Vasorelaxant effects of forsythide isolated from the leaves of Forsythia viridissima on NE-induced aortal contraction.

Forsythide (F1) isolated from the leaves of Forsythia viridissima (Oleaceae) showed vasorelaxant effects on norepinephrine (NE)-induced contraction of rat aorta with or without endothelium. This compound did not affect contraction induced by high concentration potassium (60 mM K(+)) and phorbol 12,13-diacetate, but inhibited NE-induced contraction in the presence of nicardipine. These results demonstrated the inhibitory effects of F1 on NE-induced vasocontraction presumably due to decrease of calcium influx from extracellular area, which was induced by NE.

Blockade of D2 dopamine receptors in the VTA induces a long-lasting enhancement of the locomotor activating effects of amphetamine.

The present study examined the effects of pre-exposure to eticlopride, a D2 dopamine receptor antagonist, in the ventral tegmental area (VTA) on the subsequent locomotor activating effects of amphetamine (AMPH). Rats were pre-exposed to one of three doses of eticlopride (0.75, 3.0 or 12.0 microg/0.5 microl per side) or saline (0.5 microl/side) in the VTA, once every third day, for a total of three infusions. Locomotor activity was recorded for 2 h following each pre-exposure injection. The low and intermediate doses of eticlopride produced no effects, while the high dose decreased locomotor activity compared to saline controls. 10-14 days following the last pre-exposure injection, all rats were challenged with AMPH (1.0 mg/kg, ip) and locomotor activity was recorded. Rats pre-exposed to the low dose of eticlopride exhibited enhanced locomotor activity whereas those pre-exposed to the intermediate or high doses did not differ from saline pre-exposed controls, suggesting that blockade of D2 dopamine receptors in the VTA can lead to sensitized locomotor responding to AMPH. To investigate the possible mechanism by which the low dose of eticlopride induced sensitization, extracellular levels of dopamine were measured as increasing concentrations of eticlopride (0.1, 1.0, 10.0 and 100.0 micromol/l) were perfused through a microdialysis probe implanted in the VTA. Only the lowest eticlopride concentration elevated extracellular dopamine levels. Therefore, as in the case of AMPH-induced sensitization, the induction by eticlopride of sensitization to AMPH may be initiated by the ability of eticlopride to increase extracellular levels of dopamine in the VTA.

Previous exposure to VTA amphetamine enhances cocaine self-administration under a progressive ratio schedule in a D1 dopamine receptor dependent manner.

The effect of previous exposure to amphetamine (AMPH) in the ventral tegmental area (VTA) on the subsequent self-administration of cocaine was assessed. Rats in different groups were pre-exposed to three injections into the VTA of either saline (0.5 microl/side) or AMPH (2.5 microg/0.5 microl/side). Injections were given once every third day. Starting 7-10 days after the last pre-exposure injection, rats were trained to self-administer cocaine (0.3 mg/kg/infusion) under fixed ratio 1 and 2 (FR1 and FR2) schedules and then tested under a progressive ratio (PR) schedule of reinforcement for six consecutive days. No differences between groups were observed during self-administration training under the FR schedules of reinforcement. However, when tested under the PR schedule, VTA AMPH pre-exposed rats worked more and, as a result, obtained more infusions of cocaine than saline pre-exposed rats. Rats in a separate group pre-exposed to VTA AMPH but co-infused with the D(1)-like dopamine (DA) receptor antagonist SCH23390 (0.25 microg/0.5 microl/side) did not show enhanced cocaine self-administration. These rats, as well as others pre-exposed to VTA SCH23390 alone showed levels of cocaine self-administration similar to saline pre-exposed rats. Thus, in a manner paralleling the sensitization of AMPH-induced locomotion and nucleus accumbens DA overflow, previous exposure to AMPH in the VTA leads to enhanced intravenous self-administration of cocaine and activation of D(1) DA receptors in this site during pre-exposure is necessary for the production of this effect.

Locomotor response to novelty predicts a rat's propensity to self-administer nicotine.

RATIONALE: A positive correlation between responding to novelty and propensity to subsequently self-administer a drug has been reported for opioids and psychomotor stimulants but remains to be investigated for nicotine. OBJECTIVE: The possibility that locomotor responding to novelty can predict a rat's propensity to self-administer nicotine was therefore assessed. METHODS: Rats' locomotor response to a novel environment was assessed, and animals were subsequently tested for their self-administration of nicotine. RESULTS: Significant positive correlations were obtained between responding to novelty and acquisition of nicotine self-administration over 12 days of testing under fixed-ratio schedules as well as subsequent responding for the drug under a progressive-ratio (PR) schedule of reinforcement. When designated as high (HR) or low (LR) responders based on whether their locomotor responses on the novelty screen were above or below the median activity level of the subject sample, HR animals, compared with LR rats, acquired nicotine self-administration more readily and worked more to obtain the drug when tested under the PR schedule. CONCLUSION: These findings are consistent with those obtained with other drugs and suggest that locomotor responding to a novel environment can be used to predict a rat's propensity to self-administer nicotine.

Nitric oxide donor FK409 and 8-bromoguanosine-cyclic monophosphate attenuate cardiac contractility assessed by Emax.

FK409 decomposes and releases nitric oxide (NO) spontaneously when it is dissolved in phosphate buffer solution at 37 degrees C. With the use of this NO donor, the effect of exogenous NO on cardiac contractility was examined by assessing Emax. alpha-chloralose-anaesthetized dogs were instrumented for measurements of left ventricular (LV) pressure and volume and coronary blood flow (CBF) in the left anterior descending artery (LAD). FK409, 8-bromoguanosine-cyclic-monophosphate (8-Br-cGMP) and papaverine were infused into the LAD, and Emax was determined by transient inferior vena cava occlusion when CBF was increased and reached its peak. Neither drug affected heart rate nor LV pressure just before the measurement of Emax. FK409 increased CBF and decreased Emax in a dose-dependent manner. 8-Br-cGMP also increased CBF and decreased Emax in a dose-dependent manner. Pretreating with propranolol did not affect the effects of FK4098-Br-cGMP on CBF and Emax. Papaverine increased mean CBF but did not affect Emax. In conclusion NO attenuates cardiac contractility in vivo, while increasing CBF. This effect seems to be mediated by cyclic-guanosine monophosphate, a second messenger of NO.

Intramyocardial delivery of basic fibroblast growth factor-impregnated gelatin hydrogel microspheres enhances collateral circulation to infarcted canine myocardium.

The present study examined whether basic fibroblast growth factor (bFGF)-impregnated acidic gelatin hydrogel microspheres (AGHM) would enhance collateral development to the infarct area in dogs with coronary occlusion. Studies were conducted in 28 dogs with a 2-week occlusion of the proximal left anterior descending coronary artery (LAD). The dogs were divided into 3 groups according to treatment: Group A treated with bFGF-impregnated AGHM in the infarct area; Group B with free-form bFGF; Group C with AGHM alone. Coronary angiography (n=15; Group A, 7 dogs; Group B, 5 dogs; Group C, 3 dogs) and a regional myocardial blood flow study (n=13; Group A, 6 dogs; Group B, 4 dogs; Group C, 3 dogs) were repeated at a 2-week interval. Coronary angiography revealed that in Group A, antegrade flow in the LAD distal to the occlusion, which was assessed by Thrombolysis in Myocardial Infarction (TIMI) grade, was significantly increased after treatment. In contrast, in Groups B and C, the treatment did not change the flow grade in the LAD. In Group A, the regional myocardial blood flow in the collateral dependent area was significantly increased after treatment, and the regional myocardial blood flow reserve after adenosine injection was also significantly increased. These measurements remained after treatment in Groups B and C. The immunohistochemical study with factor VIII-related antigen revealed an increase of vascular density in the ischemic region in Group A. Intramyocardial delivery of bFGF-impregnated AGHM, but not free-form bFGF, improves the collateral circulation to the infarct area of a coronary occlusion in dogs.

A study on the effects of endogenous nitric oxide on coronary blood flow, myocardial oxygen extraction and cardiac contractility.

The purpose of the present study was to clarify how endogenous nitric oxide (NO) affects cardiac contractility and myocardial oxygen consumption (MVO2) in vivo. alpha-Chloralose-anesthetized dogs (n = 18) were instrumented to perform continuous and simultaneous measurements of coronary blood flow (CBF), anterior interventricular vein oxygen saturation (with the use of a fiberoptic catheter), aortic pressure, left ventricular pressure, and left ventricular volume. CBF, myocardial oxygen extraction (O2-extract), MVO2, the relationship between CBF and O2-extract during direct vasodilation induced by intracoronary papaverine (0.1, 0.2, 0.4 mg/kg), and cardiac contractility (Emax) were examined at control, after intracoronary infusion of NG-monomethyl-L-arginine (L-NMMA, 2 mg/kg) and after antagonization of NO by L-arginine (20 mg/kg). L-NMMA decreased CBF from 62.0 +/- 1.7 to 59.7 +/- 2.4 (mL/min/100 g, P < 0.05) and increased O2-extract from 68.2 +/- 1.7 to 79.0 +/- 1.7% (P < 0.05). Emax was increased after L-NMMA from 3.2 +/- 0.2 to 3.7 +/- 0.1 (mmHg/mL/100 g, P < 0.05). These effects of L-NMMA were antagonized by L-arginine (P < 0.05 vs. after L-NMMA, P = NS vs. before L-NMMA). L-NMMA shifted CBF and O2-extract relationship determined by papaverine injection upward and L-arginine antagonized it to its baseline level. Endogenous NO reduces cardiac contractility and decreases MVO2, while increasing CBF.

Nitric oxide modulates cardiac contractility and oxygen consumption without changing contractile efficiency.

Nitric oxide (NO) affects myocardial contractility and myocardial oxygen consumption (MVO2) in vitro. In alpha-chloralose-anesthetized dogs instrumented for the measurements of left ventricular (LV) pressure, LV volume using a conductance catheter, coronary blood flow, and coronary venous oxygen saturation (ScvO2) using a fiber-optic catheter, LV end-systolic pressure-volume relationships (ESPVR) and the relationship between MVO2 and LV pressure-volume area (PVA) were analyzed before and after intravenous infusions of the NO synthase inhibitor NG-monomethyl-L-arginine acetate (L-NMMA; 5 mg/kg, 8 dogs) and the NO substrate L-arginine (600 mg/kg, 7 dogs). L-NMMA increased the slope of the ESPVR (Emax) (P < 0.05) without changing contractile efficiency indicated by the inverse of the slope of the MVO2-PVA line. L-NMMA also increased unloaded MVO2, indicated by the y-axis intercept of the MVO2-PVA line (P < 0.05). In contrast, L-arginine decreased Emax (P < 0.05) while decreasing MVO2 (P < 0.05), and without changing contractile efficiency. The basal oxygen metabolism was not affected by L-NMMA and L-arginine. These data imply that endogenous NO spares MVO2 by reducing oxygen use in excitation-contraction coupling and attenuates cardiac contractility without changing contractile efficiency.

Cardiac sympathetic stimulation increases cardiac contractility but decreases contractile efficiency in canine hearts in vivo.

The effect of cardiac sympathetic stimulation on cardiac contractile efficiency was studied in dogs. In 19 anesthetized and open-chest dogs, left ventricular (LV) pressure, LV volume, coronary blood flow and coronary venous oxygen saturation were measured simultaneously. The LV end-systolic pressure volume relations (ESPVR) and the relation between myocardial oxygen consumption (VO2)-pressure volume area (PVA) were obtained during a transient occlusion of the inferior vena cava before and after sympathetic stimulation (9V, 6 Hz, 40 sec) both with and without 50 mg/kg of 2,3-butanedione monoxime (BDM). Without BDM, sympathetic stimulation increased the slope of ESPVR by 62% (p<0.05), the slope of the VO2-PVA line by 19% (p<0.05) and the y-axis intercept of the VO2-PVA by 65% (p<0.05). With BDM, the increase in the slope of the VO2-PVA line became insignificant although other responses were similarly preserved. These data imply that cardiac sympathetic stimulation decreases cardiac contractile efficiency through mechanisms by which norepinephrine-induced beta-adrenergic activation enhances myosin ATPase-operating ATP hydrolysis in crossbridge formation.

Effects of cardiac sympathetic nerve stimulation on the left ventricular end-systolic pressure-volume relationship and plasma norepinephrine dynamics in dogs.

The effects of cardiac sympathetic nerve (CSN) stimulation on the left ventricular end-systolic pressure-volume relationship (ESPVR) and plasma norepinephrine (NE) concentration in arterial blood were studied in dogs. In 12 anesthetized and open-chest dogs, left ventricular pressure and volume were measured simultaneously with a microtip catheter and a conductance catheter, respectively. The ESPVR values were constructed from pressure-volume loops during a brief occlusion of the inferior vena cava before and after a 40-sec train of electrical CSN stimulation. The slope (Emax) of the ESPVR line was significantly greater after CSN stimulation than before CSN stimulation (p < 0.05) for both right and left CSN stimulation. The increased Emax values after right and left CSN stimulation were not significantly different from each other. In 5 dogs, time courses of Emax, left ventricular systolic pressure, heart rate, and plasma NE concentration after CSN stimulation were studied. Left ventricular systolic pressure and heart rate returned to the baseline more rapidly than Emax and arterial plasma NE concentration. There was a positive, linear correlation between Emax (y) and arterial plasma NE concentration (x), shown as y = 3.3 x 10(-3)x + 3.1 (n = 30, r = 0.86, p < 0.05). These results imply that cardiac contractile enhancement is reflected in arterial plasma NE concentration in conditions in which CSN is activated.

Analysis of catalytic action of transglutaminase induced in human promyelocytic leukemia (HL-60) and human hepatoblastoma (HepG2) cells.

Transglutaminase is a calcium-dependent enzyme that catalyzes an amine incorporation and a cross-linking of proteins. Intracellular transglutaminase is induced when human promyelocytic leukemia HL-60 cells are treated with retinoic acid and human hepatoblastoma HepG2 cells, with interleukin-6. To find whether the intracellular reaction catalyzed by transglutaminase increased when the enzyme is induced in these cells, the transglutaminase-catalyzed incorporation of 14C-labeled methylamine into cellular proteins was measured. The incorporation level of the labeled methylamine into proteins of HL-60 and HepG2 cells did not increase after the transglutaminase had been induced. The presence of the calcium ionophore A23187 did not affect these results. These findings suggested that even after the enzyme induction the catalytic action of intracellular transglutaminase is maintained at a constant level in these cells by unknown regulatory mechanism(s).

Increase caused by interleukin-6 in promoter activity of guinea pig liver transglutaminase gene.

A 5'-flanking region (-2024 to +61) of the guinea pig liver transglutaminase gene and some 5'-deletion mutants were tested for promoter activity in human hepatoblastoma HepG2 cells treated with interleukin-6 (IL-6) by an assay of the transient expression of the chloramphenicol acetyltransferase reporter gene. The promoter activity of the 5'-flanking region introduced into the HepG2 cells was increased by IL-6.

[Experimental test of a model of memory-representation-generation in learning and recognition].

A highly structured set of stimuli was used in this study. Each stimulus had four binary attributes, whose values were determined so that any two stimuli could be transformed into each other by changing values of one or more attributes. In one experiment, 93 undergraduates rated similarity of paired stimuli. In another experiment, the same subjects learned three stimuli which were presented one after another for 10 seconds each. Later, in the recognition task, they made "old" or "new" judgment and rated the confidence of their judgment for each of the test stimuli. Two groups of subjects served the two experiments in different order. The results showed that (1) the rated similarity between the paired stimuli is a monotonically decreasing function of the number of transformations needed to get the pair equal, (2) the recognition confidence for new stimuli is significantly higher for stimuli generated by relevant transformations from the learned stimuli than for stimuli not so generated. The results support a model of memory-representation-generation (Suto, 1987, 1988), but not "prototype plus transformation model" nor "context model".

Expression induced by interleukin-6 of tissue-type transglutaminase in human hepatoblastoma HepG2 cells.

We examined the effect of interleukin-6 (IL-6) on the expression of transglutaminase in human hepatoblastoma HepG2 cells. Treatment of cells with IL-6 increased their transglutaminase activity in a time- and dose-dependent way. Dexamethasone strengthened the stimulation by IL-6. Half-maximum stimulation of transglutaminase activity in the cells occurred at a dose of 40 pM IL-6 regardless of the presence of dexamethasone. Based on its immunoreactivity, the transglutaminase induced was identified as tissue-type transglutaminase. Immunoblot analysis showed that the increase in transglutaminase activity was related to an increase in the amount of transglutaminase protein. Northern blot analysis with a cDNA probe specific for human tissue-type transglutaminase showed that exposure of HepG2 cells to IL-6 increased the mRNA level of the enzyme, and the increase was detectable 3 h after IL-6 was added. Induction of the mRNA was maximum between 10 and 14 h. The increase in the mRNA level was not blocked by the presence of cycloheximide, suggesting that the increase was independent of protein synthesis. Injections into mice of substances that induce inflammation such as turpentine and lipopolysaccharides increased the liver transglutaminase activity. These results indicated that transglutaminase may be involved in some biological processes in hepatocytes regulated by IL-6 signaling.

Identification of promoter region of guinea pig liver transglutaminase gene.

A 5' flanking region of the guinea pig liver transglutaminase gene was cloned and sequenced. The sequences for TATA box and potential binding sites of some regulatory factors were found in this region. The promoter activity of this region was shown by transfecting its fusion-construct with the chloramphenicol acetyltransferase gene into human hepatoblastoma HepG2 cells.

[The dynamic changes in the confidence of recognition in the learning of a highly structured set of stimuli].

In this study using a highly structured set of stimuli, each stimulus had five attributes and each attribute could take one of two values. Two stimuli were selected from the set for the control condition and three for the experimental condition. Two learned stimuli in the control condition were those which could be transformed between one another by four relevant transformations. Among the not-learned stimuli a few stimuli were related to the learned stimuli by relevant transformations and were called generative stimuli, while the leftover stimuli were called ungenerative stimuli. In the experiment, the subjects memorized two or three learned stimuli and immediately recalled them. After several minutes of an inserted task, they made "old" or "new" judgments of the test stimuli and then rated their own confidence of judgment. The experimental results showed that; (a) the recognition confidence was highest for the learned stimuli, the second highest for the generative stimuli, and lowest for the ungenerative stimuli, and (b) the learning of the third stimulus increases the confidence of the generative stimuli. The main conclusion is that the recognition confidence for the test stimuli systematically change, as stimuli in a highly structured set of stimuli are learned one after the other.

[Effects of repeated presentation of stimuli on the learning and recognition of a highly structured set of stimuli].

In this article, we report the results of two experiments which investigated the repetition effect of stimulus presentation on recognition judgement. Each stimulus in sets of stimuli had five or six binary attributes. Any two stimuli could be mutually transformed by changing values of some attributes. In the experiments, subjects learned and immediately recalled stimuli, presented one after another. Learning was repeated several times. In the following recognition task, subjects were presented, one after another, the set of test stimuli consisted of old and new stimuli and judged whether each stimulus was old or new, and rated the degree of confidence of the judgement. The results showed that when learning of the presented stimuli progressed, the degree of the confidence of 'old' judgement increased for the presented stimuli, while for the new stimuli, it increased, at first, and then decline.

Activity and gene expression of transglutaminase in guinea pig liver during the postnatal growing phase.

During the postnatal growing phase from birth to 7 weeks old, the cytosolic transglutaminase activity of guinea pig liver increased 3.8-fold. The enzyme activity in the particulate fraction increased slightly. Immunoblot analyses showed that the postnatal increase in the activity was correlated with in increase in the enzyme protein. The quantity of mRNA of the liver transglutaminase did not change significantly during the postnatal growing phase examined. These results indicated that transglutaminase may be involved in the postnatal development of guinea pig liver and that the amount of transglutaminase in the postnatal liver may be controlled post-transcriptionally.