摘要:

The dose‐dependent effects of systemically and locally administered phencyclidine (PCP) on the extracellular levels of dopamine, dihydroxyphenylacetate (DOPAC), homovanillate (HVA), 5‐hydroxyindolacetate (5‐HIAA), γ‐aminobutyrate (GABA), glutamate and aspartate in the dorsolateral striatum of anaesthetized rats were studied byin vivomicrodialysis. Both local (1, 5, 50 and 100 µM) and systemic (2 and 10 mg kg‐1i.p.) PCP caused a dose‐dependent increase in the extracellular levels of dopamine. The lowest PCP doses caused only a moderate but long‐lasting increase in the extracellular levels of dopamine, while the highest PCP doses caused a massive but transient increase followed by a rebound decrease. The low doses of both systemic and local PCP tended to increase the levels of DOPAC, while those of HVA were not changed. The extracellular levels of 5‐HIAA were increased only by the lowest (1 µM) locally administered dose of PCP. GABA levels were increased when PCP was administered locally at two doses. None of the treatments affected the extracellular levels of glutamate and aspartate. The results show that the effects of local and systemic PCP administration are dissimilar on the extracellular levels of 5‐HIAA and GABA and thus provide new information on the neuroche

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09667.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Isometric force, action potentials and in voltage‐clamp1st (second inward current) and its current voltage relation were recorded in papillary muscles from guinea‐pigs and from guinea‐pig isolated ventricular myocytes (35–37oC, 0.5‐1 Hz). Rolipram (1–100 µM) had no significant effect on peak isometric twitch. The rate of rise of force and time to peak tension (TPT) was likewise unaffected. Time to half relaxation (THR) was increased in a dose‐dependent manner and at 30 µM THR was prolonged by 25.3 ± 6% (n= 10,P<0.001). The effect of 30µM rolipram on isometric force was frequency dependent. At 0.25 Hz peak force was increased by 6.3 ± 3.1% (n= 7,P<0.05). At 2 Hz rolipram exhibited a negative inotropic effect of 9.8 ± 3.3% (n= 5,P<0.02). Action potential duration at 90% repolarization was prolonged by 13 ± 6 ms (n= 7,P<0.05), and there was usually no effect on resting potential or action potential amplitude. Sometimes, however, a depressed plateau was recorded. Rolipram was without effect onI1stand its current‐voltage relations. Time to full mechanical restitution after a test interval was not changed but the shape of the restitution curve was altered. The restitution process was much slower in the presence of rolipram. Hence, peak force was lower at test intervals shorter than 800 ms. Likewise, the shape of the curve relating postextrasystolic potentiation to test interval was altered by rolipram. The interval required for maximum potentiation was increased by rolipram and did not significantly affect the recirculation fractio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09668.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Isometric force, action potential and current‐voltage relation were studied in guinea‐pig and ferret papillary muscles. Milrinone (1 μu) increased peak twitch force by 40 + 4%, reduced time to peak tension (TPT) by 12.1 ± 3% (n= 6,P<0.01) and reduced time to half relaxation by 17.3 ± 4.1 % (n= 6,P<0.01). The effect of milrinone was potentiated by rolipram, a RI‐PDE inhibitor which in itself had no inotropic effect. After the addition of rolipram peak isometric force was increased by 104 + 8% (n= 6,P<0.001), TPT was further reduced whereas time to half relaxation was slightly increased after the addition of rolipram. Action potential duration at 75% repolarization was decreased by 11 + 5 ms (n= 6,P<0.05). Milrinone also potentiated the second inward current (Ist) by 21 + 3.2% (n= 6,P<0.01). Peak twitch force in response to a test stimulus after an interval, i.e. mechanical restitution was increased at all intervals. The onset of restitution was faster and time to full restitution also shortened. Maximum postextrasystolic potentiation was greater in the presence of milrinone, whereas relative potentiation was smaller in presence of milrinone (46 ± 7%) than in control (74 ± 7%). The recirculation fraction of activator calcium was enhanced by milrinone from 0.35 ± 0.04 to 0.48 ± 0.07. The results support the view that the positive inotropic effect of milrinone is due to a greater inflow of calcium during the action potential and a more efficient intracellular calcium handling. In addition, the effect on mechanical restitution would suggest a more direct action on sarcoplasmic reticulum calc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09669.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Initial and late effects by adrenergic and muscarinic agonists on inositol (1,4,5) trisphosphate (IP3) and cyclic nucleotide levels were determined and correlated to mechanical response in perfused rat hearts. Forty‐three rat hearts were perfused with Krebs‐Henseleit buffer in a modified Langendorff apparatus as a working preparation. The hearts were perfused as controls (n= 11), or with noradrenaline (10‐6mol 1‐1) (n= 21), or with carbachol (3 × 10‐7mol 1‐1) (n= 11) added to the perfusion buffer. The hearts were frozen at 20 s, 30 s and 40 min after addition of noradrenaline and at 20 s and 40 min after addition of carbachol, and after 5 and 45 min of control perfusion. cAMP and cGMP were determined by radioligand methods and IP3by a combined fast performance liquid chromatography (FPLC) ‐ isotachophoretic method. cAMP increased by 36% within 20 s followed by a decrease (22%) during the 10 s following noradrenaline addition. After 40 min cAMP regained its value near that of 20 s. Noradrenaline perfusion did not influence IP3levels during the first 30 s although the value at 40 min was significantly higher (59%). IP3increased (42%) after 20 s of carbachol perfusion followed by a 25 % decrease at 40 min.Sustained stimulation of β‐receptors (after 40 min in our model) resulted in a repeated increase in cAMP only, without an increase in contractility. Muscarinic receptor stimulation resulted in an early increase in IP3content without a change in mechanical function whereas a‐adrenergic stimulation resulted in only a late increase in IP3content of isolated whole hearts still without any alterati

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09670.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of long‐term endurance exercise on the contractile properties of single skinned muscle fibres from adult rats, were investigated. Adult (4‐month‐old) male rats were subjected to a 16‐week, high‐intensity endurance swimming programme, where animals carried a load (corresponding to 2% of body wt), during all 2‐h training sessions. At the conclusion of the training period, muscle fibres isolated from the extensor digitorum longus (EDL), and soleus (SOL), could be classified into distinct classes or fibre types on the basis of their Ca2+‐ and Sr2+‐activated contractile characteristics. The fast‐twitch EDL comprised two fibre populations, while the slow‐twitch SOL was found to be composed of three distinct fibre types. Endurance swimming modified the contractile characteristics of fibres from both the EDL and SOL, but exerted greater influence on those of the SOL. This was illustrated by significant increases in the sensitivity to Ca2+and Sr2+, and a lower threshold for contraction by these activating ions, in the exercised group. Not one of the total of 272 fibres sampled, exhibited mixed fast‐ and slow‐twitch contractile characteristics, often associated with exercise‐induced fibre type transformations. Thus, high‐intensity endurance swimming induced changes in some single muscle fibre contractile properties of adult rats, but did not cause major changes

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09671.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The visco‐elastic properties of the receptor muscle associated with the rapidly adapting stretch receptor organ of crayfish (Pacifastacus Leniusculus) were studied by recording the tension responses to various length changes. Steady‐state length changes resulted in a non‐linear tension development in the receptor muscle. The tension increased slowly for small extensions and more rapidly when extension increased. Muscle tension responses to ramp‐and‐hold extension were characterized by a transient peak followed by a gradual non‐exponentional decline in tension. At the onset of the ramp the tension increased rapidly, similar to what has been observed in the muscle of the slowly adapting receptor (SM). The steeper rise in tension during the first part of the ramp indicating higher initial stiffness, resulted in a ‘hump’ when large extensions (>15%) were applied. The results show that the rapidly adapting receptor muscle has a more pronounced dynamic component; the ratio between the amplitude of the peak and the steady state response was larger in the rapidly than in the slowly adapting receptor muscle. Accordingly, different values for the elements of a visco‐elastic model of the muscle had to be set for the two types of receptors. The different properties of the rapidly and slowly adapting receptor muscles are in line with the differences in the overall adaptive behaviour of the organ and give further support to the idea that mechanical factors contribute to the ad

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09672.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Small mesenteric arteries from Wistar rats display rhythmic tension oscillations, associated with oscillations in membrane potential, when stimulated with noradrenaline. The purpose of this study was to investigate the role of potassium conductance and Na+, K+‐pump activity in the generation of these oscillations. The effect on the rhythmic contractions of several agents, interacting with K+channels, was studied. Application of apamin, pinacidil or glibenclamide did not affect the rhythmic activity. Tetraethylam‐monium (TEA) increased the frequency of the rhythmic contractions, while application of 4‐aminopyridine (4‐AP) increased the amplitude by approximately 50%, with no changes in frequency. Ba2+, on the other hand, impaired the rhythmic contractions or converted them to irregular oscillations in the presence of functional endothelium, but did not affect oscillations in endothelium‐denuded vessels. Ouabain or exposure to K+‐free solution, procedures known to inhibit the Na+, K+‐pump, abolished the rhythmic contractions. This effect was immediate, suggesting that it was due to elimination of the electrogenic action of the Na+, K+‐ATPase, rather than to a change in intracellular ion concentrations. Exposure to an extracellular potassium concentration of more than 20 mM also inhibited the oscillation activity. The results suggest that the oscillations are not caused by, but may be modulated by, variations in potassium conductance. The Na+, K+‐pump seems to play an important role in the generation of rhythmic contractions

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09673.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Growth of the smooth muscle cells in the rat portal vein was induced by a partial ligation of the vessel. The ligation caused an increase in the transmural pressure and segments of the portal vein were investigated 6 weeks after the ligation. The spontaneous contractile activity of the ligated veins was similar to that of the control veins. In the ligated vessels the active force at optimal length for force development was doubled, 22.8 ± 1.3 compared with 12.5 ± 1.4 mN for the controls. The cross‐sectional area of the media in the ligated veins, determined on transverse sections, increased from the control value of 0.10 + 0.01 to 0.19 ±0.01 mm2. Electron microscopy revealed that the mean cross‐sectional area of the smooth muscle cells in the ligated portal vein was doubled (controls: 6.4 ± 0.6, hypertrophic: 13.6±1.8μm2). This suggests hypertrophy of the smooth muscle cells in the vessel wall as the cause for the increase in cross‐sectional area of the ligated veins. An increase in the number of intermediate filaments was observed in the hypertrophied smooth muscle. The relative contents of contractile (myosin and actin) and structural (desmin and vimentin) proteins were determined with SDS‐polyacrylamide gel electrophoresis. The actin/myosin and vimentin/actin ratios were unaltered by hypertrophy. The hypertrophied veins showed an increase in the desmin/actin ratio (control: 0.20 ± 0.01, hypertrophied: 0.27 ± 0.03). The increased amounts of desmin correlates with the increased number of intermediate filaments observed by electron microscopy. The mechanical and biochemical data indicate a net synthesis of contractile proteins that occurs in proportion to the increa

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09674.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The influence of 10 min intracarotid (i.e.) and intravenous (i.v.) infusions of angiotensin II (Ang II; 20 pmol kg‐1min‐1) on carotid blood pressure (cBP) and renal blood flow (RBF) was studied in unanaesthetized ewes without and with pre‐treatment with the α1‐and β‐adrenoceptor blocker labetalol. RBF was also monitored during 30 min intracerebroventricular (ICV) infusions of Ang II at 2 pmol kg‐1min‐1.The i.e. infusions of Ang II induced about 50 mmHg rise in cBP. A steep decline occurred during 5 min post‐infusion, followed by a much slower reduction with the cBP remaining above control level at 40 min post‐infusion. The pressure elevation induced by i.v. Ang II was less pronounced but exhibited a similar pattern. Labetalol significantly reduced the pressor response to i.e. as well as i.v. Ang II.The i.e. and i.v. infusions of Ang II conspicuously reduced the RBF regardless of whether the ewes were labetalol‐treated or not. At 5 min after the infusions RBF had returned to control level. The ICV infusions did not influence the RBF.Ang II i.e. elicited thirst in 50% of the ewes with the urge to drink remaining at 40 min post‐infusion. The dipsogenic response was not reduced by labetalol pre‐treatment.The results imply that no cerebral component contributes to the reduction in RBF induced by systemic Ang II. However, a centrally mediated action seems to be the cause of the long‐lasting post‐infusion cBP elevation and dipsogenic response. It suggests that, once bound at brain sites, Ang II may have a sustained action, alternatively may initiate cerebr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09675.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The renal hemodynamics were studied in an isolated perfused rat kidney model modified for investigations of the glomerular permeability characteristics. The tubular reabsorptive activity was inhibited by perfusion at low temperature (8oC) in the presence of furosemide and nitroprusside resulting in a dramatic increase in the filtered load of fluid and solute reaching the tubules and hence in tubular pressure. The glomerular filtration rate (GFR), arterial pressure (PA) aid needle pressure (intrarenal tissue pressure,PiR) were continuously recorded and the glomerular hydrostatic pressure was estimated by an arterial occlusion technique.The pre‐ to postglomerular resistance ratio was calculated from the pressure vs. GFR relationships for two perfusates having differing oncotic pressures (π=5.5 and 77 = 20 mmHg), from which estimations of glomerular hydrostatic pressures (PGC) were concomitantly made. Thus, increases inAncould be exactly counterbalanced by equally large increases inPacfor any given GFR, the needle and Bowman's capsule pressures being dependent on GFR but not on plasma colloid oncotic pressure.The experimental interventions resulted in a pronounced elevation ofPiRas compared within vivoconditions, while thePGCvalues were in a normal range, resulting in reduced glomerular filtration pressures. Furthermore, the clearance of albumin varied with the oncotic pressure in agreement with the notion of heteroporosi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1994.tb09676.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY