5-HIAA) levels were measured in the ventral and dorsal horns of the cervical and lumbar enlargements of the spinal cord using high performance liquid chromatography (HPLC). In the same parts of the spinal cord SP IR was studied by means of radioimmunoassay (RIA). The microdensitometric studies showed that chronic, but not acute, imipramine treatment selectively increased SP IR in the 5-HT/SP/TRH costoring nerve terminals of the medial part of the ventral horn in both the cervical and the lumbar enlargements. Furthermore, quantitative analysis of the entity of coexistence in the 5-HT nerve terminals networks of these areas showed that all the 5-HT nerve terminals contained SP and TRH IRs and that this phenomenon remained after acute and chronic imipramine treatment. The microdensitometric studies on the 5-HT nerve cell groups of the medulla oblongata and of the nucleus raphe dorsalis demonstrated that chronic, but not acute, imipramine treatment selectively increased 5-HT IR in the nerve cell bodies of the lateral part of group B3 as evaluated from the median grey values. Acute, but not chronic, imipramine treatment significantly increased the field area of 5-HT IR of nerve cell bodies in group B7, reflecting an increase in the mean profile area of the 5-HT IR nerve cell body profiles. Instead, the mean profile area of 5-HT IR cell bodies of group B1 was acutely reduced by imipramine.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Studies on the cellular localization and distribution of glucocorticoid receptor and estrogen receptor immunoreactivity in the central nervous system of the rat and their relationship to the monoaminergic and peptidergic neurons of the brain.

By means of monoclonal antibodies against the rat liver glucocorticoid receptor (GR) and the human estrogen receptor (ER), in combination with an immunocytochemical analysis, it has been possible to map out GR and ER immunoreactive (IR) neurons in the rat central nervous system and GR IR glial cells in the white matter. The GR IR is located in the cytoplasm and especially in the nucleus while the ER IR is only demonstrated in the nuclei of the neurons. Upon adrenalectomy the GR IR appears to be present exclusively in the cytoplasm, while after castration the ER IR is still exclusively present in the nuclei. Upon corticosterone treatment of the adrenalectomized rat the GR IR is again predominantly found in the nuclei of the neurons. These results indicate that the occupied GR and the unoccupied and occupied ER are located in the nuclei and the unoccupied GR in the cytoplasm. Evidence has been presented that large numbers of monoamine and peptide nerve cell bodies contain GR IR. Furthermore, neuronal GR IR is found in neuronal populations all over the central nervous system, especially in the cerebral cortex, the thalamus and the hypothalamus, indicating a major role of GR in regulating the metabolic and synaptic functions of the brain. The ER IR is instead limited to certain neuronal populations, mainly those of the preoptic area, the bed nucleus of the striae terminalis and the arcuate nucleus, suggesting a specific role in control of LHRH secretion and reproductive behaviour.

Adrenalectomy↗
PubMed1987

Further studies on the effects of central administration of neuropeptide Y on neuroendocrine function in the male rat: relationship to hypothalamic catecholamines.

Following intraventricular (i.v.t.) administration of increasing doses of neuropeptide Y (NPY; 7.5-750 pmol/rat) the catecholamine levels and turnover were quantitatively measured in discrete hypothalamic regions by means of histofluorometry. In the same rats the adenohypophyseal hormones as well as vasopressin, aldosterone (ALDO) and corticosterone (CORTICO) levels in serum were determined. Neuropeptide Y seems to induce a biphasic change in amine utilization in the tuberoinfundibular dopamine (DA) neurons and in the noradrenergic (NA) utilization in various hypothalamic areas. Thus, the lowest doses seem to inhibit the catecholamine utilization while higher doses seem to enhance it. NPY (250-750 pmol) reduced the serum levels of thyreotropine (TSH), prolactin (PRL) and growth hormone (GH) but increased CORTICO, adrenocorticotropin (ACTH) and ALDO serum levels. In conclusion, it is suggested that the NPY induced changes in DA utilization in the tuberoinfundibular DA neurons may contribute to the NPY induced changes in PRL and TSH secretion. The increases in paraventricular NA utilization may contribute to the increases in ACTH, ALDO and CORTICO secretion induced by NPY. These data give further support for NPY as an important neuroendocrine modulator.

Aldosterone↗
PubMed1987

Evidence for discrete alterations in central cardiovascular catecholamine and neuropeptide Y immunoreactive neurons in aged male rats and in genetically hypertensive male rats of the Lyon strain.

A computer-assisted morphometrical and microdensitometrical analysis has been performed on cardiovascular noradrenaline (NA), adrenaline (A) and neuropeptide (Y (NPY) neurons in adult and 24-month-old male rats and on hypotensive (LL), normotensive (LN) and hypertensive (LH) male rats of the Lyon strain using the indirect immunoperoxidase procedures. It was found that in NPY/phenylethanolamine-N-methyltransferase (PNMT) costoring neurons of the CI area of the rostral medulla oblongata NPY-like immunoreactivity showed a more marked reduction than the PNMT immunoreactivity. Furthermore, within the parvocellular part of the paraventricular hypothalamic nucleus. NPY immunoreactive nerve terminal profiles were much more affected than the PNMT immunoreactive profiles during aging as revealed by a marked reduction in the number of profiles and by a marked reduction of absorbency values in the microdensitometrical analysis. Thus, in the NPY/PNMT costoring neurons of the A C1 group of the ventrolateral medulla projecting, for example, to the hypothalamus, the peptide transmission line may have a special vulnerability to the aging processes which may contribute to the development of hypertension in old people in view of a vasodepressor role of many central NPY/PNMT neurons. An extensive morphometrical and microdensitometrical analysis of the various catecholamine (CA) cell groups of the medulla oblongata of the LL, LN and LH rats of the Lyon strain was performed. In a comparison between LL and LH rats the A2 cell group of the LH strain showed a trend for an increase in the mean tyrosine hydroxylase (TH) immunoreactive cell body area and the C3 group showed a significant increase in the number of PNMT immunoreactive profiles.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Intravenous administration of atriopeptin III affects arterial blood pressure differentially in young and old male rats.

The effects of intravenous administration of various doses of atriopeptin III (0.4-36 nmol kg-1) on arterial blood pressure, urinary flow and Na+ and K+ excretion were analysed in awake animals. A dose-related reduction of arterial blood pressure was obtained in 4- and 24-month-old unrestrained, freely moving male rats. A dose-related increase in the diuresis and in sodium and potassium excretion was present in both young and old rats. The hypotensive action was significantly prolonged in the aged animals, indicating possible alterations in the control of the cardiovascular system by the endocrine activity of the heart in the old animal.

Aging↗
PubMed1987

Effects of subacute treatment with toluene on cerebrocortical alpha- and beta-adrenergic receptors in the rat. Evidence for an increased number and a reduced affinity of beta-adrenergic receptors.

Subacute treatment with toluene (80-1500 p.p.m.) produces a dose-dependent reduction of affinity and increase in density of the beta-adrenergic antagonist [3H]dihydroalprenolol binding sites in the frontoparietal cortex of the male rat, while the binding characteristics of alpha 1-adrenergic ([3H]WB 4101) and alpha 2-adrenergic ([3H]p-aminoclonidine) binding sites in the same region is unaffected by this treatment as evaluated in vitro. Therefore, it is suggested that the cortical beta-adrenergic receptors are particularly vulnerable to the action of toluene in vivo. It is speculated that as a result cortical beta-adrenergic neurotransmission may be altered following exposure to low concentrations of toluene, possibly related to the physico-chemical properties of toluene, leading to changes in membrane fluidity.

Animals↗
PubMed1987

Differential effect of ganglioside GM1 on rat brain phosphoproteins: potentiation and inhibition of protein phosphorylation regulated by calcium/calmodulin and calcium/phospholipid-dependent protein kinases.

The monosialoganglioside GM1 displays complex effects on protein phosphorylation of rat cerebral cortex membrane preparations. The exogenous ganglioside at a concentration of 350 microM in absence of calcium only stimulated the phosphorylation of a protein of MW = 64,000. In presence of 1 mM calcium a twofold effect is observed irrespective of the phosphoprotein considered. In particular there is an enhancement of 32P incorporation in four major phosphoproteins of MW = 160,000, 140,000, 64,000 and 50,000 in presence of GM1 compared with that observed with calcium alone. The maximal stimulating effect is achieved with a ganglioside concentration of 35 microM. This effect is inhibited by the addition of 100 microM trifluoperazine (TFP), a phenothiazine known to inhibit calmodulin and protein kinase-C activities. These four proteins represent the major substrates for the calcium/calmodulin-dependent protein kinase with the MW = 64,000 and 50,000 proteins co-migrating with the autophosphorylated subunits of this enzyme. In addition, the ganglioside inhibited the phosphorylation of three proteins with MW = 86,000, 20,000 and 14,000. The electrophoretic properties of these phosphoproteins are similar to the autophosphorylated form of protein kinase-C and to the rat myelin basic proteins, respectively. The effect of the ganglioside on their phosphorylation is not influenced by TFP. Finally, a protein with an apparent molecular weight of 46,000 shows also an increased phosphorylation in presence of GM1. The reported results indicate that exogenous GM1 can have profound effects on different kinases such as the calcium/calmodulin dependent protein kinase, the protein kinase-C and also some unknown calcium-independent protein kinases.

Animals↗
PubMed1987

Effects of intraventricular injections of galanin on neuroendocrine functions in the male rat. Possible involvement of hypothalamic catecholamine neuronal systems.

Galanin-catecholamine interactions have been analysed within the hypothalamus and the anteromedial frontal cortex of male rats by means of quantitative histofluorimetrical and biochemical measurements of catecholamine fluorescence in discrete catecholamine nerve terminal systems and measurements of serum levels of adenohypophyseal hormones and corticosterone using radio-immunoassay determinations. 125I-galanin binding sites were analysed and related to the distribution of galanin-immunoreactive neuronal structures in the median eminence and paraventricular hypothalamic nucleus. The results show that intraventricular injections of galanin in the awake and unrestrained male rat produce rapid increases of prolactin and growth hormone secretion but no effects on serum luteinizing hormone, thyroid stimulating hormone or on corticosterone levels. These changes in neuroendocrine function were associated with a selective reduction of the catecholamine stores in the medial palisade zone of the median eminence at the 20 min time interval. 125I-galanin binding sites were found throughout the hypothalamus including the median eminence and the magnocellular part of the paraventricular hypothalamic nucleus with a good correspondence with galanin immuno-reactivity. It is suggested that the enhancement of prolactin secretion induced by galanin involves an interaction between galanin and dopamine in the medial palisade zone leading to a reduced synthesis and/or release of dopamine and thus to a reduced prolactin inhibitory activity and to increases in prolactin secretion. A possible involvement of hypothalamic catecholamines in the galanin-induced changes of growth hormone secretion remains to be established.

Animals↗
PubMed1987

Effects of subacute toluene exposure on protein phosphorylation levels in rat frontoparietal and striatal membranes.

Effects of subacute toluene exposure (80 p.p.m. toluene in air, 5 + 4 days, 6 h day-1) were analysed on calcium (Ca2+)- and cyclic adenosine monophosphate (cAMP)-induced protein phosphorylation levels in membrane preparations from the frontoparietal cortex and the striatum of the adult male rat. After protein separation by gel electrophoresis, the amount of radioactive phosphate incorporated from adenosine 5'-[gamma-32P] triphosphate, tetra-(ethylammonium) salt ([32P]ATP) was measured indirectly by autoradiography. The 21 most phosphorylated protein bands were then analysed by computerized image analysis. In the frontoparietal cortex no protein bands were significantly affected after cAMP-induced back phosphorylation, while after Ca2+ stimulation there was a decreased incorporation of [32P]ATP in a 22,000 protein band. In the striatum there was a reduced incorporation of [32P]ATP in a 26,000 protein band after cAMP-induced back phosphorylation, and in four bands of 20,000, 21,000, 52,000 and 134,000, respectively, after Ca2+ stimulation. The reduced incorporation of [32P]ATP in these proteins indicated increased original phosphorylation levels after toluene exposure. A comparison between the frontoparietal cortex and the striatum showed a selective vulnerability of phosphorylation processes in striatal membrane protein bands. In conclusion, toluene exposure at low doses augments membrane protein phosphorylation levels in the rat forebrain and especially in the striatum, probably leading to changes in information handling and/or metabolic changes.

Animals↗
PubMed1987

Central catecholamine-neuropeptide Y interactions at the pre- and postsynaptic level in cardiovascular centers.

Central catecholamine (CA)-neuropeptide Y (NPY) interactions and their regulation by glucocorticoids have been analyzed in vivo and in vitro, especially in the dorsal cardiovascular center of the medulla oblongata, including the nucleus tractus solitarius (nTS), using immunocytochemical, receptor autoradiographical, biochemical, and physiological techniques. Intraventricular (i.v.t.) injections of NPY in a low (7.5 pmol) or a high (1.25 nmol) dose increased adrenaline levels 4 h later in the caudal part of the dorsomedial medulla. Furthermore, NPY immunoreactivity (IR) tended to decrease in the rostral part of the dorsomedial medulla 5 min after injection of clonidine (1 microgram) in the alpha-chloralose anaesthetized rat. Thus, presynaptic interaction between NPY and adrenaline (A) mechanisms may exist in the dorsal cardiovascular center taking place at the network local circuit level or the membrane level of the NPY/A costoring synapses of the dorsomedial medulla. In vitro NPY (10 nM) reduced the affinity of the alpha 2-adrenergic agonist binding sites in the nTS, and clonidine (10 nM) reduced the 125I-NPY binding in the dorsomedial medulla. These results indicate the existence of postsynaptic receptor-receptor interactions between alpha 2-adrenergic and NPY receptors in the dorsal cardiovascular center. This interaction may in part take place at the level of the Ni protein, since NPY (300 nM) inhibited cyclic AMP (cAMP) accumulation in slices of the dorsomedial medulla. However, the interactions also probably take place at the proteins carrying the recognition sites, since NPY and adrenaline together given i.v.t. significantly antagonized the hypotensive effects of one another. Thus, the reduced affinity of the alpha 2-adrenergic receptor induced by NPY may reflect a reduced efficiency of this receptor and not an increased coupling of Ni protein to the adenylate cyclase. Thus, the postsynaptic interaction between the two receptors represents inter alia a sensitivity regulation of the two receptors. Evidence is also presented for the existence of a glucocorticoid regulation of NPY IR neurons, especially of those innervating the locus coeruleus, since after 2 weeks adrenalectomy reduced NPY IR in this area. Furthermore, glucocorticoid receptor IR was demonstrated in the nuclei of NPY nerve cell bodies of the nTS. Thus, glucocorticoids exert direct actions on cardiovascular NPY/CA costoring neurons, actions that may contribute to their hypertensive effects in humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Evidence for a cardiovascular role of central galanin neurons: focus on interactions with alpha 2-adrenergic and neuropeptide Y mechanisms.

By means of immunocytochemical analysis using the indirect immunofluorescence method, and by means of receptor autoradiography using 125I-galanin as a radioligand, further evidence has been obtained for the existence of pre- and postsynaptic features of galanin neurons in the nucleus tractus solitarius (nTS) and the dorsal motor nucleus of the vagus (dmnX) of the male rat. Thus, a high density of galanin immunoreactive nerve terminals was found within the medial subnucleus of the nTS, in the periventricular region and within the medial part of the dmnX. High densities of 125I-galanin binding sites were found in the entire medial and lateral part of the nTS and in the dmnX as evaluated at a level approximately 1-2 mm rostral to obex. The physiological studies were performed in alpha-chloralose anesthetized male rats by injecting galanin in the nmolar range i.c. and measuring mean arterial blood pressure and heart rate (HR). The results showed a weak hypotensive action of galanin (3 nmol) and a clearcut tachycardic action (10 nmol). When administered simultaneously with clonidine no additive effects were observed on mean arterial blood pressure but the bradycardic action of clonidine was blocked and the tachycardiac action of galanin prevailed. Similar results were obtained when galanin was injected simultaneously with NPY. These results indicate a cardiovascular role of galanin, and the morphological evidence favors the view that the galaninergic mechanism involved is located within the dorsal cardiovascular center of the medulla oblongata.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Nicotine-induced increases in brain luteinizing hormone releasing hormone-like immunoreactivity and in serum luteinizing hormone levels of the male rat.

By means of radioimmunoassay procedures luteinizing hormone releasing hormone (LHRH)-, Metenkephalin- and somatostatin-like immunoreactivities have been measured in discrete hypothalamic and preoptic nuclei as well as serum luteinizing hormone (LH) levels. Nicotine (2 mg/kg, i.p.) produced after 5 min a significant and selective increase in LHRH-like immunoreactivity in the median eminence and in the medial preoptic nucleus, associated with increases in serum LH levels but without any changes in Met-enkephalin and somatostatin-like immunoreactivities in the median eminence. The results indicate that the nicotine-induced activation of LHRH-immunoreactive neurons involves an enhanced processing of the precursor peptide to LHRH.

Animals↗