摘要:

SUMMARY1. The effects of various drugs have been studied on blood flow and oxygen handling (availability, extraction and consumption) in both normal and acutely ischaemic regions of the canine myocardium. Ischaemia was produced by the acute ligation of the anterior descending branch of the left coronary artery.2. Lidoflazine, like other coronary vasodilator drugs, increases blood flow in the normal myocardium, but does not increase flow through the ischaemic region. Drugs of this type may, in addition, open up ‘shunt’ vessels within the ischaemic region.3. Of three cardiac stimulants studied, only oxyfedrine consistently increases blood flow through the ischaemic region; isoprenaline and glucagon do not.4. Noradrenaline causes marked increases in flow through the ischaemic region: its effect is associated with an increase in coronary pressure in the artery distal to the ligature.5. Evidence is put forward that the critical factor determining flow through ischaemic regions of the myocardium is the transventricular driving pressure. When the effects of various drugs on flow and driving pressure are analysed and compared, the only drugs that increase flow in an ischaemic region are those that increase the pressure gradient across the wall of the left ventri

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00531.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Dantrolene depresses the tension of directly or indirectly elicited twitches and tetaní of the tíbíalís anteríor and soleus muscles of cats under chloralose anaesthesia, without affecting the gross muscle action potentials.2. The decrease in twitch tension is associated with slowed rates of rise of tension and of relaxation, but there is no change in the time to peak tension. The decrease in maximal tetanic tension is associated with a slowed rate of rise of tension, but there is no change in the rate of relaxation. It is concluded that dantrolene decreases the intensity of the active state, possibly by impairing the release of Ca2+from the sarcoplasmic reticulum.3. The soleus muscle is slightly more resistant than the tibialis anterior muscle to the action of dantrolene, and maximal tetani of both muscles are much more resistant than twitches.4. Adrenaline, theophylline and quazodine produce effects on the dantrolene‐depressed twitches that are proportionately the same as those produced on the control twitches; there is no evidence of a specific antagonistic effect of any of these drugs.5. Tetanic stimulation of the tibialis anterior muscle but not the soleus muscle causes a temporary relief of the twitch depression produced by dant

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00532.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The actions have been compared of the acetylcholine antagonists, hexamethonium, tuborcurarine, pancuronium and gallamine on the effects of neostigmine at the neuromuscular junction of the soleus muscle in cats under chloralose anaesthesia.2. Neostigmine produced augmentation of twitch tension, muscle fasciculations, repetitive firing in the muscle and antidromic repetitive firing in the ventral roots: all these effects were blocked by the acetylcholine antagonists. The effective doses of hexamethonium were similar to its ganglion blocking doses, being much smaller than those necessary to block the normal soleus twitch, and it is concluded that the effects of neostigmine arise mainly from the action of preserved transmitter (acetylcholine) on the motor nerve endings.3. In the smallest effective doses, hexamethonium preferentially blocked muscle fasciculations and the associated electrical activity in nerve. Tubocurarine, which has considerable ganglion blocking activity (reflecting its affinity for neuronal cholinoceptors) resembled hexamethonium. In contrast, pancuronium and gallamine, which are considered to have a higher affinity for post‐junctional muscle cholinoceptors, depressed muscle fasciculations only in doses that also depressed twitch augmentation and repetitive firing in muscle.4. In slightly larger doses, pancuronium and gallamine also blocked antidromic repetitive firing in nerve indicating that these drugs also combine with prejunctional neuronal cholinoceptors, and suggesting that these cholinoceptors are intermediate in character between ganglionic and muscle cholinoceptor

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00533.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Contractions of guinea‐pig isolated vasa deferentia produced by noradrenaline were found to consist of several phases. The sustained part of the contraction was very small compared with maximal contractions produced by stimulation of the postganglionic nerves. The sustained phase was usually preceded by a rapid phasic contraction and in some experiments was followed by contraction on washing out the noradrenaline.2. Contractions in response to noradrenaline were blocked by the α‐adrenoceptor antagonist, phentolamine.3. Noradrenaline‐induced contractions were inhibited in the presence of low conditioning doses of noradrenaline, phenylephrine, oxymetazoline or methoxamine. This effect may provide an explanation for the observation that noradrenaline inhibits contractions produced by sympathetic nerve stimulation. Although it was presumably mediated via α‐adrenoceptors the inhibitory effect was not due to depolarization alone since it could not be reproduced by increasing the potassium concentration of the Krebs solution.4. The α‐receptor agonists inhibited responses to noradrenaline or phenylephrine, but augmented potassium and acetylcholine contractions. This specificity of action eliminates the possibility that a distinct group of α‐receptors solely mediating a relaxant effect were activated in these experiments but suggests receptor desensitization.5. Receptor‐specific desensitization was also found to be a property of the acetylcholine rec

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00534.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Averaged evoked potentials in response to light flashes were recorded from the scalp in conscious, restrained rabbits. Six sedative and three stimulant drugs were administered intravenously and their effects on the evoked potential were measured2. All six sedative drugs reduced the amplitude of the surface‐negative wave occurring 150–200 ms after the stimulus, whereas all three stimulants increased the size of this component. No such consistency was found in drug effects on the early surface‐positive wave.3. The results obtained support the hypothesis that the size of certain components of sensory averaged evoked potentials is related to the level of behavioural ar

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00535.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Anaesthetized rats were infused intravenously for 1 h with a specific antagonist of angiotensin II, 1‐Sar‐8‐Ala‐angiotensin II (P‐113), at a rate of 5 μ/kg per min, or with saline.2. Blood samples were taken, before and after infusion, for measurement of plasma renin activity (PRA) and plasma renin concentration (PRC).3. Saline infusion did not affect PRA or PRC.4. Infusion of P‐113 produced steep and highly significant increases in PRA (652%) and PRC (724%), despite a slight rise in mean arterial pressure.5. Within 30 min of terminating P‐113 infusion, PRA fell to 300%, and PRC to 278% of pre‐infusion levels, and subsequently continued to fall.6. It is suggested that the hypersecretion of renin produced by P‐113 is due to blockade of the inhibitory control normally exerted by endogenous angiotensin I

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00536.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Plasma renin activity (PRA) was studied in rats and rabbits actively immunized against angiotensin II (A II).2. The mean PRA values (in ng angiotensin I/ml per h) were 3.5 (s.e.m. = 0.4) in ten control mock‐immunized rats, and 3.3 (s.e.m. = 0.5) in seven rats having demonstrable sustained immunity to A II.3. In six unanaesthetized rabbits, the appearance of antibody directed against A II was associated with a 263% increase in PRA during the first week, whereas the PRA of five control mock‐immunized rabbits, tested at the same stage, exhibited no such change.4. The PRA returned to control values by 3 months in the rabbits immunized against A II, although the antibody titres remained high.5. The finding of significantly elevated PRA early in the course of production of antibody against A II is consistent with the properties of a negative feedback system, the renin hypersecretion being provoked by partial blockade of the normal inhibitory effect of A II on renin release. However, in chronically immune animals, the PRA is nor

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00537.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The concentrations of aldosterone, corticosterone, cortisol and renin substrate in plasma and the plasma renin activity were determined in five non‐pregnant and five pregnant rhesus monkeys.2. The mean aldosterone concentrations are 25.9 ng/100 ml in the non‐pregnant and 31.4 ng/100 ml in the pregnant monkey: the difference is not significant (P>0.5).3. The mean corticosterone concentrations are 1.11 and 1.84 μg/100 ml respectively: the difference is not significant (P>0.1).4. The mean cortisol concentrations are 21.3 and 28.2 μg/100 ml respectively: the difference is significant (P<0.05).5. Pregnancy does not result in increases in either plasma renin activity, mean values being 4.96 and 3.72 ng/ml per h, respectively, or renin substrate concentrations, the means being 1.09 and 0.82 μg/ml, respectively.6. The lack of elevation of these hormones is consistent with findings that concentrations of progesterone and oestrogen are only slightly increased in pregnancy in rhesus m

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00538.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The incubation of kangaroo renin‐substrate with renin from kangaroo, hog or sheep yields angiotensin having pressor activity in the rat.2. Kangaroo angiotensin I is not reactive in radioimmunoassay which is sensitive to other forms of angiotensin I.3. Kangaroo angiotensin I is converted by passage through the rat pulmonary circulation or by equine converting enzyme to a reactive product in radioimmunoassay for angiotensin II.4. The findings suggest that the amino acid sequence of kangaroo angiotensin I differs from that of other known angiotensin

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00539.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY