Krister Eriksson

Increased brain histamine levels in Parkinson's disease but not in multiple system atrophy

We investigated histamine concentration in post‐mortem brain samples of patients with Parkinsons disease (PD, n = 24), multiple system atrophy (MSA, n = 8) and age‐matched controls (n = 27). Histamine concentrations were significantly increased in the putamen (to 159% of the control mean), substantia nigra pars compacta (to 201%), internal globus pallidus (to 234%) and external globus pallidus (to 200%), i.e. in areas which play a crucial role in the motor behaviour and which show typical functional alterations in PD. In MSA no significant differences were seen. Tele‐methylhistamine (histamine metabolite) concentrations were unchanged in PD. These results indicate that histamine concentration, but not its metabolism is increased in PD, but not in MSA. This finding may have implications in developing new drug therapies for PD and in differential diagnosis between PD and MSA.

Development of the histaminergic neurons and expression of histidine decarboxylase mRNA in the zebrafish brain in the absence of all peripheral histaminergic systems.

The histamine‐storing neural system in adult and developing zebrafish (Danio rerio) was studied with immunocytochemical and chromatographical methods. Furthermore, the gene for histidine decarboxylase was partially cloned and its expression mapped with in situ hybridization. The histamine‐storing neurons were only seen in the caudal hypothalamus, around the posterior recess of the diencephalic ventricle. Almost all parts of the brain, except the cerebellum, contained at least some histamine‐immunoreactive fibres. The ascending projections had the rostral part of the dorsal telencephalon as a major target. Descending projections terminated in the torus semicircularis, central grey and inferior olive. A prominent innervation of the optic tectum, which has not been reported in other fish, was seen. The in situ hybridization gave a strong signal in cells with the same anatomical position as the histamine‐immunoreactive neurons. The first histamine‐immunoreactive neurons appeared in the ventral hypothalamus at about 85 h post‐fertilization, and at 90 h, immunoreactive fibres terminated in the dorsal telencephalon. The embryonic histamine production described in mammals was lacking in this species. Both immunocytochemical and chromatographical studies indicated that histamine is absent in all other parts of the zebrafish body, and no specific hybridization was seen in any other part of the fish than the hypothalamus. The zebrafish could therefore be a very useful model for pharmacological in vivo studies of the histaminergic system of the brain, since the powerful peripheral actions of histamine should be lacking in this species.

Postnatal expression of H1-receptor mRNA in the rat brain: correlation to l-histidine decarboxylase expression and local upregulation in limbic seizures

Histamine is implicated in the regulation of brain functions through three distinct receptors. Endogenous histamine in the brain is derived from mast cells and neurons, but the importance of these two pools during early postnatal development is still unknown. The expression of histamine H1‐receptor in the rat brain was examined using in situ hybridization during postnatal development and in adults. For comparison, the expression of l‐histidine decarboxylase (HDC) in the two pools was revealed. H1‐receptor was evenly expressed throughout the brain on the first postnatal days, but resembled the adult, uneven pattern already on postnatal day 5 (P5). HDC was expressed in both mast cells and tuberomammillary neurons from birth until P5, after which the mast cell expression was no more detectable. In adult rat brain, high or moderate levels of H1‐receptor expression were found in the hippocampus, zona incerta, medial amygdaloid nucleus and reticular thalamic nucleus. In most areas of the adult brain the expression of H1‐receptor mRNA correlates well with binding data and histaminergic innervation. A notable exception is the hypothalamus, with high fibre density but moderate or low H1‐receptor expression. Systemic kainic acid administration induced increased expression of H1‐receptor mRNA in the caudate‐putamen and dentate gyrus, whereas no change was seen in the hippocampal subfields CA1–CA3 or in the entorhinal cortex 6 h after kainic acid injections. This significant increase supports the concept that histaminergic transmission, through H1‐receptor, is involved in the regulation of seizure activity in the brain.

Lack of Histamine Synthesis and Down-Regulation of H1 and H2 Receptor mRNA Levels by Dexamethasone in Cerebral Endothelial Cells

The purpose of this work was to determine whether cerebral endothelial cells have the capacity to synthesize histamine or to express mRNA of receptors that specifically respond to available free histamine. The histamine concentrations and the expression of L-histidine decarboxylase (HDC) and histamine H1 and H2 receptor mRNA, both in adult rat brain and in cultured immortalized RBE4 cerebral endothelial cells, were investigated. In this study endothelial cells were devoid of any kind of detectable histamine production, both in vivo and in the immortalized RBE4 cells in culture. Both the immunostainings for histamine and the in situ hybridizations for HDC were negative, as well as histamine determinations by HPLC, indicating that endothelial cells do not possess the capacity to produce histamine. Also, glucocorticoid (dexamethasone) treatment failed to induce histamine production in the cultured cells. Although the cerebral endothelial cells lack histamine production, a nonsaturable uptake in RBE4 cells is demonstrated. The internalized histamine is detected both in the cytoplasm and in the nucleus, which could indicate a role for histamine as an intracellular messenger. Histamine H1 and H2 receptor mRNA was expressed in RBE4 cells, and glucocorticoid treatment down-regulated the mRNA levels of both H1 and H2 receptors. This mechanism may be involved in glucocorticoid-mediated effects on cerebrovascular permeability and brain edema.

GABA in the nervous system of parasitic flatworms

In an immunocytochemical study, using an antiserum and a monoclonal antibody specific for the amino acid, gamma-aminobutyric acid (GABA), GABA-like immunoreactivity (GLIR) has been demonstrated for the first time in parasitic flatworms. In Moniezia expansa (Cestoda), GLIR was seen in nerve nets which were closely associated with the body wall musculature and in the longitudinal nerve cords. In the liver fluke Fasciola hepatica (Trematoda), the GLIR occurred in the longitudinal nerve cords and lateral nerves in the posterior half of the worm. GLIR was also detected in subtegumental fibres in F. hepatica. The presence of GABA was verified, using high-pressure liquid chromatography coupled with fluorescence detection. The concentration of GABA (mean +/- S.D.) in M. expansa anterior region was 124.8 +/- 15.3 picomole/mg wet weight, while in F. hepatica it was 16.8 +/- 4.9 picomole/mg. Since several insecticides and antinematodal drugs are thought to interfere with GABA-receptors, the findings indicate that GABAergic neurotransmission may be a potential target for chemotherapy in flatworms too.

Catecholamines demonstrated by glyoxylic-acid-induced fluorescence and HPLC in some microturbellarians

The microturbellarians Stenostomum leucops (Catenulida), Microstomum lineare (Macrostomida), Promonotus schultzei (Proseriata) and Gyratrix hermaphroditus (Rhabdocoela) were subjected to the glyoxylic-acid-induced-fluorescence method to reveal catecholaminergic parts of their nervous systems. Histofluorescence indicative of catecholamines was evident in nerve cells and fibers of all investigated species. The patterns of distribution were compared to those of other neuroactive substances. The catecholaminergic fluorescence was at least partly confined to separate neuronal subsets in S. leucops and M. lineare and probably also in P. schultzei. In S. leucops, the presence of dopa and dopamine was demonstrated by high-pressure liquid chromatography. The occurence of catecholamines in these representatives of four orders of microturbellarians suggests that catecholamines arose early in the evolution of flatworms and underscores the importance of dopaminergic substances for the function of early nervous systems.

Nitric oxide synthase in the pharynx of the planarian Dugesia tigrina

Abstract.The distribution of the nicotinamide adenine dinucleotide phosphate-(NADPH) diaphorase reaction, an indicator of nitric oxide synthase activity, was studied in the freshwater planarian Dugesia tigrina (Platyhelminthes). The reaction was restricted to the pharynx, where the inner epithelium was intensely stained and the outer epithelium moderately stained. Neurons that innervated the pharynx were also stained. The enzyme activity was studied by high pressure liquid chromatographic quantitation of the formed citrulline. The presumed nitric oxide synthase was dependent on NADPH, whereas no dependency on Ca2+ and calmodulin could be detected. Tetrahydrobiopterin increased the activity about fivefold to 218.2±24.9 fmol/mg protein per min. Nω-nitro-l-arginine depressed the enzyme activity by about 80%. The results indicate that nitric oxide has a role in the feeding behavior of planarians.

Glycine and GABAA receptor-mediated chloride fluxes in synaptoneurosomes from different parts of the rat brain

Strychnine-sensitive, inhibitory glycine receptors have not until lately been considered to play a significant role in neurotransmission in mammalian forebrain regions. In order to investigate the role of glycine as a neurotransmitter in brain we have measured glycine induced chloride fluxes in different adult rat forebrain areas using synaptoneurosomes and a chloride-sensitive fluorescent indicator. The results have been compared to those obtained with GABA. The synaptoneurosomes from every brain area investigated responded to both glycine and GABA with chloride fluxes in a picrotoxin sensitive manner. The effect of glycine was inhibited by strychnine, which had no effect on the GABA-induced Cl-flux. Bicuculline inhibited the effect of GABA, but had no effect on the glycine-induced Cl-flux. Addition of GABA did not affect the response to glycine and vice versa. The endogenous content of glycine and GABA in the synaptoneurosome preparations was about the same and synaptoneurosomes from every brain area investigated released both glycine and GABA upon depolarisation with KCl. The depolarisation induced release of both GABA and glycine was partly Ca(2+)-dependent and partly Ca(2+)-independent. These results indicate that glycine can induce inhibitory Cl- fluxes distinct from GABA induced fluxes in every investigated brain area and that glycine can be released upon depolarisation.

Localization and identification of catecholamines in the nervous system ofDiphyllobothrium dendriticum (Cestoda)

In the central and peripheral nervous system of larval and adultDiphyllobothrium dendriticum, catecholamines were detected using the glyoxylic acid-induced fluorescence method. High-pressure liquid chromatography (HPLC) analysis revealed the presence of dopa (about 65 ng/g fresh weight) and dopamine (5 ng/g fresh weight).

Green fluorescent protein as a tool for screening recombinant baculoviruses

The gene encoding the green fluorescent protein (GFP) from the jellyfish Aequorea victoria, ligated to the honeybee melittin signal peptide-encoding sequence, was inserted under transcriptional control of the polyhedrin promoter of the Autographa californica nuclear polyhedrosis virus and expressed in the Spodoptera frugiperda insect cell line Sf9 during viral infection. The recombinant green fluorescent protein was identified by SDS-PAGE gel electrophoresis followed by Coomassie blue staining of lysates from the recombinant baculovirus infected insect cells. Emission and excitation scanning of the recombinant baculovirus infected insect cells gave an emission maximum of 509 nm and excitation maximum of 398 nm. The GFP protein expressed was also detected in infected insect cells by a flow cytometer analysis.