bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal overflow of noradrenaline and dopamine to plasma during hindquarter compression and thoracic inferior vena cava obstruction in the dog
Authors: BRADLEY T. , HJEMDAHL P.
Published: December 2008

Efferent renal nerve activity was assessed by measurements of the overflow of endogenous noradrenaline (NA) and dopamine (DA) to plasma in the kidney. To obtain correct estimates of the renal contribution to the renal venous outflow of NA and DA, corrections for the renal extraction of catecholamines in arterial plasma were performed by use of tracer amounts of [3H]NA. Hindquarter compression (previously known to cause a neurogenically mediated blood pressure elevation) increased the concentrations of NA, adrenaline and DA in arterial and renal venous plasma. The renal overflow of NA increased from 83.7 ± 32.0 to 361.3 ± 119.4 pmol min_1(P< 0.05) during hindquarter compression. When compared to the renal NA overflow during electrical renal nerve stimulation, this corresponds to an increase in average renal nerve impulse activity from approximately 0.4 to 1.6 Hz. Hindquarter compression also increased the renal overflow of DA to plasma. When venous return to the heart was reduced by obstruction of the thoracic inferior vena cava, the mean arterial blood pressure fell and all catecholamines in plasma increased gradually during the first 10 min of obstruction. The renal overflow of NA was only slightly increased, indicating a minor increase in renal nerve activity. The overflow of DA to plasma was not altered by obstruction of the thoracic inferior vena cava. Neither maneouvre substantially altered the DA/NA ratio for renal overflow rates or for renal venous plasma concentrations indicating that there was no preferential activation of either noradrenergic or putative dopaminergic nerve fibres.
Interstitial compliance and transcapillary fluid balance in renal hypertensive rats
Authors: WIIG H. , REED R. K.
Published: December 2008

Local interstitial fluid volume (IFV) and pressure (IFP) were used to estimate interstitial compliance (=ΔAIFV/ΔIFP) in skin and skeletal muscle of normotensive (NT) and renal hypertensive rats (HT). The IFV was measured as the extravascular 51Cr‐EDTA space, and IFP with micropipettes (tip diameter 2–4 μm) connected to a servocontrolled counter‐pressure system. After control measurements, overhydration was induced by infusion of saline, 10% of body weight i.v. with or without venous stasis. Alternatively, dehydration was induced by peritoneal dialysis with 20% glucose or by furosemide infusion with or without 24 h fluid deprivation. Control ECV averaged 24.94 and 24.73 ml Per 100 8 in NT and HT, respectively (P > 0.05). Control PV averaged 2.81 and 3.28 ml per 100 g in NT and HT, respectively (P= 0.061), and control IFP was more positive in HT than in NT: 0.4 mmHg in skin (P < 0.05) and 0.2 mmHg in skeletal muscle (P > 0.05). Dehydration changed PV significantly more in HT than in NT (P < 0.05). The interstitial volume‐pressure curve was linear in dehydration and the initial part of overhydration but gradually levelled off, and the maximal rise in IFP was 1–1.5 mmHg in skin and muscle. Interstitial compliance was calculated from the dehydration part of the volume‐pressure curve and was in NT 14% per mmHg both in skin and skeletal muscle. In HT, compliance during dehydration was 10.2 and 20.7% reduction in IFV per mmHg fall in IFP in skin and muscle, respectively, not significantly different from corresponding values in NT (P > 0.05). We conclude that HT had unaltered ECV and a tendency to higher PV, and that interstitial compliance was not significantly different in normotensive and hypertensive rats.,
Sympathetic nerve activation decreases the release of vasoactive intestinal polypeptide from the feline intestine
Authors: SJÖQVIST A. , FAHRENKRUG J.
Published: December 2008

The splanchnic nerves to the small intestine were stimulated in anaesthetized cats. Activation of the sympathetic nerves caused vasoconstriction, increased net fluid absorption and decreased release of vasoactive intestinal polypeptide (VIP) in the small intestine. In the colon, parasympathetic nerve stimulation elicited vasodilatation and increased release of VIP. Additional stimulation of the sympathetic lumbar colonic nerves decreased the colonic blood flow and inhibited the release of VIP. These effects of the stimulation of the lumbar colonic nerves were blocked by phentolamine. It is concluded that, in the feline intestine, sympathetic nerve stimulation presynaptically decreased the release of VIP via an a‐adrenergic mechanism.
On the patterns of blood pressure, heart rate, and blood levels of noradrenaline and adrenaline during haemorrhage in the rat
Authors: HAGGENDAL J.
Published: December 2008

Mean arterial blood pressure (MAP), heart rate (HR), and blood levels of noradrenaline (NA) and adrenaline (A) were studied in Sprague‐Dawley rats during haemorrhage. The bleeding was performed in different ways towards complete exsanguination or into a reservoir kept at a constant pressure of 35 mmHg. Awake, unstressed rats or rats anaesthetized with different anaesthetics were examined. Four different phases in the reaction patterns were observed during bleeding. The first phase with the parameters studied expected to be at steady state, was found to be very shortlasting. Only very small blood volumes could be drawn without giving signs of interference with sympathetic activity. The second phase with signs of increased sympathetic activity, as increased HR, also was very shortlasting. Thereafter the marked third phase followed with signs of evident sympathetic inhibition, involving marked decreases in MAP, HR, and blood levels of NA. The last period, phase four, showed signs of a second period of increased sympathetic activity with increased HR and blood levels of NA (and A). On bleeding into a reservoir for 4 h signs of all four phases could be observed.
Vagotomy inhibits the effect of neurotensin on gastrointestinal transit in the rat*
Authors: HELLSTRÖM P.M.
Published: December 2008

Neurotensin has previously been shown to delay gastric emptying, gastrointestinal transit and ileo‐caecal emptying in the rat. To investigate the vagal influence on these effects of neurotensin, separate groups of rats were operated with combined vagotomy and pyloroplasty or with pyloroplasty alone and compared to a group of normal rats. All animals were supplied with a permanent gastrointestinal catheter and a venous catheter. After operation the rats were allowed to recover for 7 days, and were fasted for 24 h prior to the experiments. A radioactive marker of 1.0‐0.5mlNa251CrO4in isotonic polyethylene glycol 400 was instilled intraluminally in the stomach, proximal or distal the small intestine. Saline (control animals) or neurotensin (test animals) was given i. v. in each group studied. The animals were killed at 15, 30, 60, and 120 min after administration of the marker. The distribution of the marker in the gastrointestinal tract was registered with a scintillation detector and quantitative analysis of the amount of radioactivity retained in separate gastrointestinal segments was carried out. Gastric emptying was delayed by combined vagotomy and pyloroplasty (P< 0.01) compared to pyloroplasty alone and normals. Neurotensin at doses of 6 (P< 0.05) and 12 (P< 0.01) pmol kg‐1min‐1retarded gastric emptying dose‐dependently in normals and rats with pyloroplasty alone, but did not further slow the the gastric emptying in rats with vagotomy and pyloroplasty. However, at a dose of 24 pmol kg^1min‐‘ neurotensin delayed gastric emptying (P< 0.01) compared to controls. Gastrointestinal transit was slowed down by neurotensin at a dose of 6 pmol kg“1min‐1in normals (P< 0.01) and rats with pyloroplasty alone (P< 0.05). In rats with vagotomy and pyloroplasty, neurotensin at doses of 6 and 12 pmol kg‐1min‐1had no effect on gastrointestinal transit. However, at 24 pmol kg‐1min‐1neurotensin slowed gastrointestinal propulsion. This effect was mostly confined to a delay of gastric emptying (P< 0.01), while the radioactivity of the small intestine was evenly spread out along the gut. A similar pattern was observed in normal animals receiving neurotensin at a dose of 12 pmol kg‐1min‐1. Small intestinal transit was delayed by neurotensin at a dose of 6 pmol kg‐1min‐1in normals (P< 0.01) which was not different from rats with combined vagotomy and pyloroplasty (P< 0.05) and pyloroplasty alone (P< 0.05). Ileocaecal emptying was inhibited by neurotensin at a dose of 6 pmol kg‐1min‐1in normals (P< 0.01) and rats with pyloroplasty alone (P< 0.01). However in animals with combined vagotomy and pyloroplasty neurotensin at the same dose had no effect. The present results indicate that an intact vagal innervation is of importance for the slowing of gastrointestinal transit by neurotensin in the rat.
Blood flow distribution, lymph flow, villus tissue osmolality and fluid and electrolyte transport after exposing the cat small intestine to sodium deoxycholate
Authors: KARLSTRÖM L. , JODAL M. , LUNDGREN O.
Published: December 2008

The effect of luminal perfusion of a dihydroxy bile salt (sodium deoxycholate) on net fluid transport, intestinal haemodynamics, lymph flow, electrolyte transport and villus tissue osmolality was studied in cat jejunum. Furthermore, the effects of hexamethonium and tetrodotoxin, two drugs influencing nervous activity, were investigated. Concomitant to net fluid secretion, the bile salt increased mucosal blood flow whereas capillary filtration coefficient and lymph flow remained unchanged. Net sodium and chloride transport changed from absorption to secretion. The change of sodium transport was due to both an increased flux from tissue to lumen and a reduced flux in the opposite direction. Villus tissue hyperosmolality was reduced. None of the effects on intestinal haemodynamics correlated with the change in net fluid transport. Furthermore, hexamethonium and tetrodotoxin inhibited the secretion of fluid and electrolytes without influencing the induced changes in intestinal haemodynamics. It is concluded that the bile salt induces intestinal fluid secretion by stimulating an active secretory process in the crypts via enteric nerves. A minor part of the total change in net fluid transport may be due to a reduced uptake in the villi.
Quantitative autoradiography of central neurotransmitter receptors: methodological and statistical aspects with special reference to computer‐assisted image analysis
Authors: BENFENATI F. , CIMINO M. , AGNATI L. F. , FUXE K.
Published: December 2008

In the last few years, quantitative receptor autoradiography has been extensively employed to study the distribution and the functional role of area‐specific transmitter receptors in the central nervous system. In the present paper we have developed quantitative methodologies for the analysis of autoradiograms using computerized image analysers coupled with standard TV camera input for the microdensitometrical evaluations. These procedures include the assessment of the film response to radioactivity using appropriate standards calibrated according to brain tissue quenching and non‐linear conversion of density measurements in radioactivity values adopting the best mathematical model fitting to give as little variability as possible in the transformations. The reliability of the proposed approach has also been evaluated by means of a computer‐assisted Monte Carlo simulation and parallel biochemical determinations.
Quantitation of noradrenaline nerve density in mouse iris by computer‐assisted image analysis
Authors: LUTHMAN J. , HALLMAN H.
Published: December 2008

The density of noradrenaline (NA)‐containing nerve fibres in mouse iris was measured with computer‐assisted image analysis techniques both under normal conditions and during regeneration. Noradrenaline nerves were visualized by Falck‐Hillarp formaldehyde condensation technique in whole‐mount spread preparations of mouse irides. The samples were analysed in a fluorescence microscope connected to a commercially available image analysis system (IBAS/Kontron). A software program was developed for specific detection of fluorescence and the nerve density was determined by calculating the area covered by fluorescence in percentage of total measuring field. The method showed good reproducibility as observed both when repeated measurements were performed in the same measuring field or when consecutive measurements on the same set of irides were performed. Also the inter‐assay variation between control values in the different experiments was low. Loading of the adrenergic nerves by incubation in α‐methyl‐NA or conditions leading to partial diffusion of the fluorophore had minor effects on the nerve density values. The regeneration of the NA nerve fibres after a selective toxic sympathectomy with 6‐hydroxydopamine was also studied. The nerve fibre density values measured by image analysis correlated well with the uptake of [3H]NA; the endogenous NA levels recovered much more slowly, however. It thus seems that endogenous transmitter levels might be a somewhat insensitive index of nerve terminal regrowth, at least in early stages of regeneration. The results indicate that image analysis is a powerful tool to quantitate a transmitter‐identified nerve terminal network in a histological preparation.
The effect of inhaled carbon dioxide and hypoxia mixtures on the electrical and mechanical activities of respiratory muscles in dogs
Authors: VILJANEN A. A. , VILJANEN B. , MATTILA S.
Published: December 2008

The effects of hypercapnia and hypoxia on the regulation of breathing was studied in six mongrel dogs during pentobarbital anaesthesia with special reference to their action on the respiratory muscles. Carbon dioxide (5.5 % in air) inhalation produced an increase of minute volume due to augmentation of respiratory frequency and tidal volume. The number of electrical impulses per breath remained unaffected despite the increase tidal volume. Therefore the mechanical ventilation increased more than the electrical output to the respiratory muscles indicating that the efficiency of the muscles increased. The tidal volume increased more than the pressure impulse (mechanical work by the respiratory muscles) suggesting that the airway conductance was increased during hypercapnia. During hypoxic stimulus (11% oxygen in nitrogen) the increase of minute volume was due to increase in respiratory frequency. The ratio of tidal volume to the number of electrical impulses in the respiratory muscles remained unaltered. During combined carbon dioxide and hypoxia stimulus the responses were similar to those of carbon dioxide stimulus alone. However, the increase of minute volume and the increase in the ratio of tidal volume and pressure impulse to the number of electrical impulses in the respiratory muscles were more pronounced. These findings suggest that carbon dioxide affects the regulation of breathing (i) above the respiratory muscles and (ii) in the muscles themselves. Hypoxic stimulus seems not to have any direct effect on the respiratory muscles in dogs during pentobarbital anaesthesia.
The time dependence of training‐induced increase in skeletal muscle capillarization and the spatial capillary to fibre relationship in normal and neovascularized skeletal muscle of rats
Authors: ADOLFSSON J.
Published: December 2008

One hundred and eighty‐four rats of different ages were investigated regarding the basic capillary‐fibre array and the array resulting from capillary proliferation induced by swimming training and dipyridamole treatment. The time dependence of the training‐induced capillary increase in the muscle was also investigated. Sections of the medial portion of the quadriceps femoris muscle were evaluated in light microscope for total capillarization, fibre area and fibre type composition. After 4 and 8 weeks of swimming training, increases in capillary density, capillary to fibre ratio and mean number of capillaries in contact with each fibre were recorded. No changes in muscle fibre area or fibre composition were seen. In all groups the majority of the capillaries was in contact with three muscle fibres. The capillary proliferation induced by training and dipyridamole treatment was confined to the capillaries in contact with two and three fibres. The results indicate a basic hexagonal capillary‐fibre array with a possible position for a capillary in each corner of the hexagon. This pattern is retained in the increased vascularity induced by swimming training and dipyridamole treatment.
Effects of TRH on cerebral and peripheral blood flows; role of submesencephalic brain stem centres
Authors: KOSKINEN L.‐O. D.
Published: December 2008

The localization of the origin of the cardiovascular effects elicited by thyrotropin‐releasing hormone (TRH) was attempted in this study. The radioactively labelled microsphere method was employed for measurement of regional cerebral (rCBF) and peripheral blood flow in albino rabbits anaesthetized with urethane. The effect of 50 μg and 2 mg kg‐1TRH (administered i.v.) on rCBF and peripheral blood flow was evaluated in animals with the brain stem sectioned (BSS) at the level of pons‐mesencephalon. The cerebral vasodilating effect of TRH was abolished or attenuated, while the peripheral vasoconstriction and increase in mean arterial blood pressure (MAP) was unaffected. Cordotomy at the C, level caused a marked fall in MAP and abolished the pressor response to TRH. In animals infused with angiotensin II, in order to normalize the decreased MAP after cordotomy, TRH caused a marked increase in rCBF. Administration of 50 ng and 5 μg TRH into the fourth ventricle caused a marked peripheral vasoconstriction and pressor response. The same amounts of TRH administered into the mesencephalic aqueduct caused a marked increase in rCBF and peripheral vasoconstriction. The results indicate that TRH elicits the pressor and peripheral vasoconstrictor responses from a submesencephalic brain stem region. The increase in rCBF caused by TRH is probably mediated by a somewhat higher submesencephalic level.
Concentration dependence of halide fluxes and selectivity of the anion pathway in toad skin
Authors: HARCK A. F. , LARSEN E. HVIID
Published: December 2008

The isolated toad (Bufo bufd) skin was mounted under voltage‐clamp conditions in a chamber shown to cause no significant edge damage. The serosal side of the skin was bathed with NaCl‐Ringer's, and the passive voltage‐sensitive anion conductance studied in its fully voltage activated state, V =– 80 raV (apical bath negative). The active sodium currents were eliminated by replacing external Na+ with K+. With [Cl‐]0 varying between 1.45 mM and no mM (gluconate substitution) and [I‐]0= 3 mM, the total clamping current (y) and the sum of halide currents (x), estimated from flux measurements, were related by y = 1.0x –3.7 μAcm_2(r2= 0.98, n = 50 preparations). The increase in [Cl‐], produced a sigmoidal increase in Q‐ influx and clamping current, with the rate coefficient for the influx increasing with [Cl_]0 for 1.45 < [Cl‐]0 < 60 mM, but decreasing slightly again as [Cl‐]0 was further raised to uomM. A similar relationship was obtained between the rate coefficient for the Br‐ influx and [Br‐]0, and the I“influx and [Cl‐]0, indicating that these three ions are transported by a pathway that is activated by Cl‐0 and Br‐0. The rate coefficients for the influxes ranked as follows, I‐:Cl‐:Br‐= 0.7:1:1.3. The I‐/C1‐ selectivity was shown to be independent of the degree of Cl”0 activation of the anion pathway, and identical with the I‐/C1‐ selectivity of a furosemide‐sensitive, conductive pathway. With [Cl“]0, [Br_]0, or [I‐]0= 110 mM, the currents ranked as follows, CI‐: Br‐: I”= 1:0.68:0.06, indicating that CI, to a lesser extent Br‐, and I‐, poorly activate the conductive anion pathway. External I“was a potent inhibitor of the Cl‐0 activation of the Cl‐ conductance. The unidirectional I‐fluxes ([I‐]0= [I”]i = 3 mM, [Cl‐]0=[d‐= no mM) revealed passive transport for V <– 50 mV, active transport for V= o mV, and exchange diffusion for V = 50 mV, confirming our previous finding that depending on the transepithelial potential, the toad skin exhibits three modes of anion transport. A model that shares some properties with that of the anion transport system of the red cell membrane accounts for our findings, and for an inwardly directed active CI‐ flux in terms of C1‐/HC07 exchange.
Effect of hypotension induced by sodium nitroprusside on catecholamine overflow in the canine kidney
Authors: BRADLEY T. , SOLLEVI A. , LAGERKRANSER M.
Published: December 2008

The overflows of noradrenaline (NA) and dopamine (DA) to plasma in the kidney in response to hypotension induced by sodium nitroprusside were studied in barbiturate‐anaesthetized dogs in order to evaluate the possible existence of separately regulated renal noradrenergic and dopaminergic nerve fibres. When mean arterial blood pressure was lowered to 55 ± 5 mmHg, arterial plasma NA, DA and adrenaline concentrations were increased and renal blood flow decreased. Renal sympathetic nerve activity was assessed by measuring the renal overflow of catecholamines to plasma. To obtain more accurate estimates of the renal contribution to catecholamines in renal venous plasma we corrected for the renal extraction of arterial catecholamines, assessed by the extraction of endogenous adrenaline. The corrected renal NA overflow to plasma increased from 164 ± 52 to 419 ± 137 pmol min‐1(P< 0.05) during sodium nitroprusside induced hypotension. The renal overflow of DA to plasma was, however, not influenced significantly. The DA/NA ratio for renal venous plasma concentration as well as for renal overflow to plasma was decreased(P <0.05) by sodium nitroprusside induced renal nerve activation. In contrast, electrical renal nerve stimulation has previously been shown to enhance the overflows of DA and NA in parallel. One possible interpretation of these findings is that sodium nitroprusside selectively activated renal noradrenergic but not the putative dopaminergic nerve fibres while electrical stimulation activated both types of fibres.
Cerebral function during hypotensive haemorrhage in spontaneously hypertensive rats and Wistar Kyoto rats
Authors: SKARPHEDINSSON J. O. , STAGE L. , THORÉN P.
Published: December 2008

Studies on cerebral function during cerebral ischaemia are usually performed on conscious animals after ligation of a major vessel supplying the brain. In this work, we studied somatosensory evoked potentials (SEP) in chloralose‐anaesthetized Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) during hypotensive haemorrhage, with the main emphasis on the SHR which are more vulnerable. The main purpose was to see whether haemorrhaged SHR could be used for studies of cerebral function during relative cerebral ischaemia in anaesthetized rats. The mean arterial pressure (MAP) was rapidly lowered to 45–50 mm Hg and maintained at that level by adjustments of bleeding and transfusion. This resulted in pronounced sympathetic inhibition and bradycardia in all rats. In SHR, this sympatho‐inhibitory response was usually reversed after about 20 min. In one group of hypertensive rats (SHRt, n= 24), MAP was raised to 75 mm Hg by partial re‐transfusion, when heart rate (HR) had returned to the pre‐bleeding level and MAP was maintained at that level for the rest of the experiment. All the other rats (SHR, n – 12; WKY, n= 11) were kept at 45–50 mm Hg for 32 min, after which WKY were bled further to a MAP of 30 mm Hg for 8 min. SEP amplitudes decreased after haemorrhage in all groups but more so in SHR. In the WKY group, SEP were only modestly attenuated during the first 32 min, but after further bleeding to 30 mm Hg the amplitudes were reduced to the same extent as in SHR. Some SHR showed flat SEP immediately upon haemorrhage and were excluded from the SHRt group. In the SHRt group, the attenuation of SEP was biphasic; during the first 12 min there was only a modest decrease of amplitudes but after that the attenuation was more rapid and accompanied by an increase in HR and sympathetic nerve activity. After re‐transfusion, SEP amplitudes stabilized at 50–60% of the control level. In agreement with earlier findings, our results show that SHR are more vulnerable than WKY when bled to a pressure of 50 mm Hg. In addition, by carefully manipulating MAP in SHR, we obtained a stable level of attenuated SEP which can be used to study acute impairment of cerebral function due to relative cerebral ischaemia in anaesthetized rats.
Intramuscular pressure, EMG and blood flow during low‐level prolonged static contraction in man
Authors: SJØGAARD G. , KIENS B. , JØRGENSEN K. , SALTIN B.
Published: December 2008

Seven men performed one‐legged isometric knee‐extension at 5% MVC for 1 h. Intramuscular pressure increased with contraction from its resting value of 14 (2–31) mmHg. Some intramuscular pressure recordings stayed at an almost constant level throught the 1 h contraction, but most recordings showed large fluctuations from resting values up to 90 mmHg. The overall mean intramuscular pressure was twice the resting value. In some cases, EMG recordings confirmed that the changes in intramuscular pressure were related to alternating recruitment of various parts of the knee‐extensors. Blood flow in the femoral vein increased within 3 min of 5% MVC to a level of 1.58 (1.25‐2.22) 1 min‐1 and no significant changes occurred during the 1 h contraction. In two subjects blood flow was measured also in the recovery period, and this decreased almost immediately when the muscle relaxed. It is concluded that during low‐level static contractions, the blood supply to the exercising muscle is maintained at a sufficiently high level, and that the alternating recruitment of muscle fibres may result in a heterogeneously distributed blood flow within the contracting muscle. Despite this the muscle was fatigued after the 1 h at 5 % MVC. The rating of perceived exertion (RPE) increased from 1.9 (1–3) at the beginning to 4.5(2–8) at the end of contraction, and MVC was decreased by 12% after the contraction.
Carbonic anhydrase inhibition and cell volume regulation in Necturus gallbladder
Authors: PERSSON B.‐E. , LARSON M.
Published: December 2008

Gallbladder epithelial cells transport salt and water isotonically as the renal proximal tubule. The cells also have the property of regulating their cell volume in response to osmotic stress (Fisher et al. 1981, Persson & Spring 1982, Fisher & Spring 1984, Foskett & Spring 1985). The volume‐regulating phenomenon is the result of a balance between cell uptake of salt and water at the luminal membrane and exit at the basolateral membrane. Different properties regarding volume regulatory increase and decrease have been found (Eriksson & Spring 1982 and Larson & Spring 1983). The present study links fluid transport and volume regulatory increase of the cell. First we concluded from histological techniques that carbonic anhydrase is present in the cell membrane or in the vicinity of the epithelial cells. Then we measured a decreased net fluid transport in the presence of increasing concentrations of the carbonic anhydrase inhibitor acetazolamide. We showed that the volume regulatory increase is substantially slowed down and that the steady‐state volume of the cells changed when carbonic anhydrase was inhibited. Our conclusion is that the rate of CO2 hydration was a limiting step, at carbonic anhydrase inhibition, in both the net transfer of salt and water and also in the ability of the cells to efficiently regulate their volume.
Uptake of dehydroascorbic acid and ascorbic acid to isolated nerve terminals and secretory granules from ox neurohypophyses
Authors: THORN N. A. , NIELSEN F. S. , JEPPESEN C. K. , CHRISTENSEN B. L. , FARVER O.
Published: December 2008

When uptake ofl‐[I4C]ascorbic acid ([14C]AA) to various organs in guinea‐pigs was studied after intracardiac injection, the adenohypophysis, pars intermedia, and the neurohypophysis had an uptake per milligramme protein which was about half of the uptake to the adrenals. Adrenal uptake was 20 ± 2.8 pmol mg‐1protein μCi‐1injected. The uptake to the different parts of the hypophysis was considerably higher than the uptake to pancreas, liver, kidney, spleen and other organs. When isolated nerve endings (neurosecretosomes) from ox neurohypophyses were incubated with a medium containing labelled dehydroascorbic acid ([14C]DHA), the uptake was much slower than when the medium contained labelled ascorbic acid. The uptake of [I4C]DHA showed a linear dependence on concentration, and was not influenced by addition of Mg2+ATP. Addition of Mg2+4‐ ATP, omission of Ca2+Mg2+or exchange of Na+in the medium with K+had no effect on the uptake of ascorbic acid. When isolated secretory granules from ox neurohypophyses were incubated with a medium containing [14C]DHA, uptake was considerably faster than the uptake when they were incubated in a medium containing [I4C]AA. The uptake of dehydroascorbic acid was linear with the concentration in the medium and was not changed by addition of Mg2+ATP. Addition of 10 mM NH4C1 or exchange of 120 mM K+in the incubation medium with Na+did not change the uptake of dehydroascorbic acid. The contents of copper, zinc, iron and cobalt were determined in isolated nerve endings (A) and membranes (B) as well as in lysate (C) from isolated neurosecretory granules. The results (in nmol mg‐1protein) were for Cu: (A): 0.25 ± 0.01 (SEM), (B): 0.67 ± 0.i6, (C): 0.22 ± 0.06; for Zn: (A): 0.53 ± 0.13, (B): 6.97 ± 0.75, (C): 1.8 ± 0.53; and for Fe: (A): 15.6 ± 1.9, (B): 6.92 ± 0.32, (C): 3.15 ± 0.43. In all preparations the cobalt content was below the detection limit (< 5 pmol rag‐1protein).
Release of immunoreactive vasoactive intestinal peptide (VIP) from the gallbladder in response to vagal stimulation
Authors: BJÖRCK S. , FAHRENKRUG J. , JIVEGÅRD L. , SVANVIK J.
Published: December 2008

Immunoreactive VIP was detected in the gallbladder lumen and in the arterial blood and venous effluent from the gallbladder in fasting cats. During perfusion of the gallbladderin vivothere was a constant basal intraluminal secretion of VIP. The VIP concentration in the luminal effluent exceeded that in plasma supporting the notion that there was a release from the gallbladder tissue. The rate of secretion was significantly increased during efferent electrical stimulation of the peripheral cut end of the cervical vagal nerves, after blockade with atropine. A similar increase in concentration of VIP was seen in the venous effluent from the gallbladder. The results suggest a local release of VIP from intrinsic neurons within the gallbladder wall. This release is increased in response to activation of non‐cholinergic fibres in the vagus nerves, suggesting a role for VIP in regulation of gallbladder functions.
Postnatal loss of synaptic terminals in the normal mouse soleus muscle
Authors: FLADBY T.
Published: December 2008

Using conventional physiological techniques for measuring unitary contractions and end‐plate potentials (epps), the number, size and segmental properties of motor units (MUs) in the soleus muscle of the mouse during postnatal development have been examined. The number of MUs remains constant after birth, and there is no evidence of segmental preferences in the innervation pattern, before, during or after the postnatal elimination of redundant terminals. In neonates, MU size estimates based on twitch contractions are 30% smaller than tetanic estimates. Intracellular recording of epps shows that this is caused by facilitation of epps on repetitive stimulation. The frequency of occurrence of epps in the muscle from a few, isolated motor axons shows that the average motoneuron contacts 36% of the fibres in the muscle neonatally. A substantial fraction of the contacts is subthreshold for twitch activation of their fibre. The MU size remains constant up to day 5.During the next ro days, the MU size is reduced to the mature value of 5 % of the fibres in the muscle. It is concluded that the neonatal loss of synaptic terminals in this muscle takes place without concomitant loss of entire motor neurons, and that it is independent of possible segmental preferences in the innervation of the muscle.
Peripheral neural correlates of cutaneous anaesthesia induced by skin cooling in man
Authors: KUNESCH E. , SCHMIDT R. , NORDIN M. , WALLIN U. , HAGBARTH K.‐E.
Published: December 2008

The effect of local skin cooling on the behaviour of low‐ and high‐threshold mechano‐receptive afferents innervating glabrous and non‐glabrous skin was studied in microneurographic recordings on awake human subjects. Cooling with ice or ethyl chloride to a skin surface temperature below 10 °C caused a reduction of receptor sensitivity in 49 out of 52 studied low‐threshold afferents. This effect was reversible upon warming but some reduction often persisted for a few minutes after normal skin temperature had been reached. The subjects' sensations of application and removal of von Frey hair stimuli were more resistant than and reappeared before the sensation of sustained pressure. This could be explained by shorter recovery times for fast than for slowly adapting units and by a relative preservation of the dynamic responses of the slowly adapting units. During the recovery phase some low‐threshold mechanoreceptive afferents exhibited a transient ‘spontaneous’ discharge in the absence of external mechanical stimulation. The suppression of afferent C‐fibre responses to needle strokes was more pronounced and long‐lasting than the effect on A‐fibre responses and largely paralleled the recovery of sensation of pain. It is concluded that the local anaesthetic effect of skin cooling is to a large extent explicable in terms of receptor desensitization although other mechanisms may contribute.
Histamine in the retina
Authors: EHINGER B. , HALLENGREN C.
Published: December 2008

Retina and choroid were rapidly and gently extracted from chickens, guinea‐pigs, rats, rabbits and cows. They were frozen, weighed and pooled in 3 % trichloroacetic acid in a refrigerator. Using a radioenzymic assay, histamine was found to be present in the retina of guinea‐pig (4.26 ± 0.677 nmol g‐1), rabbit (1.08 ± 0.422 nmol g‐1) and cow (0.189 ± 0.036 nmol g‐1), but not detected in chicken and rat. In the choroid, histamine was found in all species except rat (chicken: 4.92 ± 0.542 nmol g‐1; guinea‐pig: 121.5 ± 4.46 nmol g‐1; rabbit: 18.7 ± 3.93 nmol g‐1; cow: 0.36 ± 0.095 nmol g‐1).The study verifies the presence of histamine in the retina of some species, and thereby supports previous fluorometry assays.
Blockade of central β‐adrenoceptors attenuates tremor induced by 5‐hydroxytryptamine (5‐HT)‐receptor activation in rats
Authors: HALLBERG H.
Published: December 2008

The effect of β‐adrenoceptor antagonists, varying in lipophilicity and receptor selectivity, were studied on tremor elicited byl‐5‐hydroxytryptophan (L‐5‐HTP) in rats pretreated with a peripherally acting decarboxylase inhibitor and a monoamine oxidase inhibitor, or by the directly acting 5‐HT agonist s‐methoxy‐N,N‐dimethyltryptamine (5‐MeODMT). Plasma levels of the β‐adrenoceptor antagonists were determined simultaneously. The non‐selective lipophilic adrenoceptor antagonist propranolol was found to dose‐dependently reduce tremor intensity, whereas the non‐selective hydrophilic adrenoceptor antagonist sotalol had no effect, indicating a central site of action. Furthermore, β1‐selective blockade with the adrenoceptor antagonist metoprolol had no effect on tremor intensity, whereas the β2‐selective antagonist ICI 118,551 dose‐dependently suppressed tremor intensity, suggesting that the β‐adrenoceptor subtype involved is of the β2‐type. These results suggest that blockade of centrally located β2‐adrenoceptors are able to attenuate the tremor response following 5‐hydroxytryptamine receptor activation.
Prejunctional β2‐adrenoreceptor blockade reduces nerve stimulation evoked release of endogenous noradrenaline in skeletal musclein situ
Authors: DAHLÖF C. , KAHAN T. , ÅBLAD B.
Published: December 2008

Prejunctional β‐adrenoceptor‐mediated modulation of endogenous noradrenaline (NA) overflow elicited by sympathetic nerve stimulation was studied in blood‐perfused canine gracilis musclein situ.An attempt was made to subclassify these β‐adrenoceptors by comparing the effects of β1‐selective (metoprolol) and non‐selective (propranolol) β‐adrenoceptor blockade. Animals were pre‐treated with desipramine and phenoxybenzamine in order to counteract possible influences of neuronal uptake and stimulation‐evoked changes in vascular resistance on the diffusion of NA into the blood stream. Metoprolol did not decrease stimulation‐evoked NA overflow, as compared with control experiments (−10 and −8 %, respectively). However, propranolol reduced stimulation‐evoked NA overflow by 30% in metoprolol pre‐treated animals (P< 0.05vs.control experiments). Both antagonists elevated basal perfusion pressure, suggesting that vascular post‐junctional β1‐as well as β2‐adrenoceptors are present. Propranolol increased stimulation‐evoked vasoconstriction in metoprolol pre‐treated animals, indicating that neuronally released NA may activate postjunctional β2‐adrenoceptors under these experimental conditions. In conclusion, our findings suggest that NA release can be enhanced by activation of prejunctional β2‐adrenoceptorsin vivo.
Substance P‐induced tachycardia in the anaesthetized rat
Authors: DELBRO D.
Published: December 2008

In pentobarbital‐chloralose‐anaesthetized rats, pretreated with hexamethonium and atropine the mechanism by which substance P (SP) causes tachycardia was analysed. Substance P, when infused i.v. at doses between 0.49 nmol and 1.52 nmol elicited a marked, dose‐dependent tachycardia, which was reduced to less than half by propranolol, 0.1 mg kg‐1. Furthermore, the SP‐induced tachycardia was reduced to about 1/10 of control by guanethidine. Further, the tachycardia, which could also be elicited in pithed rats, was antagonized by the SP‐receptor blocker Spantide, but these results must be taken with care since Spantide itself caused a pronounced and long‐lasting depressor response. It is hypothesized that SP causes tachycardia by exciting specific receptors on the stellate ganglia, which leads to an activation of adrenergic fibres to the sinus node.
Gradation of force output in normal fast and slow muscles of the rat
Authors: HENNIG R. , LØMO T.
Published: December 2008

The discharge patterns of 16 motor units in extensor digitorum longus (EDL) and soleus (SOL) muscles of freely moving adult rats, described by Hennig & Lømo (1985), were further analysed with respect to their role in grading muscle force output. The units fell into three distinct classes, termed EDL‐1, EDL‐2 and SOL‐1, probably corresponding to type FF, FR and S units. The EDL‐1 units generated only single impulses or impulse trains of short duration (phasic firing) which had high frequency and usually started with a short interspike interval (initial doublet). The EDL‐2 and SOL‐1 units generated single impulses and impulse trains of both short and long durations (phasic and tonic firing) without initial doublets. The frequency was high in EDL‐2 and low in SOL‐1 units. In EDL‐2 and SOL‐1 units, the mean durations of the first interspike intervals in a train decreased as the number of impulses per train increased. In EDL‐1 units they did not change. Both SOL and EDL muscles were stimulated through the nerve at different regular frequencies and tension‐frequency (T‐F) curves constructed. The EDL‐2 units fired naturally most often at frequencies corresponding to the steepest part of the EDL T‐F curve. The EDL‐1 and SOL‐1 units fired naturally most often at frequencies where the T‐F curves of their respective muscles began to flaten before maximum tetanic tension was reached. Stimulus trains starting with an initial doublet produced maximum rate of tension development (optimum impulse pattern). At optimum intervals the force increased from about 20 to 85% of maximum tetanic tension when the number of stimuli was increased from 1 to 7. It is concluded that the natural firing pattern of EDL‐1 units and the contractile properties of EDL muscle fibres are normally matched so that the force can develop at maximum rate to maximum levels at the start of contractions. Tension output is apparently regulated primarily through varying number of impulses per train in EDL‐1 units; in SOL‐1 and EDL‐2 units both rate and number of impulses are important.
Late reinnervation of the rat soleus muscle is differentially suppressed by chronic stimulation and by ectopic innervation
Authors: HENNIG R.
Published: December 2008

Soleus (SOL) and extensor digitorum longus (EDL) muscles in adult rats were kept denervated for 2 months by four repeated freezes at 2–week intervals of the sciatic nerve. Reinnervation was studied in the absence or presence of chronic muscle stimulation, starting I month before reinnervation began. In addition, reinnervation was studied in SOL muscles where a previously transplanted fibular (FIB) nerve had formed ectopic neuromuscular junctions outside the original endplate area. After repeated freezes only, reinnervation was complete judged by tension measurements and histochemical examinations in SOL (n= 7) and EDL (n= 8) muscles. In directly stimulated muscles reinnervation was incomplete, and the force tensions evoked from indirect stimulation was on average 87 (n= 5) and 82% (n= 5) of direct muscle stimulation in SOL and EDL muscles, respectively. Of ectopically innervated SOL muscle fibres, only 26% became reinnervated in 12 muscles. Denervation and reinnervation increased the number of muscle fibres in stimulated (n= 4) and unstimulated (n= 5) EDL muscles by 18 and IS%, respectively. In stimulated (n= 4) and unstimulated (n = 7) SOL muscles, on the other hand, the number of muscle fibres remained normal. The stronger suppression of reinnervation in ectopically reinnervated compared to chronically stimulated SOL fibres indicates that reinnervation can also be suppressed by activity independent influences from the foreign nerve.
The accumulation of 2–aminoisobutyric acid in the costal and lumbar parts of the phrenectomized rat diaphragm in vitro
Authors: MAMATAS S. C. , OJA S. S.
Published: December 2008

The accumulation of 2–aminoisobutyric acid initially increased in denervated costal and lumbar parts of the the rat hemidiaphragm after both unilateral and bilateral phrenectomy, followed by a later gradual decrease. The enhancement of accumulation was invariably higher in the costal than in the lumbar part. The accumulation was initially lower in bilaterally than in unilaterally phrenectomized hemidiaphragms, but the relationship was reversed after 72 h due to a faster reattenuation of the enhancements in unilaterally phrenectomized diaphragms.
Effects of splanchnic nerve stimulation and of clonidine on gastric and duodenal HCO‐3secretion in the anaesthetized cat
Authors: FÄNDRIKS L. , JÖNSON C. , NYLANDER O.
Published: December 2008

Experiments were performed on chloralose‐anaesthetized cats with ligated adrenals. The vagal and splanchnic nerves were cut and arranged for peripheral electric stimulation. The gastric lumen was perfused with isotonic saline and gastric H+and HCO3‐secretions were calculated from pH/pCO2measurements in the perfusate. Gastric motility was recorded as changes in hydrostatic pressure in the perfusion circuit. Mucosal HCO3‐secretion into the duodenum was monitoredin situby pH‐stat titration. Vagal stimulation (10 Hz for 10 min) increased gastric and duodenal HCO3‐secretions, as well as gastric motor activity and H+secretion. Splanchnic nerve stimulation (10 Hz for 10 min) did not affect gastric H+and HCO3‐secretions, but tended to decrease gastric motor tone and basal duodenal HCO3‐secretion. Splanchnic nerve stimulation simultaneously with vagal stimulation inhibited gastric contractions and the rise in gastric H+and duodenal HCO3‐secretions observed in response to vagal stimulation alone, but had little effect on the rise in gastric HCO3‐secretion. However, such vago‐splanchnic stimulation in the presence of the α2‐adrenoceptor blocker yohimbine induced gastric contractions, H+secretory and duodenal HCO3‐secretory responses with magnitudes similar to those induced by vagal stimulation alone, whereas the gastric HCO3‐secretory response was larger than by vagal stimulation alone. The α2‐adrenoceptor agonist clonidine (50 μg kg‐1h‐1, i.v.) inhibited the gastric contractions and increases in gastric and duodenal HCO3‐secretion in response to vagal stimulation, but did not influence vagal stimulation of gastric H+secretion. The results suggest the existence of a peripheral sympatho‐inhibitory action on gasmc and duodenal HCO3‐secretion involving α2‐adrenoceptors. Also splanchnic neural stimulatory effects on gastric and duodenal HCO3‐secretion may exist.
Effects of calmodulin antagonists on hormone release and cyclic AMP levels in GH3pituitary cells
Authors: SLETHOLT K. , HAUG E. , GORDELADZE J. , SAND O. , GAUTVIK K. M.
Published: December 2008

In GH, cells the calmodulin antagonists trifluoperazine andN‐(6–aminohexyl)‐I;‐chloro‐1–napthalene sulphonamide hydrochloride (W‐7) showed a dose‐dependent, biphasic effect on the release of growth hormone (GH) and prolactin (PRL). Hormone release was inhibited with 15–30, μm trifluoperazine and with 30–80, μM W‐7, while stimulation was observed with 50–100, μM trifluoperazine and with 150 μM W‐7. Trifluoperazine (≥ 30 μM) and W‐7 (≥ 80 μM) increased the concentration of cellular cyclic AMP. Sulphoxides of trifluoperazine and chlorpromazine (≥ 150 μM) were without effect on hormone release and cellular cyclic AMP. Hydrolysis of cyclic AMP by GH, cytosol was reduced after incubation of intact GH3cells with trifluoperazine (1540 μM). When trifluoperazine was incubated with cytosol, both the high and low affinity forms of cyclic AMP phosphodiesterase were inhibited competitively with calculatedK1of 4.5 and 56 μM, respectively. Stimulation of cyclic AMP phosphodiesterase caused by endogenous calmodulin was blocked by trifluoperazine. Particulate bound adenylyl cyclase activity was inhibited by trifluoperazine, and this effect was counteracted by endogenous calmodulin.
Effects of capsaicin pretreatment on the inflammatory response to scalding injury in the rat
Authors: HAEGERSTRAND A. , DALSGAARD C.‐J. , JONSSON C.‐E.
Published: December 2008

The oedema formation after scalding injury to the rat paw was studied by means of the Evans blue exudation technique. An early and a delayed oedema formation were demonstrated after severe and light scalding, respectively. It was shown that the delayed, but not the early, form was reduced by capsaicin pretreatment, suggesting an involvement of chemosensitive primary sensory neurons in this reaction.