Exercise induces a change in plasma fibrinogen concentration: fact or fiction?

This study examined the effect of exercise on plasma fibrinogen concentrations with simultaneous measurements of plasma volume changes. Eight moderately active males aged 26.6±3.6 years (mean±SD) completed maximal (VO₂max) and submaximal (75% VO₂max for 30 minutes) exercise trials separated by 7 days. Venous blood samples were obtained at rest, immediately postexercise, and following 30 minutes of recovery. Whole blood was analysed for haematocrit and haemoglobin, while citrated plasma was assayed for fibrinogen levels. Values of haematocrit and haemoglobin before and after exercise were utilised for the estimation of plasma volume changes. Plasma volume decreased (p<0.05) immediately following both maximal (−17.7±5.1%) and submaximal (−14.3±4.1%) exercise. Exercise resulted in decreased plasma fibrinogen levels (maximal exercise: from 266.3±14.5 to 222.2±23.9 mg·dL⁻¹; submaximal exercise: from 239.5±45.4 to 209.7±42.4 mg·dL⁻¹) only when postexercise raw data were corrected for the contraction of plasma volume. It is concluded therefore that changes in plasma volume in response to exercise should be taken into account when interpreting exercise effects on plasma fibrinogen concentration.     

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

The objective of this study was to test the hypothesis if thrombolysis induced by recombinant tissue-type plasminogen activator, (rt-PA) could be facilitated by inhibiting carboxypeptidase U (CPU, active Thrombin Activatable Fibrinolysis Inhibitor, TAFIa) activity. The efficacy of rt-PA alone, or in combination with the carboxypeptidase inhibitor MERGETPA, was compared in a dog model of coronary artery thrombosis. Twenty dogs were randomised in two groups, one received rt-PA, 1 mg kg⁻¹, as intravenous infusion over 20 min starting 30 min after thrombus formation, and the other group received rt-PA, 1 mg kg⁻¹, as group one with the addition of MERGEPTA 5 mg kg⁻¹ starting 25 min prior to coronary artery occlusion and followed by infusion of 5 mg kg⁻¹ h⁻¹ until the end of experiment. Efficacy was assessed by determination of time to lysis, duration of patency and blood flow during patency. Both groups had similar baseline characteristics with respect to haemodynamic parameters, i.e., heart rate, blood pressure and coronary artery blood flow. Coadministration of rt-PA and MERGETPA resulted in significant decrease in time to lysis (15±1.5 min vs. 20±1.7 min, p=0.03), increased patency time (87±16 min vs. 46±12 min, p=0.047) and increased coronary blood flow during patency (1131 mL h⁻¹ vs. 405 mL h⁻¹, p=0.015), compared to rt-PA alone. These results indicate that an inhibitor of CPU activity may have a beneficial effect in patients undergoing thrombolytic therapy by attaining shorter time to reperfusion and improved coronary patency.     

Glucocorticoid receptors, fibromyalgia and low back pain

Recently, fibromyaglia (FMS) was shown to be a disorder associated with an altered functioning of the stress response system. FMS patients display a hyperreactive pituitary adrenocorticotropic hormone (ACTH) release in response to corticotropin-releasing hormone (CRH) and to insulin-induced hypoglycemia. We suggested that negative feedback of cortisol could be deranged. Therefore we investigated the properties and function of the glucocorticoid receptors (GR) in FMS patients and compared the results with those of healthy persons and patients with chronic low back pain (LBP a localized pain condition). Forty primary FMS patients (F:M = 36:4), 28 LBP patients (25:3) and 14 (12:2) healthy, sedentary control persons were recruited for the study.

Urinary free cortisol excretion in FMS and LBP patients was lower compared to controls. Only FMS patients displayed lower CBG and basal serum cortisol concentrations when compared to controls. However, plasma free cortisol concentrations were similar in the three groups.

There was no difference in the number of GR per cell among the three groups (FMS: 6498 ± 252, LBP: 6625 ± 284, controls: 6576 ± 304), but the dissociationh constant (K_d) of the FMS (14.5 ± 0.9 nmol/l) and LBP (14.7 ± 13 nmol/l) subjects was significantly higher than that of the controls (10.9 ± 0.8 nmol/l) (p < .05).

The maximal stimulation of the lymphocytes, as measured by the maximal thymidine incorporation (in the absence of cortisol) in the FMS group was approximately 1.5 times higher (p < .05) than in the control or LBP group. The ED₅₀ (the cortisol concentration giving 50% inhibition of the thymidine incorporation), however, was identical in all three groups.

We conclude that FMS patients have a mild hypocortisolemia, increased cortisol feedback resistance in combination probably with a reduced CRH synthesis or release in the hypothalamus. The role of the GR and mineralocorticoid receptor (MR) in the CRH regulation in the FMS patients remains to be solved.     

Halothane's effects on GABA-gated chloride flux in mice selectively bred for sensitivity or resistance to diazepam

The DS (diazepam-sensitive) and DR (diazepam-resistant) lines of mice, selected on the basis of their ataxic response to diazepam, also diverge in the physiologic response of their brain γ-aminobutyric acid_A (GABA_A) receptors to benzodiazepines, as indicated by augmentation of GABA-mediated chloride flux. Cross-sensitivity and -resistance to other sedatives known to interact with the GABA_A-receptor have also been demonstrated in DS and DR mice. Based on the finding that these mice also show cross-sensitivity and -resistance to obtundation by halothane, we predicted that their GABA_A-receptors would also exhibit a differential response to halothane as assayed by an in vitro³⁶Cl⁻ influx assay using purified brain microvesicles. Consistent with this prediction, therapeutic concentrations of halothane enhanced 1 μmol/1 GABA-gated flux with significantly greater potency in DS than in DR mice (halothane EC₅₀ 336±64 μmol/1 (S.E.M.) vs. 605±110 μmol/1, respectively, P = 0.03), but there was no difference in maximal flux enhancement between the two lines (DS 4.7±0.4 nmol·mg⁻¹·3⁻¹, vs. DR 4.7±0.5nmol·mg⁻¹·3s⁻). Halothane (500 μmol/1) also shifted the entire GABA concentration-flux relationship significantly to the left, decreasing the EC₅₀ for GABA in both the DS and DR lines. Importantly, the shift in the GABA concentration-flux response in the presence of halothane was more pronounced in the DS mice (GABA EC₅₀ 1.8±0.4 μmol/1vs.14.7±0.9 μmol/1 without halothane) than in the DR mice (GABA EC₅₀ 4.7±0.6 μmol/1vs.14.7±0.9 μmol/1 without halothane). This effect of halothane was highly significant, both when compared to control, and between the selected lines (P < 0.001). The findings that halothane enhances GABA-gated flux and enhances GABA's channel gating potency support the hypothesis that differential enhancement of agonist-stimulated chloride permeability at GABA_A receptors could be a mechanism underlying the differential obtunding potency of halothane in DS and DR mice. However, at high GABA concentrations halothane decreased maximal chloride flux, more in DS than in DR mice (P < 0.001), which is not consistent with such a mechanism.     

Vasopressin induced cyclooxygenase dependent superoxide generation contributes to K(+) channel function impairment after brain injury

This study determined if vasopressin generates superoxide anion (O⁻₂) in a cyclooxygenase dependent manner and if such production contributes to impairment of dilation to activators of ATP sensitive K⁺ (K_ATP) and calcium sensitive K⁺ (K_ca) channels following fluid percussion brain injury (FPI) in newborn pigs equipped with closed cranial windows. Superoxide dismutase (SOD) inhibitable nitroblue tetrazolium (NBT) reduction was determined as an index of O⁻₂ generation. Under non-brain injury conditions, topical vasopressin (40 pg/ml, the concentration present in CSF following FPI) increased SOD inhibitable NBT reduction from 1±1 to 25±4 pmol/mm². Indomethacin, a cyclooxygenase inhibitor, blunted such NBT reduction (1±1 to 5±1 pmol/mm²), while the vasopressin antagonist, l-(β-mercapto-β β-cyclopentamethylene propionic acid) 2-(o-methyl)-Tyr-AVP (MEAVP) blocked NBT reduction. MEAVP and indomethacin also blunted the NBT reduction observed after FPI. Under non-brain injury conditions, vasopressin (40 pg/ml) coadministered with the K_ATP and K_ca channel agonists, cromakalim and NS1619 (10⁻⁸, 10⁻⁶ M) diminished dilation to these K⁺ channel agonists while indomethacin partially prevented such impairment (13±1 and 23±1 vs. 4±1 and 10±2 vs. 8±1 and 19±1% for cromakalim in untreated, vasopressin, and vasopressin plus indomethacin treated piglets, respectively). Cromakalim and NS1619 induced pial artery dilation was attenuated following FPI, while indomethacin or MEAVP preadministration partially prevented such impairment (13±1 and 23±1, sham control; 1±1 and 4±1, FPI; 8±1 and 16±3%, FPI–indomethacin pretreated for responses to cromakalim 10⁻⁸, 10⁻⁶ M, respectively). These data show that vasopressin increased O⁻₂ production in a cyclooxygenase dependent manner and contributed to this production after FPI. These data also show that vasopressin blunted K_ATP and K_ca channel mediated cerebrovasodilation in a cyclooxygenase dependent manner. These data suggest that vasopressin induced cyclooxygenase dependent O⁻₂ generation contributes to K_ATP and K_ca channel function impairment after FPI.     

The HPA axis response to stress in women: effects of aging and fitness

This study tested the hypotheses that aging is associated with greater hypothalamic-pituitary-adrenal (HPA) axis reactivity to psychological stress, and whether aerobic fitness is associated with a lower HPA axis response to psychological stress. Three groups, consisting of young-unfit women (27.9+/-2.5 yr, n=10), older-unfit women (66.3+/-1.4 yr, n=14), and older-fit women (66.6+/-2.0 yr, n=12), underwent the Matt Stress Reactivity Protocol (MSRP). The MSRP is a stress test battery that combines mental challenges, a physical challenge, and a psychosocial stressor. Definition of fitness was based on maximal oxygen consumption (VO(2max)) where unfit was defined as having VO(2max)average for the respective age group. The MSRP elicited increases in heart rate, blood pressure, ACTH, and cortisol (P<0.001). The older-unfit women had significantly greater cortisol responses to the challenge than both the young-unfit and the older-fit women (P<0.05), who did not differ from each other. ACTH levels were significantly higher in the older-unfit women at baseline and throughout the trial, compared to both young-unfit and the older-fit (P<0.01). The ACTH response was not different between any of the groups. The young-unfit women had greater heart rate responses than the older-unfit (P<0.01), while the latter had greater systolic blood pressure responses (P<0.01). There were no significant differences between the older-unfit and older-fit in terms of heart rate or blood pressure responses. Our result shows that among unfit women, aging is associated with greater HPA axis reactivity to psychological stress, and that higher aerobic fitness among older women can attenuate these age-related changes as indicated by a blunted cortisol response to psychological stress. These findings suggest that exercise training may be an effective way of modifying some of the neuroendocrine changes associated with aging.     

Effect of changes in rate of vascular perfusion on release of substances into the effluent from the brain of the rabbit

The cerebral vasculature of five anaesthetised rabbits was perfused with a perfluorocarbon emulsion via the internal carotid arteries, and the effluent from the jugular veins analysed for ATP, substance P (SP), endothelin (ET) and arginine vasopressin (AVP). Viability of the preparation was monitored periodically by the electrocorticogram, oxygen uptake, carbon dioxide release and perfusion pressure. The basal rate of infusion of 7.8±1.26ml·min⁻¹ resulted in an infusion pressure of 114.0±22.1 mmHg and when increased first to 10.5±1.53ml·min⁻¹ and then to 15.0±1.87ml·min⁻¹, rose to 163.0±33.1mmHg and to 170.0±33.2mmHg, respectively. Between each 3-min period of increased flow the rate was returned to the basal rate for 6 min. of the four vasoactive substances, ET was released at the largest rate during the initial period of basal flow, 65.3±10.7pmol·min⁻¹. This increased further when the infusion rate rose to 10.5 ml·min⁻¹, but was significant only when the infusion rate was increased to 15.0 ml·min⁻¹. ATP was released at 41.5±11.5pmol·min⁻¹ during the initial period of basal flow. Its release significantly increased with flow and peaked at 15.0 ml·min ⁻¹. SP was released at a rate of 13.3±8.2pmol·min⁻¹ during the initial period of basal flow. Its rate of release was increased significantly the second time the flow was increased to 10.5 ml·min⁻¹ and increased even further when the flow was increased to 15.0 ml·min⁻¹. AVP was detected in one third of the samples collected during the initial period of basal flow, being released at a rate of 0.65±047pmol·min⁻¹. Only in the period following the 15.0 ml·min⁻¹ rate of flow was there a sustained increased release of AVP. These results are consistent with the view that ATP, SP, ET and AVP are released from vascular endothelial cells during changes in flow, and may contribute to the adjustments in local cerebrovascular tone.     

Measurement of CBF and CMRO2 using the continuous inhalation of CO2 and O2: Experimental validation using CO2 reactivity in the anaesthetised dog

Experimental support for the steady state ¹⁵O inhalation technique, as used to measure cerebral blood flow (CBF) and oxygen utilisation (CMRO₂), was obtained by describing the response of the cerebral vasculature to variations in arterial P_CO2 in 6 anaesthetised dogs. Measurements were made using a positron emission tomograph (ECAT II) and arterial blood sampling, during the sequential constant inhalation of C¹⁵O₂ and ¹⁵O₂. Values of CBF and CMRO₂ were calculated for a mixture of white and grey matter, using the steady state tracer equations derived by Jones et al. (1976). The mean CMRO₂ was 3.58 ± 0.81 ml O₂ · 100 ml⁻¹ · min⁻¹, whilst the mean CBF and OER (oxygen extraction ratio) values (for an arterial P_CO2 of 40 mm Hg) were 39.9 ml · 100 ml⁻¹ · min⁻¹ and 0.50 ± 0.06, respectively. Arterial P_CO2 was varied between 20 and 150 mm Hg. CBF was found to correlate closely with arterial P_CO2, resulting in a mean slope (specific reactivity) of 1.52 ± 0.38 ml · 100 ml⁻¹ · min⁻¹ · mm Hg⁻¹. Pooling the flow data resulted in a linear relationship between CBF (% change) and arterial P_CO2 in the range 20–70 mm Hg, with a slope (% reactivity) of 3.2% mm Hg⁻¹ (2 P < 0.001). The oxygen extraction ratio (OER) fell with increasing values of arterial P_CO2 resulting in a stable CMRO₂ throughout each study. There was no correlation between CMRO₂ and artificially increased CBF.

These results support and give confidence in the use of the ¹⁵O inhalation technique for measuring CBF, OER and CMRO₂.     

The resolution of dopamine and beta 1- and beta 2-adrenergic-sensitive adenylate cyclase activities in homogenates of cat cerebellum, hippocampus and cerebral cortex.

The stimulation of adenylate cyclase by dopamine and various β-adrenergic agonists has been investigated in homogenates from 3 areas of cat brain: the cerebral cortex, cerebellum and hippocampus. The purpose of the study was to determine whether the β-adrenergic receptors coupled to adenylate cyclase could be classified as either β₁ and β₂ subtypes in the different regions studied.

The stimulation of adenylate cyclase by the β-adrenergic agonist, (−)isoproterenol (5 × 10⁻⁶M), was completely blocked by the specific β-adrenergic antagonist, (−)alprenolol (10⁻⁵ M), but not by the dopaminergic antagonist, fluphenazine (10⁻⁵ M), whereas the stimulation of adenylate cyclase by (−)epinephrine (10⁻⁴ M) was blocked to varying extents by these two drugs in each of the 3 regions studied. The (−)epinephrine effect was always blocked in the combined presence of (−)alprenolol and fluphenazine. The adenylate cyclase stimulation by (−)epinephrine which is not blocked by (−)alprenolol was due to interaction of (−)epinephrine with a dopaminergic-sensitive adenylate cyclase which has been characterized in cerebral cortex, hippocampus and cerebellum.

Regional differences in the affinity of β-adrenergic-sensitive adenylate cyclase for various agonists were investigated in the presence of fluphenazine (10⁻⁵ M). In the cerebellum the potency order was (±)protokylol> (±)hydroxybenzylisoproterenol> (±)isoproterenol> (−)epinephrine> (±)salbutamol> (−)norepinephrine, indicating the presence of a β₂-adrenergic receptor. In the cerebral cortex the potency order was (−)isoproterenol> (±)protokylol> (±)hydroxybenzylisoproterenol> (−)epinephrine= (−)norepinephrine((±)salbutamol being inactive). A similar pattern was found in the hippocampus indicating the presence of a β₁-adrenergic receptor in these two regions. (±)Salbutamol was a partial agonist in the cerebellum and a competitive antagonist in the cerebral cortex.

The ratio of the antagonist potencies of (±)practolol and (±)butoxamine preferential β₁- and β₂-adrenergic antagonists respectively, to block the stimulation of adenylate cyclase was 25 in the cerebellum, compared to 0.5 in the cerebral cortex and 1.6 in the hippocampus. These results confirm the presence of a β₂ subtype of receptor coupled to adenylate cyclase in the former and β₁ subtypes in the latter two regions. The comparison between the affinities of a series of β-adrenergic agonists and antagonists for the β-adrenergic receptors coupled with an adenylate cyclase in cerebral cortex and cerebellum with their affinities for well characterized β₂-adrenergic receptors in lung and β₁-adrenergic receptor in heart substantiated this conclusion.     

Gene dose-dependent alterations in extraneuronal serotonin but not dopamine in mice with reduced serotonin transporter expression

Serotonin (5-HT) plays an integral regulatory role in mood, anxiety, cognition, appetite and aggressive behavior. Many therapeutic and illicit drugs that modulate these functions act at the serotonin transporter (SERT), thus a mouse model with reduced transporter expression was created to further investigate the effects of differential serotonin reuptake. In the present study, in vivo microdialysis was used to determine homeostatic alterations in extracellular 5-HT levels in unanesthetized SERT knockout mice. SERT^−/− mice had significantly higher levels of basal dialysate 5-HT than SERT^+/+ mice in striatum and frontal cortex. In addition, although gene-specific increases in 5-HT were evident, neuroadaptive alterations in dialysate dopamine levels were not detected in striatum. Zero net flux microdialysis was utilized to further investigate alterations in extracellular 5-HT. Using this method, a gene dose-dependent increase in extraneuronal 5-HT was observed in striatum (2.8 ± 1, 9.4 ± 1 and 18 ± 3 nM) and frontal cortex (1.4 ± 0.4, 3.5 ± 0.9 and 14 ± 1 nM) in SERT^+/+, SERT^+/− and SERT^−/− mice, respectively. Potassium stimulation revealed greater depolarization-induced increases in striatal 5-HT but not dopamine in SERT^−/− mice. Furthermore, dialysate 5-hydroxyindoleacetic acid (5-HIAA) levels were reduced in striatum in a gene dose-dependent manner, while DOPAC was unchanged in SERT knockout mice. Finally, determination of monoamine oxidase (MAO) activity revealed no significant differences in K_M or V_max of type-A or type-B isozymes indicating that alterations in SERT expression do not cause adaptive changes in the activities of these key catabolic enzymes. Overall, these results demonstrate that constitutive reductions in SERT are associated with increases in 5-HT in the extracellular signaling space in the absence of changes in dopamine neurochemistry. Furthermore, use of zero net flux microdialysis appears warranted in investigations of serotonergic synaptic function where modest changes in extracellular 5-HT are thought to occur in response to altered uptake.     

