摘要:

The effect of menthol on the urinary bladder cooling reflex was studied in α‐chloralose‐anaesthetized cats. The cooling reflex was elicited by bladder or urethral instillations of cold saline and monitored by multiunit recordings from efferent and afferent pelvic nerve filaments. The bladder cooling reflex was greatly exaggerated by intraluminal exposure of the bladder or the urethra to a 0.6 mmsolution of menthol. The effect occurred without a sensitizing effect on bladder mechanoreceptors. It could be described as a shift of the temperature‐response curve for the cooling reflex towards higher temperatures. This change resembles the effect of menthol on cutaneous cold receptors. It is proposed that the bladder cooling reflex originates from cold receptors in the bladder and urethral

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09037.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Isolated detrusor muscle from control cats and cats parasympathetically decentralized for 3 and 10 weeks responded to electrical field stimulation by tetrodotoxin‐sensitive, frequency‐dependent contractions. There were no significant differences in the frequencies producing 50% response. However, the amplitude of the scopolamine‐resistant contraction was distinctly lower in decentralized bladder preparations than in controls. Decentralized detrusor muscle (10 weeks) showed no increased response to α‐adrenoceptor stimulation (phenylephrine, clonidine, noradrenaline), but the sensitivity to carbachol (at 3 and 10 weeks) was significantly decreased compared with controls. The release of [3H]noradrenaline was decreased by carbachol 10‐7to 10‐5both in controls and in decentralized (10 weeks) detrusor muscle, the decrease being significantly more pronounced in the decentralized group at carbachol concentrations of 10‐7and 10‐6. There were no differences between controls and decentralized bladders of muscarinic receptor concentration, but decentralization significantly reduced the affinity for the radioligand used to label the receptors.Thus, the main changes caused by parasympathetic decentralization of the feline bladder seem to be a reduced post‐junctional, but an increased prejunctional response to muscarinic re

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09038.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Intestinal tissue from cats was homogenized and fractionated by ultrafiltration to a molecular range of about 500‐10,000 and separated by gel chromatography. The fractions from the gel filtrations were tested with regard to their ability to inhibit Na,K‐ATPase as assayed with ρ‐nitrophenylphosphate. The fractions that inhibited Na,K‐ATPase were pooled and named pooled fraction 2. Pooled fraction 1 contained molecules larger, and pooled fraction 3 and 4 the molecules smaller, than pooled fraction 2. The four fractions were assayed for natriuretic ‘activity’ on anaesthetized rats. Administering pooled fraction 3 (no Na,K‐ATPase‐inhibiting activity) i.v. augmented renal excretion of sodium and water, whereas the other pooled fractions did not exhibit any consistent natriuretic effect. Cardiac ventricular tissue from cats was fractionated in the same manner as was done for the intestine. None of the cardiac fractions contained any natriuretic material. It is proposed that the cat small intestine contains a na

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09039.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Na,K+‐ATPase activity is decreased in homogenized renal tissue from GM‐treated rats. This study examines whether the site of the active effect of GM on Na,K‐ATPase activity in the kidney can be localized to the proximal convoluted tubules (PCT) where the drug is taken up and where it will produce necrosis.In rats treated with gentamicin (50 μg. kg‐1.day‐1i.m.) for 7 days, PCT Na,K‐ATPase activity was reduced as compared to vehicle‐treated rats but returned to control levels 7 days after treatment withdrawal. In another nephron segment, the medullary thick ascending limb of Henle (mTAL), where GM induced lesions are uncommon, Na,K‐ATPase activity was the same in GM‐ and vehicle‐treated rats treatment. To study thein vitroeffect of GM, dissected PCT and mTAL segments from untreated rats were preincubated for 30 min with GM 10‐3m, a dose similar to the tissue concentration in chronically treated rats. In tubule segments that were permeabilized to allow the drug to enter the cells, GM 10‐3msignificantly inhibited Na,K‐ATPase activity both in PCT and mTAL. In non‐permeabilized mTAL segments GM did not inhibit Na,K‐ATPase activity. GM inhibition of Na,K‐ATPase activity in permeabilized PCT segments persisted after the tubules were rinsed in GM free medium. GM does not inhibit Na,K‐ATPase partly purified from the renal cortex. Conclusion. Gentamicin inhibits Na,K‐ATPase activity in renal tubule cells when it has access to the cytoplasm. Treatment with GM will therefore cause a selective inhibition of Na,K

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09040.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The central cardiovascular responses induced by neuropeptide Y (0.25 nmol) and adrenaline (2.00 nmol) given i.c.v. in close to maximal doses in the awake, unrestrained male rat were studied following changes in the pituitary‐adrenal activity. Adrenalectomy (1 week) alone significantly reduced the vasodepressor response to i.c.v. adrenaline but not to i.c.v. neuropeptide Y. Corticosterone replacement treatment (5 mg kg‐1x 2, i.p., 1 week) significantly reduced both the maximal (peak) and overall (area) vasodepressor responses to i.c.v. adrenaline and neuropeptide Y (only overall responses) in the adrenalectomized rat. Corticosterone treatment alone in the sham‐operated rat highly significantly reduced the vasodepressor responses to both i.c.v. adrenaline and neuropeptide Y. The bradycardic action of centrally administered neuropeptide Y was no longer significant after alterations in pituitary‐adrenal activity.The present results suggest that corticosterone treatment can abolish the centrally evoked vasodepressor responses to close to maximal doses of adrenaline and neuropeptide Y, which may contribute to their hypertensive properties in man. Finally, after adrenalectomy the central vasodepressor responses to neuropeptide Y dominate, since the adrenergic vasodepressor responses are selectively reduced. This dominance is reduced by corticosterone replacement treatment. The results indicate an antagonistic role of adrenocortical steroids in control of centrally induced acute vasodepressor responses to neuropeptide Y and adr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09041.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The present study documents daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit in the rat. One‐hundred and twenty‐five Sprague‐Dawley rats were used. They were bred under a cycle of 12 h light/12 h dark starting at 07.00 h. Fifty‐three rats were decapitated between 09.00 and 16.00 h (study I) and 72 rats in groups of six were decapitated at 2‐h intervals for a period of 24 h (study II). In study I, plasma atrial natriuretic peptide was 156±11 pg mg‐1(mean ± SEM). In study II, atrial natriuretic peptide was at a control level from 08.00 to 18.00 h and then began to increase. At 22.00 h, atrial nartriuretic peptide was 420 ± 105 pg ml‐1, which was significantly higher than at 08.00 h (P<0.05). The serum osmolality was over 300 mosmol kg‐1during the day. The highest mean osmolalities (315, 317, 312 mosmol kg‐1were found from 18.00 to 22.00 h. These were significantly different (P<0.05) from other groups during the day. The haematocrit was highest at 14.00 h (49.5 ± 0.7%) and lowest at 24.00 h (43.6 ± 0.8%) (P<0.05).In conclusion, we have shown that there are significant daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit during a 24‐h period and 12 h light/12

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09042.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Intravital microscopy of rabbit tenuissimus muscle was used for studies of endogenous nitric oxide as a microvascular regulatorin vivo.Derivatives of were administered in order to modulate the formation of nitric oxide from L‐arginine. Nw‐nitro‐L‐arginine methylester (L‐NAME) (1‐100 mg kg‐1i.v.) dose‐dependently reduced microvascular diameters. A concomitant blood pressure increase and a decrease in heart rate was observed. The blood pressure increase induced by L‐NAME (30 mg kg‐1) was reversed by L‐arginine (1 g kg‐1) but not D‐arginine. Vasodilation in response to topical acetylcholine (0.03‐3 μM) was significantly inhibited by L‐NAME (30 mg kg‐l), whereas vasodilation by sodium nitroprusside (300 nM) was not affected. Vasomotor nerveinduced vasodilatation, induced by stimulation of the tenuissimus nerve after neuromuscular blockade by pancuronium in animals pretreated with guanethidine, was significantly attenuated by L‐NAME, an effect also reversed by L‐arginine. The vasodilatation in response to active contractions of the muscle induced by motor nerve stimulation as well as the vasodilator response elicited by graded perfusion pressure reductions were unaffected by L‐NAME or NG‐monomethyl‐L‐arginine (L‐NMMA, 10‐4M) administered topically.Our results indicate that endogenous nitric oxide formed from L‐arginine is a modulator of microvascular tonein vivo.Furthermore, the results suggest that endogenous nitric oxide is required for vasomotor nerve‐induced vasodilatation, whereas it does not appear to play a role in myogenic va

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09043.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

The effect of intrathecally applied tachykinin antagonist D‐NicLys1, 3‐Pal3, D‐Cl2Phe5, Ama6, Trp7,8, Nle11‐substance P, spantide II, on the long‐term increase of spinal cord excitability after activation of unmyelinated muscle afferents was studied in decerebrate, spinalized, unanaesthetized rats. A conditioning stimulus train (1 Hz, 20 s) that activated unmyelinated fibres in the gastrocnemius muscle nerve facilitated the flexor reflex for about 1 h, which was strongly blocked by pretreatment with spantide II (3 µg). The present results indicate that the facilitation of the flexor reflex by conditioning stimulation of a muscle nerve is mediated by tachykinins and possibly other neuropeptides which may be released from the central terminals of these unmyelinated

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09044.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In order to examine the relation between mechanical alternans and associated electrical alternans during acute myocardial ischaemia, we determined the effect of a ventricular premature beat and calcium antagonists on mechanical and electrical alternans during acute coronary occlusion in anaesthetized dogs. Isometric contractions and unipolar electrocardiograms were recorded from ischaemic myocardium. During coronary occlusion, mechanical alternans was accompanied by electrical alternans, which was an alternate change in the ST segment elevation, i.e. the higher ST and the lower ST. Electrical alternans was frequently discordant and in some cases accompanied by discordant mechanical alternans. Both discordant electrical and mechanical alternans became concordant and were potentiated after the ventricular premature beat. In all cases, concordant mechanical alternans was accompanied by concordant electrical alternans and vice versa. In this situation, the higher and the lower ST corresponded to the larger and the smaller contractions respectively. Thus, a fixed correspondence was observed between mechanical and electrical alternans. A fixed correspondence was also observed between mechanical alternans and the variation in the time taken for repolarization of the monophasic action potential. Verapamil and diltiazem inhibited both electrical and mechanical alternans. The present results support the idea that a common mechanism, such as a beat‐to‐beat cycle of the transmembrane and intracellular movement of calcium ions, may play a role in the mechanisms of electrical and mechanical altern

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09045.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

This study examines the influence of renal nerves on the development of renovascular hypertension in proximal aortic constricted rats. The rats were studied 1 week after unilateral or bilateral denervation of the renal artery. Denervation had no effect on the increase in mean arterial pressure induced by the constriction. The glomerular filtration rate and filtration fraction in control and in proximal aortic constricted rats were not influenced by the denervation. The Na excretion was increased in the denervated kidney both in control and in proximal aortic constricted rats. Plasma angiotensin II levels were not different from controls in innervated or unilaterally denervated proximal aortic constricted rats. In bilaterally denervated proximal aortic constricted rats the plasma angiotensin II levels were significantly higher. The renovascular hypertension and the alteration in renal function in proximal aortic constricted rats are not dependent on renal nerve activity.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1991.tb09046.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY