Clinical Neuroscience

[In memoriam Mariann Fodor]

MARCH 20, 2007

Clinical Neuroscience - 2007;60(03-04)

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Clinical Neuroscience

[Editor’s note]

RAJNA Péter

Clinical Neuroscience

[CHARACTERIZATION OF SPECIFIC SUCCINATE BINDING SITE IN BRAIN SYNAPTIC MEMBRANES]

MOLNÁR Tünde, KÚTINÉ Fekete Erzsébet, KARDOS Julianna, PALKOVITS Miklós

[A synaptic receptor for gamma-hydroxybutyric acid (GHB) - a naturally occuring metabolite of succinic acid1 - interacting succinate has been disclosed in rat and human nucleus accumbens (NA) subcellular fractions2, but the molecular properties of this recognition site were not characterised. To address the presumed recognition site for succinate, the pharmacological profile of [3H]succinate binding to synaptic membranes prepared from rat forebrain and human NA samples has been investigated. Specific [3H]succinate binding sites in the human NA synaptic membrane fraction showed a strong pH-dependence and were characterized by binding of succinate (IC50,SUCC=2.9±0.6 µM), GHB (IC50,GHB=2.1±1.3 µM) and gap junction blocker carbenoxolone (IC50,CBX=7.1±5.8 µM). A similar [3H]succinate binding profile was found in rat forebrain synaptic membrane fractions. We conclude the existence of a pHo-dependent synaptic membrane binding site for the intermediary metabolite succinate. The pharmacological properties of this recognition site may possibly suggest the existence of a hemichannel-like target protein for succinate.]

Clinical Neuroscience

[THE GHRELIN SYSTEM: PHYSIOPATHOLOGICAL INVOLVEMENT IN THE CONTROL OF BODY GROWTH AND ENERGY METABOLISM]

JACQUES Epelbaum

[This short review will summarize some recent findings on the physiopathology of the endogenous ghrelin/obestatin system by focussing on experimental studies aiming at blocking the effects of endogenous ghrelin and clinical studies investigating genotype/phenotype correlations concerning the genes encoding for ghrelin and its cognate receptor.]

Clinical Neuroscience

[SYNAPTIC CONNECTIONS OF GLUTAMATERGIC NERVE FIBRES IN THE RAT SUPRACHIASMATIC NUCLEUS]

KISS József, CSÁKI Ágnes, CSABA Zsolt, HALÁSZ Béla

[Background and purpose - The hypothalamic suprachiasmatic nucleus functioning as the principal circadian pacemaker in mammals, has a rich glutamatergic innervation. Nothing is known about the terminations of the glutamatergic fibres. The aim of the present investigations was to study the relationship between glutamatergic axon terminals and vasoactive intestinal polypeptide (VIP), GABA and arginine-vasopressin (AVP) neurons in the cell group. Methods - Double label immunocytochemistry was used and the brain sections were examined under the electron microscope. Vesicular glutamate transporter type 2 was applied as marker of the glutamatergic elements. Results - Glutamatergic fibers were detected in synaptic contact with GABAergic, VIP- and AVP-positive neurons forming asymmetric type of synapses. Conclusion - The findings are the first data on the synaptic contacts of glutamatergic axon terminals with neurochemically identified neurons in the suprachiasmatic nucleus.]

Clinical Neuroscience

[CENTRAL ATRIAL NATRIURETIC PEPTIDE IN DEHYDRATION]

UDO Bahner, HELMUT Geiger, PALKOVITS Miklós, LENKEI Zsolt, FRIEDRICH C. Luft, AUGUST Heidland

[To test the effect of dehydration on brain atrial natriuretic peptide (ANP) concentrations in areas important to salt appetite, water balance and cardiovascular regulation, we subjected rats to dehydration and rehydration and measured ANP concentration in 18 brain areas, as well as all relevant peripheral parameters. Water deprivation decreased body weight, blood pressure, urine volume, and plasma ANP, while it increased urine and plasma osmolality, angiotensin II, and vasopressin. ANP greatly increased in 17 and 18 brain areas (all cut cerebral cortex) by 24 h. Rehydration for 12 h corrected all changes evoked by dehydration, including elevated ANP levels in brain. We conclude that chronic dehydration results in increased ANP in brain areas important to salt appetite and water balance. These results support a role for ANP as a neuroregulatory substance that participates in salt and water balance.]

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[GLUTAMATERGIC PHENOTYPE OF HYPOTHALAMIC NEUROSECRETORY SYSTEMS: A NOVEL ASPECT OF CENTRAL NEUROENDOCRINE REGULATION]

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[While three decades ago, the co-existence of classical neurotransmitters and peptide neuromodulators in a single neuronal cell was considered to be rather exceptional, the phenomenon that neurons have a complex transmitter phenotype now appears to be the general rule. Parvicellular and magnocellular neurosecretory systems consist of neuronal cells which are specialized in secreting peptide neurohormones into the blood-stream to regulate hypophyseal functions. This mini-review, dedicated to the memory of Mariann Fodor, summarizes the current knowledge about the classical neurotransmitter content of different hypothalamic neurosecretory systems, with a special focus on the occurrence and putative functions of glutamate in parvicellular and magnocellular neurosecretory cells.]