摘要:

SUMMARYThe cardiovascular actions of serotonin and its antagonists are reviewed with a view to clarifying whether serotonin has a role in blood pressure control through actions on the peripheral vasculature. Serotonin has complex actions in the heart and vasculature but none of these actions is completely understood. There is no doubt, however, that serotonin has extensive interactions with the sympathetic nervous system. The nature of the serotonin receptor is also discussed. There is extensive evidence that more than one type of serotonin receptor exists. Biochemical studies in brain homogenates have delineated two sub‐populations of serotonin receptors, named 5HT1and 5HT2. It is not clear whether the same receptor types exist in the vasculature but various actions of serotonin on the vasculature have tentatively been ascribed to actions on 5HT1‐ and 5HT2‐type receptors. It is clear that there is some functional overlap between serotonin‐receptors and α‐adrenoceptors. The mechanism by which this overlap could occur is unknown although we suggest it may result from a physical overlap of serotonin receptors and α‐adrenoceptors. Compounds which antagonize serotonin have provided the means for investigating serotonin receptors but have not clarified the role of serotonin in blood pressure control; certainly they have comparatively little effect on blood pressure and this may simply reflect the lack of free circulating serotonin. In animal studies the new serotonin antagonist ketanserin appears to lower blood pressure via α‐adren

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. An isolated and perfused preparation of rat ileum was used to investigate the effects of cholinergic, adrenergic and bombesin stimuli on neurotensin release into the vascular compartment.2. A vigorous release of neurotensin like immunoreactivity (NTLI) to 200% above basal values in response to intraluminal infusions of emulsified soybean oil (Intralipid) demonstrated the physiological responsiveness of the preparation.3. Carbachol significantly stimulated the release of both NTLI and bombesin like immunoreactivity (BLI), with maximal responses at 5 times 10‐9mol/l carbachol of 100% and 400% above basal values for NTLI and BLI, respectively.4. Noradrenaline at 10‐6and 10‐4mol/l caused no significant release of NTLI but markedly inhibited spontaneous BLI release.5. Synthetic amphibian bombesin caused a marked release of NTLI to 81% and 100% above basal at infusion concentrations of 5 times 10‐11and 5 times 10‐10mol/l respectively.6. These results suggest that there is either a direct effect of cholinergic agents on the N cells bringing about NTLI release, or an indirect effect via the release of bombesin like peptides from intrinsic gut neurones. This preparation provides a useful model to study the complex neural, paracrine and endocrine interactions in the gastrointesti

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. Using the abdominal constriction test in mice it was shown that the antinociceptive effect of morphine was inhibited by naloxone hydrochloride and its quaternary derivative naloxone methylbromide which presumably only acts peripherally.2. Pretreatment with a single dose of morphine 2.0 mg/kg s.c. did not alter the antinociceptive effect of a second dose of morphine given 3 h later. However, the antagonistic effect of naloxone against morphine was enhanced at this time.3. The development of increased naloxone potency was inhibited when naloxone hydrochloride was given together with morphine in the pretreatment.4. A similar inhibitory effect was observed when the quarternary derivative naloxone methylbromide was used instead of naloxone hydrochloride in the pretreatment regime.5. As there was no difference between the effects of naloxone hydrochloride and naloxone methylbromide in suppressing the development of increased naloxone potency induced by morphine pretreatment, it was concluded that this phenomenon may be mediated mainly through peripheral opiate receptors.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. Splanchnic blood flow is generally considered to be one of the major factors governing the efficiency of peritoneal dialysis; however, few direct measurements of blood flow have been made during peritoneal dialysis.2. The radioactive microsphere technique was used to assess the effects of 1.5 and 4.25 g/100 ml dextrose‐Dianeal solutions on blood flow to various tissues in the abdominal cavity. The effects of dialysis solution on blood flow through the superior mesenteric and coeliac arteries were measured by electromagnetic flowmetry.3. The results indicate that the commercial peritoneal dialysis solutions dramatically increase blood flow to the mesentery, omentum, intestinal serosa and parietal peritoneum. These changes are not accompanied by significant alterations in blood perfusion in the major abdominal organs (liver, stomach, intestine, pancreas, spleen). Peritoneal dialysis solutions do not significantly alter blood flow through the coeliac and superior mesenteric arteries.4. These findings indicate that commercial dialysis solutions improve perfusion to the peritoneum without significantly altering splanchnic blood flo

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00855.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. The short term effects of the novel diuretic MK 447 were examined in both normotensive and hypertensive (ACTH treated) conscious sheep.2. The drug had profound diuretic, natriuretic and kaliuretic effects in both groups. Plasma sodium was unchanged but plasma potassium fell and haematocrit increased. Plasma renin concentration increased with MK 447 in the normotensive but not the hypertensive sheep.3. In the normotensive sheep cardiac output fell, peripheral resistance increased and blood pressure was unchanged. In the hypertensive ACTH treated sheep cardiac output and blood pressure fell but resistance was unchanged.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00856.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. The effects of chronic thyroxine treatment on cat soleus muscle contractions were studied.2. Maximum twitch tension, contraction time, half relaxation time and tensiontime integral of maximal twitches of the soleus muscles of thyroxine treated cats were significantly decreased. Consequently, there was a decrease in tension and degree of fusion of incomplete tetanic contractions of the soleus muscle. The maximum tetanic tension was not statistically significantly changed, suggesting that the effects may be due to a decrease in the duration of the active state of the muscle.3. Isoprenaline given intravenously during incomplete tetanic contractions of the soleus muscle caused a statistically significant depression of tension in the control group but not in the thyroxine treated group. This further suggests reduction in the duration of the active state of soleus muscles of thyroxine treated cats.4. Propranolol injected chronically with thyroxine reversed or prevented the depression of tension caused by thyroxine treatment, suggesting the involvement of β‐adrenoceptors in these effects.5. The decrease in tension and degree of fusion during incomplete tetanic contractions of the thyroxine treated soleus could be responsible, at least partly, for the muscle weakness and tremor of thyrotoxicosis. Cyclic AMP may possibly be the mediator of these effec

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00857.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. Angiotensin converting enzyme (ACE) activity in fetal lung and placenta was determined by the method of Cushman and Cheung (1971) during the second trimester of human pregnancy and throughout the rat gestation. The enzyme activity in the neonatal rat lung was also determined during the first 19 days of life.2. The enzyme activity in both tissues of both species increased with gestation. The activity in human fetal lung at the end of the second trimester was already 70% of that present in the adult human lung while rat fetal lung enzyme activity at term was only 15% of the adult value. The activity in the term placenta of the human and rat was respectively 13% and 5% that of the adult lung value. Developmental increases in enzyme activity continued in the neonatal rat lung till adult value at about 19 days postpartum.3. The pattern of fetal lung enzyme development in the rat resembled that of the rabbit fetal lung as determined by other investigators using different techniques but was different from that of the human.4. The findings support the suggestion that ACE in the lung and placenta play important roles in the maintenance of circulatory homeostasis during the latter part of gestation, at birth and early postpartum, albeit at a different extent in different species.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00858.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. Plasma levels of aldosterone, corticosterone, potassium and renin activity, and urinary potassium excretion, were measured in control (CK) rats, and in rats adapted to a high potassium diet (HK), before and after an acute intragastric KCl load.2. Prior to the KCl load there was no difference in plasma potassium (K) or plasma aldosterone.3. Following the KCl load, HK rats maintained a lower plasma K, and, except at 30 min after the load, a lower plasma aldosterone than CK rats.4. At a low plasma K there was no difference in plasma aldosterone between CK and HK rats. At a high plasma K (>8 mmol/l) the HK rats had a higher plasma aldosterone for the same plasma K than CK rats.5. The enhanced ability to excrete an acute K load seen in HK rats seems unlikely to be due to higher levels of plasma aldosterone.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00859.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. The effects of vasopressin infusion on hepatic artery flow was studied in rats.2. Hepatic artery ligation followed by the infusion of vasopressin (0.08 μU/g body weight per min) decreases portal venous flow and liver blood flow.3. Vasopressin infusion results in an increase in hepatic artery flow and liver blood flow both of which are abolished by subsequent hepatic artery ligation.4. The increase in hepatic artery flow and the decrease in portal venous flow following the infusion of vasopressin is discussed in relation to the management of patients presenting with bleeding oesophageal varices

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00860.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

SUMMARY1. The use of a low Na, low K sorghum grain diet supplemented with intraruminal electrolyte infusions has enabled dietary manipulation of sodium status to be studied in the sheep.2. Dietary sodium restriction reduced urinary sodium excretion within 24 h with maximal retention after 3 days. There were no other substantial metabolic or haemodynamic changes.3. A more severe form of sodium deficiency produced by parotid salivary drainage resulted after only 2 days in a sodium deficit 3–4 times that seen with 14 days of sodium restriction. Extracellular fluid volume and cardiac output decreased. Blood pressure was unchanged but there was an increase in peripheral resistance and plasma renin concentratio

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1984.tb00861.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY