G. Falkay

Analysis of the role of central and peripheral α2-adrenoceptor subtypes in gastric mucosal defense in the rat

The present study confirmed our previous assumption on the crucial role of central alpha2B-like adrenoceptor subtype in gastric mucosal defense. It was found that beside clonidine, rilmenidine, an alpha2/imidazoline receptor agonist and ST-91, an alpha2B-adrenoceptor preferring agonist inhibited the mucosal lesions induced by ethanol given intracerebroventricularly (i.c.v.). The ED50 values for clonidine, rilmenidine and ST-91 are 0.2, 0.01 and 16 nmol/rat i.c.v., respectively. The effect was reversed by the intracerebroventricularly injected alpha2B/2C-adrenoceptor antagonists prazosin and ARC-239, indicating the potential involvement of central alpha2B/2C-adrenoceptor subtype in the protective action. The gastroprotective effect of adrenoceptor stimulants was reversed by bilateral cervical vagotomy, suggesting that vagal nerve is likely to convey the central action to the periphery. In gastric mucosa both nitric oxide and prostaglandins may mediate the centrally-induced effect, since both indomethacin and N(G)-nitro-L-arginine reversed the protective effect of alpha2-adrenergic stimulants. Though expression of mRNA of alpha2B-, as well as alpha2A- and alpha2C-adrenoceptor subtypes was demonstrated in gastric mucosa of the rat, the hydrophilic ST-91, given peripherally (orally, subcutaneously), failed to exert mucosal protection, in contrast with clonidine and rilmenidine which were also effective. Consequently, while peripheral alpha2B-adrenoceptors are not likely to be involved in gastric mucosal protection, activation of central alpha2B-like adrenoceptor subtype may initiate a chain of events, which result in a vagal dependent gastroprotective action.

Peripheral oxytocin treatment modulates central dopamine transmission in the mouse limbic structures

The effects of subcutaneous (s.c.) oxytocin treatment have been investigated on various parameters of dopaminergic neurotransmission in basal forebrain structures (nucleus olfactorius posterior + nucleus accumbens + septum) of the mouse. Acute oxytocin treatment failed to influence dopamine utilization in the basal forebrain. Following chronic injections of oxytocin (0.2 mg/kg) for 8 8 days, the neuropeptide decreased dopamine utilization. Neither in vivo nor in vitro oxytocin treatment was capable of influencing the in vitro uptake of [(3)H]dopamine in basal forebrain slices. The spontaneous release of [(3)H]dopamine (in the presence of 4.2 mM K(+)) from basal forebrain tissue slices was not affected by in vitro or acute or chronic in vivo oxytocin treatment. The stimulated release of [(3)H]dopamine (in the presence of 30 mM K(+)) was significantly inhibited by chronic in vivo oxytocin administration. Chronic oxytocin treatment decreased the B(max) value of [(3)H]spiroperidol binding in the basal forebrain. The dissociation constant (K(d)) of [(3)H]spiroperidol binding was not influenced by oxytocin. The data indicate that peripheral oxytocin treatment is capable of modifying dopaminergic neurotransmission in mouse basal forebrain regions.

Characterization of late-pregnant rat uterine contraction via the contractility ratio in vitro Significance of α1-adrenoceptors

The aim of this study was to characterize the ability of late-pregnant (days 15-22) rat uterine tissue rings to contract in response to electric field stimulation in vitro. For this purpose, maximum rhythmic contractions were elicited by optimum choice of the period time and the pulse width, the two main parameters of electric field stimulation. In parallel, the plasma 17beta-estradiol and progesterone levels were determined. It was found that the contractility ratio, i.e. the quotient of the optimum pulse width and the period time, is a good parameter with which to express the contractility. The larger the contractility ratio, the better the ability to contract. Evaluation of the area under the curve did not furnish information relating to the contractility in this method. A very close correlation was observed between the contractility ratio and the quotient of the 17beta-estradiol and progesterone levels on different days, demonstrating that the in vitro ability characterized by the contractility ratio is in keeping with the physiological regularity. There was also a very close correlation between the contractility ratio and the quotient of the alpha1- and beta-adrenergic receptors, suggesting the main role of the numbers of alpha1-receptor in pregnant uterine contractility. It is believed that this is the first in vitro model to give a numerical measure concerning the ontogeny of uterine contractility in late pregnancy.

An intraperitoneally administered pentapeptide protects against Aβ1-42 induced neuronal excitation in vivo

The underlying cause of Alzheimers disease (AD) is thought to be the accumulation and aggregation of a misfolded protein, amyloid-beta (Abeta). A promising strategy against AD is the application of protective, peptide-based neuroprotective agents that selectively bind to Abeta. We recently described a pentapeptide, LPYFDa, which recognizes Abeta (1-42) and protects neurons against the toxic effects of aggregated Abeta (1-42) both in vitro and in vivo. Our previous work indicated that the in vivo ejection of fibrillar Abeta (1-42) into the hippocampal CA1 region resulted in a massive increase in the NMDA-evoked neuronal firing rate. Our current aim was to study whether intraperitoneally administered LPYFDa is capable of protecting against the synaptotoxic action of fibrillar Abeta (1-42) administered by iontophoresis. Our investigations of the in vivo biodistribution of tritium-labelled LPYFDa and single-unit electrophysiology revealed that LPYFDa readily crosses the blood-brain barrier, and protects the synapses against the excitatory action of fibrillar Abeta (1-42) in a relatively wide temporal window in rat. This pentapeptide may serve as a lead compound for the design of novel drug candidates for the prevention of AD.

Fermented Wheat Germ Extract (Avemar) Inhibits Adjuvant Arthritis

Abstract:  Anti‐inflammatory efficacy of the fermented wheat germ extract (FWGE, Avemar) in the rat adjuvant arthritis (AA) model was examined. To Wistar rats with AA, different doses of FWGE and anti‐inflammatory drugs (indomethacin, dexamethasone) as monotherapies were administered and FWGE and either diclofenac or dexamethasone were also given in combination. Besides plethysmographies of the paws, histological investigations of synovial tissues were also performed along with detection of CD4+ and CD8+ T lymphocytes. Gene expressions of COX‐1 and 2 were determined by real‐time polymerase chain reaction (PCR). FWGE monotherapy significantly inhibited the development of the secondary (immune‐mediated) response in AA, and dexamethasone and indomethacin exerted inhibitory effects in a degree comparable to that of FWGE. Histological analysis of the affected joints confirmed the results. FWGE inhibited COX‐1 and ‐2, while indomethacin enhanced COX‐2 gene expressions. FWGE had an additive interaction with diclofenac. It is concluded that FWGE has significant anti‐inflammatory efficacy confirmed by plethysmography, histology, and real‐time PCR.

3D QSAR models for α2a-adrenoceptor agonists

Abstract Three-dimensional structure–activity relationship studies of α 2a -adrenoceptor agonists were carried out by Distance Comparison (DISCOthech) and Comparative Molecular Field Analysis (CoMFA) methods to define the pharmacophore and a quantitative model, respectively, of this class of compounds. The statistical validation of the CoMFA model indicates its high predictive performance for binding affinities of new α 2a -adrenoceptor agonists.

Effects of streptozotocin-induced diabetes on the uterine adrenergic nerve function in pregnant rats: A superfusion study

Pregnancy-induced diabetes mellitus poses one of the greatest challenges in obstetrical practice. The direct action of diabetes on the myometrial adrenergic functions has not been completely characterized. Accordingly, the present study relates to the impact of experimentally induced diabetes on the presynaptic functions of the rat uterus in relation to gestational age. Experiments were carried out on non-pregnant, early-pregnant (day 7), middle-pregnant (day 14) and late-pregnant (day 21) animals. Diabetes was induced with streptozotocin (60 mg/kg, i.v.) in virgin female or early-pregnant animals (on day 2 for the day 7 experiments and on day 5 for the experiments on the middle and late-pregnant animals). Myometrial samples were utilized for superfusion experiments. After saturation, [3H]noradrenaline perfusate fractions were collected and electric field stimulation was applied to determine the amount of transmitter liberated. Additionally, the total uptake capacity of each sample was assayed. Experimental diabetes decreases the transmitter uptake capacity both in virgin rats and at all stages of pregnancy. In early pregnancy (on day 7), this limitation in uptake is obvious as early as 5 days after the induction of diabetes. In non-pregnant animals, the electrically stimulated transmitter release is inhibited substantially, a similar decrease being observed only at mid-pregnancy (day 14). The present superfusion study proves that experimental diabetes depresses the presynaptic adrenergic functions (both the transmitter uptake and the stimulated release) in the myometrium of the rat. Since the effect of diabetes on the uptake capacity can be detected earlier than for generally accepted markers of peripheral neuropathies, superfusion can be suggested as a sensitive and reliable approach for investigations of hyperglycaemia-related functional deteriorations. We speculate that diabetes-induced functional deterioration of the adrenergic nerves could partially explain the anomalies of the reproductive functions found in diabetic patients if a similar mechanism is operative in humans.

Long-term pretreatment with desethylamiodarone (DEA) or amiodarone (AMIO) protects against coronary artery occlusion induced ventricular arrhythmias in conscious rats

The aim of this investigation was to compare the effectiveness of long-term pretreatment with amiodarone (AMIO) and its active metabolite desethylamiodarone (DEA) on arrhythmias induced by acute myocardial infarction in rats. Acute myocardial infarction was induced in conscious, male, Sprague-Dawley rats by pulling a previously inserted loose silk loop around the left main coronary artery. Long-term oral pretreatment with AMIO (30 or 100 mg·(kg body mass)(-1)·day(-1), loading dose 100 or 300 mg·kg(-1) for 3 days) or DEA (15 or 50 mg·kg(-1)·day(-1), loading dose 100 or 300 mg·kg(-1) for 3 days), was applied for 1 month before the coronary artery occlusion. Chronic oral treatment with DEA (50 mg·kg(-1)·day(-1)) resulted in a similar myocardial DEA concentration as chronic AMIO treatment (100 mg·kg(-1)·day(-1)) in rats (7.4 ± 0.7 μg·g(-1) and 8.9 ± 2.2 μg·g(-1)). Both pretreatments in the larger doses significantly improved the survival rate during the acute phase of experimental myocardial infarction (82% and 64% by AMIO and DEA, respectively, vs. 31% in controls). Our results demonstrate that chronic oral treatment with DEA resulted in similar cardiac tissue levels to that of chronic AMIO treatment, and offered an equivalent degree of antiarrhythmic effect against acute coronary artery ligation induced ventricular arrhythmias in conscious rats.

ATP-sensitive potassium channels modulate in vitro tocolytic effects of β₂-adrenergic receptor agonists on uterine muscle rings in rats in early but not in late pregnancy.

Aim To investigate whether ATP-sensitive potassium (KATP) channels modulate the tocolytic effect of β2-AR agonists (ritodrine and salmeterol) in early-pregnant (day 6) and late-pregnant (day 22) rat uterus in vitro, in order to examine the relation between the KATP channel sulphonylurea-binding regulatory subunit (SUR) expression and pharmacological reactivity of β2-AR agonists. Methods The tocolytic effects of ritodrine and salmeterol (10-10-10-5 M) on spontaneous rhythmic contractions were investigated cumulatively, alone, or in the presence of the KATP channel blocker glibenclamide (10-6 M) and the KATP channel opener pinacidil (10-9-10-7 M) after 5-min preincubation. Results β2-AR agonist induced myometrial relaxation was inhibited by glibenclamide and enhanced by pinacidil on day 6, when SUR1 expression levels were high. Neither glibenclamide nor pinacidil mediated tocolytic effect was measured on day 22. Conclusion Low expression of the KATP channels at the end of gestation may facilitate enhanced excitability and contractility in the rat myometrium. The combination of a betamimetic and a KATP channel opener will therefore not be of therapeutic relevance in the treatment of preterm delivery.

Effects of newly synthetized isoquinoline derivatives on rat uterine contractility and ROCK II activity

Protein kinases have an important role in signal transduction in the cellular system via protein phosphorylation. RhoA activated Rho-kinases have a pivotal role in the regulation of smooth muscle contraction. ROCK I and ROCK II phosphorylate myosin-phosphatase and myosin-kinase, which induces contraction in the myometrium. Several studies have investigated the affinity of isoquinoline alkaloids (HA-1077, H1152P) to Rho-kinases, and these compounds notably inhibited the Ca2+-independent process. We measured the efficiency of 25 original, newly synthesized isoquinoline derivatives for the Rho-kinase activity using Rho-associated kinase activity assay and determined their effects on the non-pregnant, 20-day pregnant and parturient rat myometrial contraction in vitro. The IC50 values of 11 from among the 25 derivatives were significantly lower on the oxytocin-induced non-pregnant rat uterine contraction compared with Y-27632 and fasudil, although their maximal inhibitory effects were weaker than those of Y-27632 and fasudil. We measured the effects of 11 isoquinoline molecules with significant IC50 values on ROCK II activity. We found two isoquinolines out of 11 compounds (218 and 852) which decreased the active ROCK II level similarly as Y-27632. Then we found that 218 and 852 relaxed the 20th-day pregnant and parturient rat uterus with greater potency as compared with fasudil. The majority of the synthesized isoquinoline derivatives have uterus relaxant effects and two of them significantly suppress the Rho-kinase mediated myosin light chain phosphorylation. Our results may suggest that the isoquinoline structure has a promising prospect for the development of new and effective inhibitors of uterine contractions in preterm birth.