摘要:

The acute potentiating effect of ouabain on norepinephrine (NE) induced contractions of isolated rabbit aorta was investigated. Ouabain, at concentrations of 3 × 10–7 to 10–5 mol/l potentiated the vasoconstrictor effect of NE as demonstrated by a shift to the left of the NE concentration-response curve in a parallel manner and a concentration-dependent increase in the EC50 ratio. A significant increase in maximal contractility was observed by ouabain at 3 X 10–6 and 10–5 mol/l. Removal of the endothelium did not alter the effect of 10–5 mol/l ouabain. When the NE concentration-response curves were again determined after ouabain had been washed out, it was found that the ouabain-induced increase in EC50 ratios returned to control values, while the increase in maximal contractility did not. The slopes of the NE concentration-response curves were not significantly different in the presence of ouabain than control values, but were higher when obtained after ouabain had been

ISSN:0031-7012    

DOI:10.1159/000138449

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The adenosine potentiating drugs dilazep and lidoflazine were studied for their relaxing ability in isolated dog cerebral and renal arteries contracted under conditions which induce the opening of potential-dependent calcium channels (using K+ at 30, 50 and 100 mmol/l) and under conditions which induce the opening of receptor-operated calcium channels (prostaglandin F2α, PGF2α; 5-hydroxytryptamine, 5-HT) and compared with those of adenosine and a standard calcium entry blocker, diltiazem. Dilazep, lidoflazine and diltiazem exerted concentration-dependent relaxation in cerebral and renal artery ring strips contracted with 30, 50 and 100 mmol/l K+. However, dilazep was slightly more potent at 100 mmol/l K+. In contrast, whereas the high concentration of adenosine (1 × 10–5–3.7 × 10–4 mol/l) relaxes these arteries only at 30 mmol/l K+, it produced a more pronounced concentration-dependent relaxation when PGF2α dilazep, respectively. Adenosine deaminase reversed the relaxation produced by adenosine, but was unable to reverse the relaxing responses to diltiazem, lidoflazine and dilazep. These findings suggest that dilazep and lidoflazine have a direct relaxing effect independent of adenosine in cerebral and renal artery ring strips possibly through their calcium entry blocking activity. The data suggest that adenosine is more effective on the receptor-operated contractions, whereas dilazep and lidoflazine are more effective on the potential-dependent co

ISSN:0031-7012    

DOI:10.1159/000138450

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The effects of nisoldipine on myocardial performance and large coronary artery diameter, resistance and cross-sectional area were studied in rabbit hearts in situ. Changes in mean internal diameter of coronary artery segments were visualized using color arteriography; changes were computer-calculated. Nisoldipine had a direct dilatory effect on large coronary arteries in situ and it attenuated the vasoconstriction induced by vasopressin. It shifted the dose-response curve of vasopressin to the right in a noncompetitive manner. Nisoldipine reduced the effect of vasopressin on maximum left ventricular dP/dt, mean aortic pressure, left ventricular end-systolic pressure and heart rate. The results demonstrate that nisoldipine is an effective dilator of large epicardial coronary arteries in situ and inhibits the vasoconstriction induced by vasopressin.

ISSN:0031-7012    

DOI:10.1159/000138451

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The effects of the α1-adrenergic agonist phenylephrine (PE) and the phorbol ester 4β-phorbolmyristate-acetate (PMA) on sodium pump function were studied in the rat liver. In order to distinguish between direct and indirect influences, ouabain-sensitive 86Rb uptake by intact liver slices was compared with ouabain-sensitive Na+/K+-ATPase activity in plasma membranes isolated from PE and PMA-perfused livers. At a buffer Ca2+ level of 2.5 mmol/l, PE (10 μmol/l) caused an initial stimulation of both 86Rb uptake and Na+/K+-ATPase activity followed at 5 min by a decrease in both activities. Both actions were blocked by the α1 -antagonist prazosin. The decrease in ouabain-sensitive Na+/K+-ATPase was paralleled by an increase in Mg2+ ATPase activity. At a Ca2+ level of 1.5 mmol/l, PE stimulation of 86Rb uptake and Na+/K+-ATPase was sustained, and the inhibitory component was not expressed. PMA (4 μmol/l) reduced 86Rb uptake and Na+/K+-ATPase and similar to PE, this inhibition was paralleled by an increase of Mg2+-ATPase activity. 4α-PMA, which does not activate protein kinase C, failed to influence 86Rb uptake or Na+/K+-ATPase. These results demonstrate that PE and PMA effects on ouabain-sensitive 86Rb uptake are preserved in isolated membranes, indicating a direct influence on the Na+/K+-ATPase. A role for protein kinase C in modulating sodium pump activity is sugg

ISSN:0031-7012    

DOI:10.1159/000138452

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

In male Tuck AHA rats, restraint stress had no effect on 5-hydroxytryptamine (5-HT) levels in the frontal cortex, amygdala, hypothalamus and hippocampus, but produced a significant increase in 5-hydroxyindoleacetic acid (5-HIAA) levels in the amygdala after 120 and 180 min, and in the hypothalamus after 180 min. This apparent increase in turnover was not paralleled by a concomitant increase in the rate of 5-HT synthesis, as determined by measuring the accumulation of 5-hydroxytryptophan (5-HTP) following inhibition of amino acid decarboxylase with m-hydroxybenzylhydrazine (NSD-1015). 5-HTP accumulation was, however, increased in the frontal cortex after 180 min. In naive rats, buspirone (0.1–2.5 mg/kg, s.c.) produced a dose-dependent decrease in 5-HTP accumulation in all four brain regions, while chlordiazepoxide, in doses up to 10 mg/kg (s.c.) had no effect. The increase in 5-HT synthesis in the frontal cortex following 180 min restraint stress was inhibited by pretreatment with buspirone, when administered at 2.5 mg/kg (s.c.) 30 min prior to the stress period, but not by chlordiazepoxide at 10 mg/kg (s.c

ISSN:0031-7012    

DOI:10.1159/000138453

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

In view of the analgesic effects produced by cathinone (CATH), an amphetamine-like agent, and of the interaction of amphetamines with stressful environmental stimuli, the present study evaluated in rats the influence of CATH on the nonopioid analgesia induced by a brief electric footshock (FSA; 3 min of continuous 2.5 mA current). The influence of this combination on body temperature was also evaluated. CATH (5 mg/kg, i.p.) alone induced a brief and slight increase in latency during the hot plate test (HPT), but enhanced and prolonged the analgesic effect induced by FS. In addition, the presentation of the environment (shock box with unelectrified grid) where other rats received FS, caused CATH to induce a slow-rising analgesic effect for 180 min. A hyperthermic response paralleling the analgesic effect was observed in shocked and nonshocked rats receiving CATH. After 24 h, rats that had received both CATH and FS on the previous day showed prolonged latencies on the HPT before and after a 1-min presentation of unelectrified grid. These animals also showed an increased analgesic response to the subsequent application of a 15-second FS. At the same time no differences in body temperature were observed between treatment groups. These results suggest that CATH can interact with environmental stimuli to induce an analgesic effect, the time-course of which depends upon the intensity of the stimulus applied.

ISSN:0031-7012    

DOI:10.1159/000138454

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

Sodium was measured in β-cell-rich pancreatic islets isolated from ob/ob-mice starved overnight. Exposure to glucose (5 or 20 mmol/l) resulted in about a 30% reduction of the sodium content whether or not the Na+/K+ pump was inhibited by removal of K+. The glucose effect was not potentiated after amiloride depression of Na+/H+ exchange, and it disappeared when combining removal of K+ with the addition of the hyperglycemic sulphonamide diazoxide (400 μmol/l). Tolbutamide (100 μmol/l) counteracted the reduction of sodium obtained with 5 mmol/l glucose both in the presence or absence of extracellular K+. It is concluded that closure of ATP-regulated K+ channels does not necessarily result in a lowering of the sodium content. The pancreatic β-cells can be regarded as exceptional among the excitable cells in not responding to their natural physiological stimulus (glucose) with increase of sod

ISSN:0031-7012    

DOI:10.1159/000138455

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

In normal female sheep, we investigated effects of exercise on the absorption of atropine sulfate (0.02 mg/kg) given intramuscularly. The exercise regime consisted of treadmill running (20 min at 3–4 mph at 0° grade) starting immediately after intramuscular atropine injection into the biceps femoris. Six normal female sheep received intramuscular atropine and 7–14 days later an identical intramuscular dose of atropine with exercise. Serum levels of atropine measured by radioimmunoassay were monitored over a 6-hour period. The time to peak concentration was significantly less with exercise than without, 2.9 ± 2.1 and 13.7 ± 5.4 min, respectively (p < 0.005). In addition, peak serum atropine concentrations tended to be higher, 9.7 ± 1.3 ng/ml with exercise versus 7.1 ± 2.9 ng/ml without exercise; however, the difference did not attain statistical significance (p < 0.08). This study demonstrates that exercise increases the early absorption of intramuscularly administered atropine

ISSN:0031-7012    

DOI:10.1159/000138456

出版商:S. Karger AG    

年代:1988

数据来源: Karger