bluuebunny/crossref_metadata_2025 huggingface dataset:
Release of endothelin‐like immunoreactivity in relation to neuropeptide Y and catecholamines during endotoxin shock and asphyxia in the pig
Authors: PERNOW J. , HEMSEN A. , HALLEN A. , LUNDBERG J. M.
Published: December 2008

The changes in endothelin‐like immunoreactivity in plasma during various provocations in the pig were investigated and related to those of neuropeptide Y, noradrenaline and adrenaline. Release as revealed by overflow was determined in the spleen, kidney and femoral vascular bed (skeletal muscle) simultaneously by collecting local venous and arterial blood samples. Under basal conditions there was no net release of endothelin‐like immunoreactivity from any region but a net removal (negative overflow) over the kidney. Endotoxin administration (20 μgkg‐1h‐1for 4 h) increased arterial endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity, noradrenaline and adrenaline seven‐, 27–, 100– and 166‐fold respectively, as well as splenic and renal vascular resistance. An increased overflow of endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity and noradrenaline, indicating local release, was observed in the spleen during endotoxin administration. The arterial plasma endothelin‐like immunoreactivity during endotoxaemia correlated significantly with the splenic and renal vasoconstriction (r =0.75 and 0.68 respectively). Chromatographic characterization revealed that the main portions of arterial plasma endothelin‐like immunoreactivity collected during endotoxaemia corresponded to synthetic endothelin‐1 and big endothelin. A similar uptake (50–90%) and plasma half‐life (1–2 min) of exogenous endothelin‐L‐like immunoreactivity was observed both under control conditions and after endotoxin, suggesting that elevated plasma endothelin‐like immunoreactivity after endotoxin was the result not of reduced clearance but rather of enhanced release. Asphyxia for 2 min did not increase arterial endothelin‐like immunoreactivity but evoked an increased overflow of endothelin‐like immunoreactivity, neuropeptide Y‐like immunoreactivity and noradrenaline as well as vasoconstriction in the spleen. Capsaicin induced a release of neuropeptide Y‐like immunoreactivity and noradrenaline from both the spleen and the kidney and of adrenaline from the adrenal, but no detectable overflow of endothelin‐like immunoreactivity from any of the vascular regions. Renal nerve stimulation, renal artery occlusion for 30 min, haemorrhagic shock, hypotension induced by nitroprusside infusion or serotonin did not cause any detectable increase in arterial plasma levels or local overflow of endothelin‐like immunoreactivity.

It is concluded that plasma levels of endothelin‐like immunoreactivity are increased, suggesting release in the pig in response to endotoxin administration and asphyxia. The possible involvement of endothelin as a mediator of the peripheral vasoconstrictor responses during these situations remains to be further established.
On‐line electrochemical monitoring of the local noradrenaline release evoked by electrical stimulation of the sympathetic nerves in isolated rat tail artery
Authors: MERMET C. , GONON F. G. , STJÄRNE L.
Published: December 2008

A treated carbon fibre electrode was used to measure by differential normal pulse voltammetry or differential pulse amperometry the release of noradrenaline from the sympathetic nerve terminals innervating the smooth muscle in rat tail artery. On calibrationin vitrowith exogenous noradrenaline in phosphate‐buffered saline solution the electrode recorded an oxidation current at +0.1 V, the oxidation potential of noradrenaline. This signal was proportional to the noradrenaline concentration in the solution. When the electrode was apposed to the wall of the artery there was no oxidation current at +0.1 V under resting conditions, but electrical nerve stimulation for 1–100 s at 1–10 Hz induced a current with a peak at this potential. This signal was suppressed by tetrodotoxin, guanethidine or cadmium, or by omission of calcium; it was strongly enhanced by tetraethylammonium and potentiated by the noradrenaline uptake blockers desipramine or cocaine. The results indicate that the carbon fibre electrode method described here may be used to monitor on‐line the nerve stimulation‐induced increase in the local noradrenaline concentration at the surface of the muscle layer in a blood vessel such as the rat tail artery.
Effect of cooling on smooth muscle response to 5‐hydroxytryptamine in human hand veins
Authors: BODELSSON M. , ARNEKLO‐NOBIN B. , TORNEBRANDT K.
Published: December 2008

5‐Hydroxytryptamine has been suggested to be a mediator in peripheral cold‐induced vasospasm. In order to investigate the contribution of different 5‐hydroxytryptamine receptor subtypes in the contractile response during cooling, segments of subcutaneous hand veins obtained from 50 patients undergoing hand surgery were examinedin vitroin organ baths. The temperature in the bath was initially 37 ±C and was either continuously lowered to 10 ±C or kept constant at 37 ±C, 29 ±C or 20 ±C. Cooling to 25 ±C augmented the contractile response to 5‐hydroxytryptamine in intact as well as in endothelium‐denuded segments. The 5‐hydroxytryptamine2receptor antagonist ketanserin antagonized the contractile response to 5‐hydroxytryptamine at 37 “C, and in addition abolished the cold‐induced enhancement of the response during cooling. This points to a major role of the 5‐hydroxytryptamine2receptor in the cold‐induced augmentation of the response to 5‐hydroxytryptamine2which was further supported by increased contractions to the 5‐hydroxytryptamine2receptor agonist α‐methyl‐5‐hydroxytryptamine during cooling. Contractile responses were also obtained by the selective 5‐hydroxytryptamine1‐like receptor agonist GR43175 interpreted to indicate the presence of a smaller 5‐hydroxytryptamine1‐like receptor population. However, the response to GR43175 was unaffected by cooling. These results warrant further investigations of the role of 5‐hydroxytryptamine in cold‐induced peripheral vasospasm.
Neurally evoked responses of rat mesenteric resistance arteries are dependent on intracellular release of calcium
Authors: NIELSEN H. , MULVANY M. J.
Published: December 2008

Rat mesenteric resistance arteries (diameter < 250 μm) were isolated and mounted in a myograph, and experiments were designed to test whether neurally evoked responses of these vessels are dependent on intracellular release of calcium. The responses to nerve stimulation were completely abolished in calcium‐free media, and the possible contribution of intracellular release of calcium could therefore not be examined by switching to a calcium‐free solution, Instead, the vessels were stimulated intermittently for 5 s at intervals of 90 s. Following 5 s of nerve stimulation, the intracellular calcium stores were depleted by application of 25 mM caffeine for 15 s. Vessels were then bathed in calcium‐free saline, and subsequently 2.5 mM Ca2+was replaced at varying times prior to nerve stimulation. With 5 s allowed for calcium repletion, the response to nerve stimulation was significantly smaller than the nerve response after 40 s in calcium‐containing saline. The results suggest that the response to nerve stimulation is dependent on the time allowed for the intracellular store to refill, implying that intracellular release of calcium is a critical determinant of the neurogenic response in resistance arteries.
Neurophysiological evidence for and characterization of the post‐ganglionic innervation of the adrenal gland in the rat
Authors: CARLSSON S. , SKARPHEDINSSON J. O. , JENNISCHE E. , DELLE M. , THORÉN P.
Published: December 2008

The aim of this study was to examine and characterize the post‐ganglionic innervation of the adrenal gland, using a neurophysiological nerve recording technique.

Adrenal multifibre nerve activity was recorded in chloralose‐anaesthetized Wistar rats. To test for post‐ganglionic nerve activity, trimethaphan, a ganglionic blocker, was given intravenously. About 60% of the adrenal nerve preparations tested responded with a marked decrease in nerve activity (to 52 ± 11% of pre‐trimethaphan activity, P < 0.01), while other nerves responded with an increase in activity (to 152 ± 29% of pre‐trimethaphan activity, P < 0.01). Based on these responses, the nerves were considered to contain predominantly post‐ or preganglionic fibres respectively, and the difference in response to an intravenous injection of trimethaphan between the two groups was significant (P < 0.01).

It was also demonstrated that the post‐ganglionic adrenal nerve activity had a greater variability in firing pattern than preganglionic adrenal nerve activity. We also examined whether there was any cardiac rhythmicity in the investigated nerves. There was a weak cardiac rhythmicity in six out of 12 post‐ganglionic adrenal nerves, but there was no cardiac rhythmicity in the remaining six post‐ganglionic nerves, and we observed no cardiac rhythmicity in preganglionic nerves. In contrast, renal sympathetic nerves showed a profound cardiac rhythmicity.

Our results might explain recent histological findings of a direct post‐ganglionic innervation of the adrenal cortex. We speculate that this nerve population is involved in steroid synthesis indirectly via regulation of the cortical blood flow or directly via a direct innervation of parenchymal cells in the adrenal cortex.
Electric muscle stimulation in the spontaneously hypertensive rat induces a post‐stimulatory reduction in activity: role of different opioid receptors
Authors: HOFFMANN P. , SKARPHEDINSSON J. O. , THORÉN P.
Published: December 2008

We have previously shown that prolonged low‐frequency muscle stimulation, inducing contractions of the gastrocnemius muscle, in conscious spontaneously hypertensive rats leads to an opioid‐mediated post‐stimulatory reduction in blood pressure and analgesia. In the present study we investigated whether muscle stimulation would also induce a post‐stimulatory reduction in behavioural activity in the spontaneously hypertensive rats. Selective opioid receptor antagonists were used to analyse the involvement of endogenous opioids.

Muscle stimulation, lasting 60 min, induced a post‐stimulatory sedation that outlasted the stimulation for hours. Sniffing, locomotor activity and total behavioural activity were significantly reduced. The post‐stimulatory reduction in activity was reversed back to control levels by a high dose of naloxone (15 mg kg‐1i.v.). The selective μreceptor antagonist, β‐funaltrexamine, given intracerebroventricularly before stimulation, did not influence the development of the post‐stimulatory drop in activity. The δ‐receptor antagonist ICI 154,129 had no effect at all on the already developed sedation, whereas MR 2266 BS, a k‐receptor antagonist (3 mg kg‐1i.v.), completely reversed the drop in activity.

These results show that muscle stimulation gives rise to an opioid‐mediated post‐stimulatory reduction in activity in spontaneously hypertensive rats. The results also indicate the involvement of the opioid k‐receptor in the behavioural response.
Effects of growth hormone on muscle regeneration and IGF‐I concentration in old rats
Authors: ULLMAN M. , ULLMAN A. , SOMMERLAND H. , SKOTTNER A. , OLDFORS A.
Published: December 2008

A study was made of regeneration of skeletal muscle in young adult and old rats and of the effects of administration of growth hormone to old rats. Regeneration was achieved by subjecting the right extensor digitorum longus muscle to ischaemic necrosis. The level of insulin‐like growth factor I in serum was markedly decreased in old rats of 27 months of age compared with young adult rats aged 6 months. Daily injections of 4 IE recombinant human growth hormone during the 10 weeks of regeneration increased the level of insulin like growth factor I to almost the same levels as in rats aged 6 months. The body weight increased by 13% in the old rats treated with recombinant human growth hormone, while the weight of the untreated old rats was constant. The regenerating right and the normal left extensor digitorum longus muscles were studied 10 weeks after the ischaemic necrosis. The absolute and relative weights of regenerating muscle were decreased in 27‐month‐old rats compared with the rats aged 6 months. No significant difference between normal old rats and old rats treated with recombinant human growth hormone was observed either in muscle weight or in maximum contraction force. The results show that old rats have reduced levels of circulating insulin‐like growth factor I. Administration of recombinant human growth hormone raises the level of insulin‐like growth factor I to that of young adult rats, and causes an increased body weight. Muscle regeneration after ischaemic necrosis is impaired in old rats apparently by the formation of large amounts of connective tissue. Supplementation with growth hormone does not reverse this impairment.
Effects of eccentric and concentric resistance training on skeletal muscle substrates, enzyme activities and capillary supply
Authors: TESCH P. A. , THORSSON A. , COLLIANDER E. B.
Published: December 2008

This study compared the skeletal muscle metabolic adaptations in response to combined eccentric and concentric or concentric resistance training regimens. Twenty‐six physically active males were assigned to either the combined eccentric and concentric group (n= 10), the concentric group (n=10) or the control group (n = 6). The combined eccentric and concentric and the concentric groups performed four to five sets of maximal, voluntary bilateral quadriceps muscle actions at 1.05 rad s‐l using a speed‐controlled dynamometer three times per week for 12 weeks. The concentric group performed 12 concentric actions per set, whereas the combined eccentric and concentric group performed six coupled eccentric and concentric actions per set. Bilateral percutaneous muscle biopsies were obtained from m. vastus lateralis at rest pre‐ and post‐training. Tissue samples were analysed for contents of adenosine triphosphate, creatine phosphate and creatine and for enzyme activities of citrate synthase, lactate dehydrogenase, myokinase, phosphofructokinase, hexokinase and Mg2+‐ATPase using fluorometric techniques. Histochemical staining procedures were employed to determine capillary supply. The overall increase (P < 0.05) in muscle strength was greater (P < 0.05) for the combined eccentric and concentric group than for the concentric group. Enzyme or substrate contents and capillary supply were unaltered after either type of training. It is suggested that substantial increases in muscle strength may occur in response to resistance training without enhancing or compromising metabolic function of skeletal muscle.
Increased negativity of interstitial fluid pressure contributes to development of oedema in rat skin following application of xylene
Authors: RODT S. Å. , WIIG H. , REED R. K.
Published: December 2008

Intradermal interstitial fluid pressure (p1) has been studied in rat skin during formation of inflammatory oedema caused by application of xylene.P, was measured with sharpened micropipettes connected to a servocontrolled counter‐pressure system. Control p1averaged –1.3 + 0.6 (SD) mmHg. Following xylene application p1decreased to – 5.0 mmHg after 5 min and then increased to stabilize at about 0 mmHg at 45–60 min and later. When the transvascular fluid shifts accompanying the inflammatory reaction were prevented by inducing circulatory arrest prior to xylene application, p1fell to –7.5 mmHg within 5 min and remained at this level throughout the observation period of 90 min. Aprotinin in large doses (80,000 KIE kg‐1) before xylene application reduced the fall in Pi, whereas indomethacin had no effect. The increased negativity inP1will add directly to a normal transcapillary net filtration pressure of about 0.5 mmHg, resulting in a 10– to 20‐fold increase in this pressure. The present experiments therefore suggest that the interstitium plays an active role in oedema formation in the initial phase of xylene‐induced inflammation in rat skin through the development of an increased negativity ofPi.
Effect of menthol on the bladder cooling reflex in the cat
Authors: LINDSTRÖM S. , MAZIÈRES L.
Published: December 2008

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 mm solution 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 walls.
Effects of parasympathetic decentralization on some nerve‐mediated functions in the feline urinary bladder
Authors: ANDERSSON K.‐E. , ATTA M. A. , ELBADAWI A. , LARSSON B. , MATTIASSON A. , SJÖGREN C.
Published: December 2008

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 10‐7 to 10‐5 both in controls and in decentralized (10 weeks) detrusor muscle, the decrease being significantly more pronounced in the decentralized group at carbachol concentrations of 10‐7 and 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 receptor stimulation.
Tachykinns mediate changes in spinal reflexes after activation of unmyelinated muscle afferents in the rat
Authors: WIESENFELD‐HALLIN Z. , XU X.‐J. , HÅKANSON R. , FENG D.‐M. , FOLKERS K.
Published: December 2008

The effect of intrathecally applied tachykinin antagonist D‐NicLys1, 3‐Pal3, D‐Cl2 Phe5, 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 afferents.
Renal nerve activity does not contribute to the development of renovascular hypertension in rats with abdominal aortic constriction
Authors: EKLÖF A.‐C. , HÖKFELT T. , APERIA A.
Published: December 2008

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.
Calcitonin treatment of immobilization osteoporosis in rats
Authors: TUUKKANEN J. , JALOVAARA P. , VÄÄNÄNEN K.
Published: December 2008

We studied changes in bone mass induced by immobilization and the ability of salmon calcitonin to inhibit immobilization osteoporosis in rat. The bone mass of the immobilized hind leg of rat was compared with the contralateral non‐treated leg. Neurectomy and cast immobilization reduced the bone mineral mass to an equal extent. However, the dose‐response of calcitonin was different with these immobilization techniques. Calcitonin 15 IU kg‐1 administered once daily reduced bone ash weight difference significantly after 2 weeks' neurectomy (P < 0.001). This had no significant effect on the bone loss induced by cast immobilization, but the dose had to be delivered as two injections given every 12 h. Two weeks' immobilization decreased the incorporation of 45Ca into bones. Calcitonin could not prevent this. However, calcitonin tended to inhibit the overall incorporation of 45Ca into bones in immobilized rats but yet had no effect on 45Ca incorporation in non‐immobilized rats.

Immobilization decreased serum alkaline phosphatase activity in cast‐immobilized animals. Neurectomy did not change serum alkaline phosphatase activity from a sham operation level. The tartrate‐resistant acid phosphatase to total acid phosphatase ratio in the serum increased significantly in neurectomized rats and in cast‐immobilized calcitonin‐treated rats.
Responses to eccentric and concentric resistance training in females and males
Authors: COLLIANDER E. B. , TESCH P. A.
Published: December 2008

The adaptive responses to 12 weeks of accommodated resistance training were compared in females (n= 11) and males (n= 11). They performed four to five sets of six maximum bilateral coupled concentric and eccentric quadriceps muscle actions at 1.05 rad s‐1 three times per week. Uni‐ and bilateral concentric and eccentric peak torque at different angular velocities (0.52, 1.57 and 2.62 rad s‐1), three repetition maximum half‐squat and vertical jump height were measured before and after training.

Both groups displayed marked increases (P < 0.05) in concentric and eccentric peak torque at all angular velocities. The relative increases (P < 0.05) in unilateral concentric (26 vs. 26%) and eccentric (28 vs. 36%) peak torque across speeds were similar in females and males. The corresponding increases (P < 0.05) in bilateral concentric and eccentric peak torque across speeds were 20 vs. 28% and 24 vs. 39% respectively. The three repetition maximum half‐squat (20 vs. 25%) and vertical jump height (10 vs. 8%) increased (P < 0.05) equally in females and males.

These results suggest that the overall increases in concentric and eccentric peak torque and functional strength, in response to short‐term accommodated resistance training, occur at a rate that is independent of sex. The torque‐velocity relationship, however, appears to change in males suggesting a relatively greater enhancement of maximum voluntary force in the slow‐speed, high‐force region.
Response of capsaicin pretreated skin blood vessels to exercise
Authors: KUROZAWA Y. , NASU Y. , NOSE T.
Published: December 2008

Six normal men performed cycle ergometer exercise from 50 W to 125 W in a room maintained at 26 d̀C. Capsaicin was introduced by iontophoresis into the forearm skin. Forearm skin blood flow (FSBF) during graded exercises before and after capsaicin treatment was measured by laser Doppler flowmetry. Forearm skin blood flow before capsaicin treatment increased depending on the intensity of exercise. However, forearm skin blood flow 24 hours after capsaicin treatment scarcely increased during graded exercise. The cause of this capsaicin effect was discussed.
Edrophonium chloride for testing colonic contractile activity in man
Authors: BASSOTTI G. , IMBIMBO B. P. , BETTI C. , ERBELLA G. S. , PELLI M. A. , MORELLI A.
Published: December 2008

The effects of cholinergic stimulation on the entire human colon are at present relatively unknown. For this reason, we evaluated the influence of a short‐lived anticholinesterase agent, edrophonium chloride, on proximal and distal colonic contractile activity in man. Eight healthy volunteers of both sexes were studied with a multilumen manometric probe positioned with the aid of a colonoscope. Recordings were then obtained 30 minutes pre‐ and post‐drug administration. Edrophonium chloride (10 mg intravenous) significantly stimulated both proximal and distal colonic contractile activity, and the maximum increase was observed within 10 minutes following injection, although some differences were observed between colonic segments in response to the drug. No important side effects were complained of after edrophonium. Due to the potent stimulatory property on colonic smooth muscle, to its short duration of action, and to the paucity of side effects, it is concluded that edrophonium chloride may be useful as a stimulating substance during manometric investigations of the human colon.
Thyrotropin‐releasing hormone has stimulatory effects on ventilation in humans
Authors: NINK M. , KRAUSE U. , LEHNERT H. , HEUBERGER W. , HUBER I. , SCHULZ R. , HOMMEL G. , BEYER J.
Published: December 2008

Thyrotropin‐releasing hormone (TRH) stimulates pituitary thyrotropine synthesis and release and also regulates autonomic nervous system functions by acting as a neuromodulator and neurotransmitter. In experimental animals a stimulation of ventilation by thyrotropin‐releasing hormone was shown when applied at central nervous system sites that affect respiratory motor output. It was the goal of our study to investigate the respiratory properties of thyrotropin‐releasing hormone on basal and stimulated (i. e. CO2‐rebreathing) conditions following systemic thyrotropin‐releasing hormone application in healthy humans. Thyrotropin‐releasing hormone (200 μg, 400 μg intravenous) initiated a rapid short lasting rise of minute volume, ventilatory airflow and alveolar oxygen tension under steady state breathing (P < 0.001). Breathing frequency was less affected, heart rate rose concomitantly (P < 0.001). While breathing with increasing concentrations of carbon dioxide, minute volume was higher under thyrotropin‐releasing hormone than under placebo alone. Further effects (e. g. nausea, dizziness, palpitations) mostly appeared later than respiratory changes and thus may not be responsible for their initiation.

Our findings prove systemic thyrotropin‐releasing hormone to be a strong respiratory stimulant in man. Response in respiratory output was also accompanied by central nervous system‐effects (e. g. dizziness, restlessness, augmented vigilance). The mode of thyrotropin‐releasing hormone effects on respiration after peripheral administration is still speculative. An augmented sympathetic output or a direct receptor mediated action at central nervous system sites may be responsible, while a peripheral effect cannot be excluded.
Carbohydrate ingestion during prolonged running exercise results in an increase of serum Cortisol and decrease of gonadotrophins
Authors: VASANKARI T. J. , KUJALA U. M. , VILJANEN T. T. , HUHTANIEMI I. T.
Published: December 2008

We tested the hypothesis that improved availability of energy through carbohydrate ingestion could counteract the documented suppression of pituitary‐gonadal function during prolonged exercise. Nine trained males repeated twice a 36 kilometre running exercise with two weeks interval. During the tests the subjects ingested in a randomized single‐blind fashion a total of 1050 millilitres of carbohydrate and placebo solutions. The total amount of ingested carbohydrate was 105 grammes. Venous blood samples were taken before the exercise (sample A), immediately after exercise (B), and 2 hours later (C). In the B samples plasma glucose was 14% higher (P < 0.01) and serum Cortisol 13% higher (P < 0.05) in the carbohydrate than in the control trial. In contrast, the level of LH was 18% (P < 0.05) and that of FSH 11 % lower (P < 0.05) in the carbohydrate than in the placebo trial. Serum testosterone concentration did not differ between the treatment groups. We conclude that carbohydrate ingestion does not counteract the exercise‐associated suppression of gonadotrophin secretion, but results in paradoxical increase of serum Cortisol and decrease of LH and FSH, in comparison to placebo‐treated controls. The higher Cortisol level in carbohydrate group may be secondary to higher insulin levels.
Mechanical properties of isolated human oesophageal submucosal veins
Authors: MADSEN G. , TØTTRUP A. , FORMAN A. , ANDERSSON K.‐E.
Published: December 2008

The mechanical properties of isolated human oesophageal submucosal veins were investigated. The veins were without tone or spontaneous activity and possessed a high compliance, tolerating a stretch of several hundred per cent of the length at which the vessels were first able to contract with only minor increases in passive tension. The veins were capable of producing active tension when the length exceeded 30% of L0 (the length at which maximum wall tension (T0) was developed when activated by 124 mM K+‐solution). The veins from the oesophageal body (OB) had a higher L0 than the veins from the gastrooesophageal junction (GOJ) (1180/μm vs 820 μm) and T0 was correspondingly higher (1.1 mN/mm vs. 0.6 mN/mm). However, there was no significant difference in the calculated effective transmural pressure (P) at the two locations. Noradrenaline induced contractions in all preparations tested with a maximum response equivalent to the tension achieved after stimulation with 124 mM K+‐solution. pD2 values for noradrenaline in vessels from the oesophageal body and the gastrooesophogeal junction were 7.03 pL 0.28 (mean pL SEM) and 7.15 pL 0.20, respectively. The present model seems suitable for future studies of human oesophageal submucosal veins from the oesophageal body and the eastrooesonhaeeal junction.
Left ventricular responses to experimental aortic coarctation in growing puppies
Authors: LESKINEN M.
Published: December 2008

The haemodynamic status of 8 coarctated and 7 sham‐operated beagle puppies was studied by a catheterization technique at rest and during isoproterenol and volume loading at the ages of 7 (I) and 9 (II) months (5 and 7 months after the experimental coarctation).

Proximal aortic systolic and pulse pressures were constantly higher in the coarctation group than in the control group (P < 0.05), and the systolic pressure gradient across the coarctation was always significantly higher in the coarctation group [I at rest mean 45 pL 5 (SD) vs 5 pL 4 mmHg, P < 0.001, and after I isoproterenol infusion 56 pL 9 vs 10 pL 6 mmHg, P < 0.001, and after I dextran infusion 58 pL 10 vs 8 pL 7 mmHg, P < 0.001]. The time constant of exponential isovolumic left ventricular pressure fall after the isoproterenol tests was longer in the coarctation group (I 28 pL 8 ms and II, 30 pL 4 ms) than in the control group (I, 21 pL 2, P < 0.05 and II, 19 pL 3 ms, P < 0.005), indicating impaired relaxation. The tension time index during the volume loading tests increased in the coarctation dogs (I, 4150 pL 660 and II, 4080 pL 810 mmHg s min‐1) to higher levels than in the control group (I, 3550 pL 220, II, 2540 pL 1140 mmHg s min‐1, P < 0.05 both). Cardiac output, left ventricular end diastolic pressure, inotropic parameters and heart rate were similar in both groups during the infusions.

The results show that the hearts of the young animals exposed to chronic pressure load by aortic coarctation maintained their pump performance well. The changes in left ventricular relaxation may be an early sign of impaired diastolic function.
Lack of effects of handling habituation and swimming stress on ethanol‐induced motor impairment and GABAAreceptor function
Authors: TUOMINEN K. , KORPI E. R.
Published: December 2008

The effects of handling habituation and swimming stress on ethanol‐induced motor impairment and the GABAAreceptor function were studied in adult male Wistar rats. Daily handling for 3 to 5 weeks had no significant effect on ethanol‐induced motor impairment in the tilting plane test or on the activity of the rats in the elevated plus‐maze test of anxiety. Plasma corticosterone concentrations were greatly elevated by the tilting plane test procedure, irrespective of handling habituation. Acute, 10‐min swimming stress at + 25 d̀C produced an elevated plasma corticosterone concentration comparable to that produced by the tilting plane test, again irrespective of handling habituation. In cerebrocortical homogenates, short‐term swimming stress had no statistically significant effect on the muscimol stimulation of the GABAAreceptor‐mediated36Cl‐flux in handled and non‐handled animals. Thus, handling habituation and stress had only minor effects on the activity of the central GABAergic systems in acute tests at behavioural and biochemical levels.
Neuropeptide Y (NPY): a vasoconstrictor in the eye, brain and other tissues in the rabbit
Authors: NILSSON S. F. E.
Published: December 2008

The effect of neuropeptide Y (NPY) on uveal vascular resistance was studied in rabbits by direct determination of uveal blood flow from a cannulated vortex vein. Regional blood flows, in the eye, the brain and several other tissues, were measured, with radioactive microspheres, during neuropeptide Y‐infusion in rabbits with and without α‐adrenoceptor blockade.

Intravenous infusion of increasing doses of neuropeptide Y caused a dose‐dependent increase in the total uveal vascular resistance. Maximal effect, a 70% increase, was achieved with 120 pmol kg‐1 min‐1. In the microsphere experiments, this dose rate was given i.v. over 10 minutes and blood flow determinations were made before and at 2 and 10 minutes after the start of the infusion. After 2 minutes of neuropeptide Y, there were marked blood flow reductions in the spleen, kidneys, adrenal glands, gastro‐intestinal tract, choroid plexus and pineal and pituitary gland. The effect in the eye was small at 2 minutes, but at 10 minutes local blood flows in the choroid and the ciliary body were decreased by 50% and the iridal blood flow by 30%. Retinal blood flow was not affected by neuropeptide Y. At 10 minutes there were also significant blood flow reductions in the brain, tongue, masseter muscle and several glandular tissues. The effects of neuropeptide Y on local blood flow in rabbits that had been subjected to α‐adrenoceptor blockade were very similar to the effects in the animals without α‐adrenoceptor blockade.

The results show that, in the rabbit, neuropeptide Y has marked effects on local blood flows in several tissues, including the eye, and suggest that neuropeptide Y may significantly contribute to the uveal vasoconstriction during sympathetic nerve stimulation.
Oedema‐preventing mechanisms in a low‐compliant tissue: studies on the rat tail
Authors: AARLI V. , AUKLAND K.
Published: December 2008

The long‐term effect of elevated tail venous pressure (Pv) on interstitial fluid pressure (Pi) and colloid osmotic pressure (COPi) was studied in rats. Measurements were performed on different rats after 1–5 days of congestion, and on a sham operated control group. Two different degrees of venous stasis were obtained by means of graded ligation of tail veins and skin. Moderate degree of ligation (group 1) caused no visual oedema. More extensive ligation (group 2) gave marked oedema already on day 1 and further progression and exudation from the skin during the following 3 days. Tail venous pressure was measured by micropuncture and interstitial fluid pressure by the wick‐in‐needle technique. Interstitial fluid was sampled by a dry wick method, and colloid osmotic pressure was measured with a membrane osmometer.

In group 1, Pv had increased from 6.5 to 21.5 mmHg on day 1, and thereafter remained unchanged. Interstitial fluid pressure increased from 3.4 to 16.9 mmHg after ligation and to 19.2 mmHg on day 1. Colloid osmotic pressure fell from 11.7 to 5.8 mmHg. From day 1, both interstitial fluid pressure and colloid osmotic pressure remained largely unchanged.

In group 2 rats, tail venous pressure increased to 33.0 and 36.3 mmHg on day 1 and 2 and then fell towards control level during the following 3 days. Interstitial fluid pressure increased to 22.9 and 31.4 mmHg before a rapid decline towards control level. Colloid osmotic pressure was reduced from 11.7 to 5.6 mmHg.

We conclude that hydrostatic counterpressure may provide an oedema‐preventing effect of up to about 15 mmHg. Greater acute increase of interstitial fluid pressure lead to exudation and pressure fall. Reduction of colloid osmotic pressure contributed 6–7 mmHg already on day 1.
Glucose and ketone body turnover in fasting grey seal pups
Authors: Nordøy E. S. , Blix A. S.
Published: December 2008

Concentration and metabolic replacement (turnover) rate of glucose and ketone bodies were determined at intervals during a 52 day postweaning fast in five grey seal (Halichoerus grypus) pups, using bolus injections of radiotracers. Blood glucose was maintained at a high level throughout the fast, while β‐hydroxybutyrate increased 26 times from day 3 to day 37, whereafter it by and large was maintained. Glucose replacement rate decreased to 56% of the day 9 value at day 37 and dropped further to only 32% of the day 9 level at day 52 in two seals, while in another 2 seals it increased at this late stage. The average ketone body replacement rate ranged between 8.6 and 13.8 μmol min‐1 kg‐1, but did not change significantly (P > 0.05) during the fasting period. These results suggest a reduced gluconeogenesis from protein and increased production of ketone bodies, which may in part replace glucose as energy source during fasting.
Potassium homeostasis during and following exhaustive submaximal static handgrip contractions
Authors: BYSTRÖM S. , SJØGAARD G.
Published: December 2008

The aim of the present study was to follow local potassium homeostasis during and after exhaustive contractions. Eight subjects performed static handgrip with their right forearm at 10% 25% and 40% maximal voluntary contraction. Blood flow (venous occlusion plethysmography) and the venous effluent plasma potassium concentration were followed during the contractions and during a 60‐min recovery period. Electro‐myography was registered during exercise (frequency analysis). With all three protocols the blood flow increased significantly during the contractions and the same was true of the effluent plasma potassium concentrations. In the recovery period blood flow and the venous effluent plasma potassium concentration returned to base values within 30 min following 40% maximal voluntary contraction while following 10% and 25% maximal voluntary contraction, venous effluent plasma potassium concentration was still significantly below resting values one hour after the exercise had ceased, indicating a long‐lasting uptake of potassium from the blood into the muscles. In line with this a significant potassium deficit was still seen after 1 hour of recovery following 10% and 25% maximal voluntary contraction. It is concluded that the recovery of potassium homeostasis following prolonged low‐intensity contractions is a slow process. This may be due to either sequestration of potassium in other tissues with a subsequent slow release and/or insufficient sodium/potassium pump activation. The contraction induced potassium loss may play a major role in muscle performance since it may impair mechanical force production, and it is hypothesized that this may be the origin of low‐frequency fatigue.
Influence of some α2‐‐receptor agonists and antagonists on the excitatory non‐adrenergic, non‐cholinergic neurotransmission in the airways of guinea‐pigs in vivo
Authors: JACOBSSON L. , GRUNDSTRÖM N. , ANDERSSON R. G. G.
Published: December 2008

Neural control of smooth muscle tension in the airways of guinea‐pigs can be subdivided into at least four components: an excitatory cholinergic, an inhibitory noradrenergic, an excitatory non‐adrenergic, non‐cholinergic and an inhibitory non‐adrenergic, non‐cholinergíc component. The existence of α2‐adrenoceptors that modulate the excitatory non‐adrenergic, non‐cholinergic nerve activity has also been demonstrated. The aim of the present study was to investigate the dose‐dependence of the selective α2‐receptor agonists UK 14,304, dexmedetomidine and clonidine on these α2‐adrenoceptors in the airway of guinea‐pigs in vivo.

Electrical stimulation of the cervical vagus nerves in anaesthetized guinea‐pigs resulted in a biphasic response in insulllation pressure: an immediate increase due to excitation of cholinergic nerve fibres and a slower, longer‐lasting increase due to activation of the excitatory non‐adrenergic, non‐cholinergic fibres to be studied. The cholinergic compound was abolished by atropine, leaving the excitatory non‐adrenergic, non‐cholinergic component as the sole response recorded during vagal stimulation.

UK 14,304 and dexmedetomidine attenuated the response in a dose‐dependent manner, whereas the effect of the partial agonist clonidine was less dose‐related. UK 14,304 and dexmedetomidine reduced the insufflation pressure about 60 and 53% respectively at the highest dose.

In conclusion, the neurotransmission in the excitatory non‐adrenergic, non‐cholinergic nerves is attenuated by selective α2‐receptors in a dose‐dependent manner. The present study adds support to earlier observations that the excitatory non‐adrenergic, non‐cholinergic neural system in the airways of guinea‐pigs is modulated by α2‐adrenoceptors.
Burst firing of mesencephalic dopamine neurons is inhibited by somatodendritic application of kynurenate
Authors: CHARLETY P. J. , GRENHOFF J. , CHERGUI K. , CHAPELLE B. De La , BUDA M. , SVENSSON T. H. , CHOUVET G.
Published: December 2008

Midbrain dopamine neurons of the zona compacta substantia nigra (SN) and ventral tegmental area (VTA), giving rise to the nigrostriatal and mesolimbocortical midbrain dopamine pathways, respectively, typically display a spontaneous activity consisting of single spikes and bursts. Previously, intracerebroventricular administration of the excitatory amino acid (EAA) antagonist kynurenate has been shown to inhibit burst firing and induce a regular, pacemaker‐like firing of ventral tegmental area midbrain dopamine neurons. In the present experiments, zona compacta substantia nigra and ventral tegmental area midbrain dopamine neurons were recorded in the chloral hydrate anaesthetized male rat. Kynurenate was administered locally, either by micro‐iontophoresis or by pneumatic (micropressure) ejection. Both forms of local kynurenate application produced an immediate inhibition of burst firing and a slightly increased regularity of firing in both zona compacta substantia nigra and ventral tegmental area midbrain dopamine neurons. The present results indicate that excitatory amino acid nerves tonically modulate midbrain dopamine neuronal burst firing directly on the midbrain dopamine cell bodies, further stressing the importance of excitatory amino acid innervation in the physiological function of midbrain dopamine neurons, particularly in the dynamic aspects involved in the behavioural modulation and pharmacological responses of these psychopharmacologically important neurons.
Interaction between antisecretory opioid and sympathetic mechanisms in the rat small intestine
Authors: SJÖQVIST A.
Published: December 2008

The putative existence of an endogenous opioid antisecretory mechanism in the small intestine was tested in anaesthetized Sprague‐Dawley rats. Cholera secretion was elicited with cholera toxin and net fluid secretion was measuredin vivausing a gravimetric technique allowing on line registrations. Opioid blockade with naloxone (10 mg kg‐1i.v.) increased the cholera secretion significantly but had no effect on control absorption. Pretreatment with phentolamine (2 mg kg‐1i.v.) eliminated the effect of opioid blockade indicating an interaction between the opioid and the adrenergic mechanisms. The effect of naloxone on cholera secretion was unchanged after acute division of the sympathetic nerves to the intestine and removal of the adrenals. Chronic sympathetic denervation of the small intestine, on the other hand, abolished the effect of opiate blockade on the secretion. The antisecretory effect of sympathetic nerve stimulation was unchanged by opiate blockade. Conclusion: An intrinsic antisecretory opioid mechanism has been demonstrated in the small intestine of the rat. This endogenous opioid mechanism seems to decrease secretion indirectly via peripheral activation of the sympathetic antisecretory system.
Methylene blue attenuates vasodilatation and enhances vasoconstriction in response to endothelin‐1 in the pig nasal mucosa
Authors: AUBERSON S. , LACROIX J. S. , MOREL D. R. , LEHMANN W. , LUNDBERG J. M.
Published: December 2008

In thiopentone anaesthetized pigs (n= 10), simultaneous recordings of the vasomotor response to local intra‐arterial infusion of endothelin‐1 and ‐3 were performed in three different vascular compartments of the nasal mucosa. Sphenopalatine artery blood flow (reflecting nasal blood flow), nasal cavity volume (representing blood content in capacitance vessels) and laser Doppler flowmeter signal (reflecting superficial mucosal blood flow) increased in response to low doses (4 times 10‐9 to 4 × 10‐8 moles) of endothelin‐1. In contrast, marked vasoconstriction (up to 50% of arterial blood flow reduction) occurred upon higher doses (4 × 10‐7 to 4 × 10‐6 moles). Endothelin‐3 (4 × 10‐9 to 4 × 10‐6 moles) evoked at the highest dose a long‐lasting increase of systemic arterial blood pressure resulting in a 22 × 4% increase in nasal vascular resistance. After local intra‐arterial pretreatment with methylene blue (4 × 10‐4 mol), the vasodilatory responses to low doses of endothelin‐1 were abolished for the three vascular parameters studied, whereas the vasoconstrictor responses in resistance and capacitance vessels evoked by higher doses of endothelin‐1 were increased. In contrast, the laser Doppler flowmeter signal reduction in response to endothelin‐1 was markedly attenuated. The vasodilatatory effect of substance P was abolished after methylene blue probably due to interference with effects of endothelium dependent relaxing factor (EDRF). These observations suggest that in the pig nasal mucosa in uivo, exogenous endothelin‐1 induces a dose‐dependent reduction of blood flow in resistance and capacitance vessels and in superficial mucosa. The vasodilatation observed in response to low doses of endothelin‐1 seems to be sensitive to methylene blue and similar to the effect for substance P, suggesting involvement of EDRF production.