Andor H. Molnár

Reduction of experimental colitis in the rat by inhibitors of glycogen synthase kinase‐3β

The effects of the inhibitors of glycogen synthase kinase‐3β (GSK‐3β), TDZD‐8 and SB 415286, which can substantially reduce the systemic inflammation associated with endotoxic shock in vivo, have now been investigated on the acute colitis provoked by trinitrobenzene sulphonic acid (TNBS) in the rat. Administration of the GSK‐3β inhibitor TDZD‐8 (0.1, 0.33 or 1.0 mg kg−1, s.c., b.i.d., for 3 days) caused a dose‐dependent reduction in the colonic inflammation induced by intracolonic TNBS assessed after 3 days, both as the area of macroscopic involvement and as a score using 0–10 scale. Likewise, following administration of the GSK‐3β inhibitor SB 415286 (0.1, 0.33 or 1.0 mg kg−1, s.c., b.i.d., for 3 days), the extent and degree of the TNBS‐provoked colonic inflammation was reduced. Administration of either TDZD‐8 or SB 415286 reduced the fall in body weight following challenge with TNBS at each dose level studied. The increase in myeloperoxidase activity, an index of neutrophil infiltration into the TNBS‐induced inflamed colon, was significantly inhibited by both TDZD‐8 and SB 415286 at each dose level. The increase in the levels of the proinflammatory cytokine, TNF‐α, in the inflamed colon was also significantly inhibited by either compound at the highest doses evaluated. The elevated levels of the transcription factor NF‐κB subunit p65, as determined by Western blot in the nuclear extracts from the TNBS‐provoked inflamed colonic tissue, were dose‐dependently reduced by TDZD‐8 or SB 415286 treatment. These findings demonstrate that two chemically distinct selective inhibitors of the activity of GSK‐3β reduce the inflammation and tissue injury in a rat model of acute colitis. The mechanisms underlying this anti‐inflammatory action may be related to downregulation of NF‐κB activity, involved in the generation of proinflammatory mediators.

Histamine-induced enhancement of vasopressin and oxytocin secretion in rat neurohypophyseal tissue cultures

The effects of histamine (HA) on vasopressin (VP) and oxytocin (OT) secretion were studied in 13-14-day cultures of isolated rat neurohypophyseal (NH) tissue. The VP and OT contents of the supernatant were determined by radioimmunoassay (RIA) after a 1 or 2-h incubation. Significantly increased levels of VP and OT production were detected in the tissue culture media following HA administration, depending on the HA dose. The elevation of NH hormone secretion could be partially blocked by previous administration of the HA antagonist mepyramine (MEP, an H1 receptor antagonist) or cimetidine (CIM, an H2 receptor antagonist). Thioperamide (TPE, an H3-H4 receptor antagonist) did not influence the VP or OT secretion increase induced by HA. The application of MEP, CIM or TPE after HA administration proved ineffective. The H1 and H2 receptors are mainly involved in the HA-induced increase of both VP and OT secretion in isolated NH tissue cultures. The results indicate that NH hormone release is influenced directly by the histaminergic system, and the histaminergic control of VP and OT secretion from the NH tissue in rats can occur at the level of the posterior pituitary.

Kynurenine aminotransferase in the supratentorial dura mater of the rat: Effect of stimulation of the trigeminal ganglion

Electrical stimulation of the trigeminal ganglion has been widely used as a model of nociception, characterizing migraine. This treatment is known to evoke release of neuropeptides and neurotransmitters from nerve fibers of the dura mater. On the basis of immunocytochemical investigations, we found that under normal conditions, surface membranes of Schwann cells surrounding nerve fibers in the supratentorial dura mater display kynurenine aminotransferase-immunoreaction (KAT-IR); also KAT-IR are the granules of mast cells and the cytoplasms of macrophages (histiocytes). In consequence of stimulation of the trigeminal ganglion, Schwann cells in the dura mater became conspicuously swollen while their KAT-IR decreased considerably; also KAT-IR of mast cells and macrophages decreased significantly. At the same time, nitric oxide synthase (NOS)-IR of nerve fibers in the dura mater increased, suggesting release of nitric oxide (NO), this is known to be involved in NMDA receptor activation leading to vasodilation followed by neurogenic inflammation. Because kynurenic acid (KYNA) is an antagonist of NMDA receptors, we hypothesize that KYNA and its synthesizing enzyme, KAT, may play a role in the prevention of migraine attacks.

Inhibitory effect of vasopressin receptor antagonist OPC-31260 on experimental brain oedema induced by global cerebral ischaemia

SummaryThe effects of the non-peptide vasopressin V2 receptor antagonist 5-dimethylamino-1-[4-(2-methylbenzoylamino)benzoyl]-2,3,4,5-tetrahydro-1H-benzazepine hydrochloride (OPC-31260) on the cerebral oedema induced by general cerebral hypoxia were studied in rats. The general cerebral hypoxia was produced by bilateral common carotid ligation in Sprague-Dawley rats of the CFY strain. By 6 h after the ligation, half of the rats had died, but the survival rate was significantly higher following OPC-31260 administration. Electron microscopic examinations revealed typical ischaemic changes after the carotid ligation. The carotid ligation increased the brain contents of water and Na+ and enhanced the plasma vasopressin level. The increased brain water and Na+ accumulation was prevented by OPC-31260 administration, but the plasma vasopressin level was further enhanced by OPC-31260. These results demonstrate the important role of vasopressin in the development of the disturbances in brain water and electrolyte balance in response to general cerebral hypoxia. The carotid ligation-induced cerebral oedema was significantly reduced following oral OPC-31260 administration. The protective mechanism exerted by OPC-31260 stems from its influence on the renal vasopressin V2 receptors. These observations might suggest an effective approach to the treatment of global hypoxia-induced cerebral oedema in humans.

Effects of galanin–monoaminergic interactions on vasopressin secretion in rat neurohypophyseal cell cultures

The effects of dopamine (DA), serotonin (5-HT), histamine (HA), adrenaline (ADR), noradrenaline (NADR) and K(+) administration on vasopressin (VP) secretion were studied in 13-14-day cultures of rat neurohypophyseal (NH) cells, and it was examined whether galanin (GAL) can modify the VP release enhancement induced by these monoaminergic compounds. An enzymatic dissociation technique was used to make the rat NH cell cultures. The VP contents of the supernatants of 14-day cultures were determined by radioimmunoassay. Following the administration of 10(-6) M GAL, the VP secretion into the supernatant media decreased. DA, 5-HT, ADR or NADR treatment increased the VP level substantially, while the enhancing effect of HA was more moderate. GAL administration before DA, ADR and NADR treatment prevented the VP concentration increase induced by DA, ADR or NADR. Preincubation with GAL reduced the 5-HT- or HA-induced VP level increases; the VP concentrations of the supernatant media remained above the control level. The GAL blocking effect was prevented by previous treatment with the GAL receptor antagonist galantid (M15). GAL had no effect on the VP level increase induced by K(+), which causes a non-specific hormone secretion. The results indicate that the changes in VP secretion induced by the monoaminergic system can be directly influenced by the GAL-ergic system. The interactions between the monoaminergic and GAL-ergic systems regarding VP secretion occur at the level of the posterior pituitary.

Effects of orexin-monoaminergic interactions on oxytocin secretion in rat neurohypophyseal cell cultures ☆

The effects of orexin-monoaminergic compound interactions on oxytocin release were studied in 14-day rat neurohypophyseal cell cultures prepared by an enzymatic dissociation technique. The oxytocin contents of the supernatants were determined by radioimmunoassay. Following the administration of orexin-A or orexin-B in increasing doses, significant changes were not observed in the oxytocin content of the supernatant media. The oxytocin level increased substantially in response to adrenaline, noradrenaline, serotonin, histamine, dopamine or K(+) treatment. Preincubation with orexin-A or orexin-B reduced the adrenaline-, histamine- or serotonin-induced oxytocin level increases, but the oxytocin concentrations of the supernatant media remained above the control level. There was no significant difference in decreasing effect between orexin-A and orexin-B. Neither orexin-A nor orexin-B induced changes in oxytocin release following monoaminergic compound treatment. The results indicate that the changes in oxytocin secretion induced by the monoaminergic system can be directly influenced by the orexin system. The effects of orexin on oxytocin release can be antagonized by an orexin-1 receptor-specific antagonist. It may be presumed that the orexins can play a role in the pathogenetic process of metabolic diseases (e.g. obesity) by reducing the effects of increased oxytocin release caused by monoaminergic compounds. The interactions between the monoaminergic and orexin systems regarding oxytocin secretion occur at both the hypothalamic and the neurohypophyseal levels.

Inhibitory effect of galanin on adrenaline- and noradrenaline-induced increased oxytocin secretion in rat neurohypophyseal cell cultures.

The effects of the interactions between the 29 amino acid-containing peptide galanin and adrenaline or noradrenaline on the secretion of oxytocin were studied in 13- to 14-day cultures of isolated rat neurohypophyseal tissue. The α-receptor antagonist corynanthine blocked the adrenaline-induced increase of oxytocin secretion. When the β-receptor antagonist propranolol was added before the noradrenaline treatment, the antagonist prevented the noradrenaline-induced enhancement of oxytocin release. Following the addition of galanin, the extent of oxytocin secretion into the supernatant medium decreased. Adrenaline and noradrenaline treatments increased the oxytocin level. Preincubation with galanin reduced the adrenaline- and noradrenaline-induced oxytocin level elevations. The blocking effect of galanin was prevented by previous treatment with the galanin receptor antagonist galantid (M15). When adrenaline or noradrenaline treatment was applied before galanin addition, the oxytocin secretion remained enhanced. The present results indicate that the changes in oxytocin secretion induced by the adrenergic system can be directly influenced by the galaninergic system. The interactions between the adrenergic and galaninergic systems from the aspect of oxytocin secretion can occur at the level of the posterior pituitary, independently of the hypothalamus.

Biological half-life and organ distribution of [3H]8-arginine vasopressin following administration of vasopressin receptor antagonist OPC-31260.

The effects of the antidiuretic (V(2)) non-peptide receptor antagonist OPC-31260 on the plasma vasopressin level and the biological half-life and organ distribution of radiochemically pure, biologically active [(3)H]8-arginine vasopressin [spec. act.: 15.9 mCi/mmol (588 GBq/mmol)] were studied in Wistar rats. The plasma vasopressin level increased significantly throughout the whole experimental period (24 h). There was no change in the fast phase of the curves of total radioactivity disappearance from the plasma after the administration of [(3)H]arginine vasopressin (control: 1.51+/-0.17 min, OPC-31260-treated: 1.42+/-0.12 min, n=10). The fast phase of the disappearance curves of intact [(3)H]arginine vasopressin did not change either following the administration of OPC-31260 in a dose of 30 mg/kg p.o. (control: 1.06+/-0.19 min, OPC-31260-treated: 1.00+/-0.15 min, n=6). The slow phase of the biological half-life, which is characteristic for the examined compound, proved to be significantly longer (total radioactivity control: 9.29+/-0.61 min, OPC-31260-treated: 12.33+/-0.42 min, P<0.05, n=10; [(3)H]arginine vasopressin radioactivity: control: 5.96+/-0.58 min, OPC-31260-treated: 8.90+/-0.37 min, P<0.05, n=6). In the control rats, the radioactivity was accumulated to the greatest extent in the neurohypophysis, adenohypophysis and kidney. Following OPC-31260 administration, significantly more radioactive compounds accumulated in the kidney (control: 0.30+/-0.052 total radioactivity %/100 mg organ weight, OPC-31260-treated: 0.50+/-0.133 total radioactivity %/100 mg organ weight, P<0.05, n=10) and neurohypophysis (control: 0.37+/-0.053 total radioactivity %/100 mg organ weight, OPC-31260-treated: 0.52+/-0.076 total radioactivity %/100 mg organ weight, P<0.05, n=10). Our results permit the conclusion that the antidiuretic antagonist OPC-31260 not only blocks the V(2) receptors, but also increases the biological half-life of vasopressin. The longer biological half-life of vasopressin following OPC-31260 administration may play a role in the elevation of the plasma vasopressin level.

The effects of orexins on monoaminerg-induced changes in vasopressin level in rat neurohypophyseal cell cultures

The effects of orexin-monoaminergic compound interactions on vasopressin release were studied in 14-day neurohypophyseal cell cultures from adult rats, prepared by an enzymatic dissociation technique. The vasopressin contents of the supernatants were determined by radioimmunoassay. Following administration of either orexin-A or orexin-B in increasing doses, significant changes were not observed in the vasopressin levels of the supernatant media. The vasopressin level substantially increased after epinephrine, norepinephrine, serotonin, histamine, dopamine or K(+) treatment. Preincubation with either orexin-A or orexin-B reduced the epinephrine-, histamine- or serotonin-induced increases in vasopressin level, but the vasopressin concentrations of the supernatant media remained above the control level. There was no significant difference in decreasing effect between orexin-A and orexin-B. Neither orexin-A nor orexin-B induced changes in vasopressin release following monoaminergic compound treatment. The results indicate that the changes in vasopressin secretion induced by the monoaminergic system can be directly influenced by orexin system. It may be presumed that the orexins can play a physiological role in the regulation of the water metabolism by reducing the effect of increased vasopressin release caused by monoaminergic compounds. The interactions between the monoaminergic and orexin systems regarding vasopressin secretion occur at both the hypothalamic and the neurohypophyseal level.

Reliability of anthropometric parameters in the prediction of the visceral fat area among adult women.

Visceral fat accumulation is a risk factor for cardiometabolic diseases. Magnetic resonance imaging (MRI) and computed tomography (CT) provided the most accurate techniques of abdominal fat assessment, but these methods are very expensive. The aim of this study was to examine and compare the predictive ability of simple anthropometric parameters for visceral fat area (VFA) among adult women in different age and obesity status groups. The sample consisted of 133 adult women (aged 18-76 years). All subjects underwent anthropometric measurements. Body composition and VFA were determined with a multi-frequency bioimpedance analyzer (BIA). 16.9% of the younger women (age < 45) were obese with a body-mass index (BMI) > or = 30.0 kg/m2, and 23.2% of the older individuals (age > 45) had BMI > or = 30 kg/m2. After age and BMI adjustment, the best correlation was observed between VFA and waist circumference (WC) in younger women (R = 0.347, p = 0.002). In the case of the older women, the best correlation efficient values were for SAD (R = 0.560, p < 0.001) and hip circumference (R = 0.550, p < 0.001). The partial correlation coefficients were consistently higher for younger subjects with excessive fat accumulation (overweight & obese subgroup; individuals with WC > 80 cm) compared to women without obesity. Results of the multiple linear stepwise regression analyses showed the significance of age and BMI in prediction of VFA. In addition, hip circumference (HC) was one of the methods that best reflected VFA in older women independently from obesity status. Using single anthropometric parameters is not usually sufficient for predicting with good accuracy the VFA, but the convenient combination of these parameters could be a suitable way for the reliable prediction in Hungarian women.