The effects of a physical exercise program,LEGOR and Minecraft activities on anxiety in underserved children with autism spectrum disorder

BackgroundAnxiety is a frequent comorbidity in children with autism spectrum disorder (ASD). Physical exercise is a low cost and easy-to-access intervention with therapeutic benefits for reducing anxiety in adults and adolescents. There are currently no randomized controlled trials on the feasibility and efficacy of a physical exercise intervention to reduce anxiety in younger children with ASD.Method148 children (6–12 years old) with ASD were randomized into a clinical trial to evaluate the efficacy of an 8-week exercise protocol designed to reduce anxiety specifically in younger children with ASD. Participants were randomized to an exercise intervention group (N = 76) or sedentary activity LEGO/Minecraft group (N = 72). Both programs were administered 1–3 times weekly for 8 weeks. Anxiety was assessed via parent ratings with the Child Behavior Checklist DSM-5 anxiety subscale (CBCL DSM-5) at weeks 1, 3, 6, and 8 as well as follow up at weeks 12 and 16. Secondary outcome measures included child self-reported anxiety (Screen for Child Anxiety Related Disorders; SCARED), sleep (Child’s Sleep Habits Questionnaire, CSHQ-ATN), physical activity level (Physical Activity Questionnaire, PAQ-C), and salivary cortisol measured at weeks 1, 3, 6, and 8.ResultsParent-rated (CBCL DSM-5) and self-reported (SCARED) anxiety scores showed improvements at weeks 3, 6 and 8 in both groups with no significant differences between the physical exercise and sedentary activity (LEGO/Minecraft) groups. In addition, the CBCL DSM-5 anxiety scores decreased only in the physical exercise group at weeks 12 and 16 compared to baseline with no significant difference from LEGO/Minecraft group. Sleep also showed improvements during weeks 6 and 8 in the physical exercise group but not in the LEGO/Minecraft group with no significant differences between the groups. Physical activity level was significantly increased in the physical exercise group compared to the LEGO/Minecraft group at week 8. Salivary cortisol did not show any significant changes from weeks 1–8 or differences between groups.ConclusionEight-week physical exercise and sedentary LEGO/Minecraft interventions reduced parent-rated and self-reported anxiety in 6–12-year-old underserved children with ASD with no significant difference between the intervention groups.     

The kinetic and structural characterization of the reaction of nafamostat with bovine pancreatic trypsin

Nafamostat mesilate (FUT-175), a synthetic serine protease inhibitor, is active against a number of the serine proteases involved in coagulation. This has been proposed as the basis of its anticoagulant activity. We investigated the reaction of Nafamostat with bovine pancreatic trypsin as a model system. It was shown to act as a time-dependent competitive inhibitor, and the inhibition constants for the binding of Nafamostat to trypsin (i.e., K_i) and the overall inhibition constants (i.e., K_i^*) were calculated to be 11.5 μM and 0.4±0.14 nM, respectively. The second-order rate constant for the reaction was 4.5±0.19×10⁵ M⁻¹s⁻¹, and the product released following the acylation step, 6-amidino-2-naphthol, showed mixed-type inhibition. The competitive (K_ic) and uncompetitive (K_iu) inhibition constants were 14.7 μM and 19.5 μM, respectively. Formation of the acyl-enzyme intermediate was dissected into at least two steps, with rates of 0.9 s⁻¹ and 195 s⁻¹. The deacylation step was relatively much slower (3.2±0.19×10⁻⁵ s⁻¹), enabling the mass spectroscopic analysis of the acyl-enzyme intermediate, which confirmed the covalent attachment of 4-guanidinobenzoic acid to trypsin. The product of the deacylation step, 4-guanidinobenzoic acid, showed no inhibition up to a concentration of 200 μM. These data strongly suggest that while Nafamostat is a potent inhibitor of trypsin, it is actually an extremely poor substrate, and that apparent inhibition is due to the competitive formation of a very stable acyl-enzyme intermediate, analogous to some other active site titrants.     

Vasodilatory effects of okadaic acid on the canine cerebral artery

We investigated the in vivo and in vitro Vasodilatory effects of okadaic acid, an inhibitor of protein phosphatases, in canine basilar arteries. Angiography revealed that the intracisternal injection of okadaic acid produced a long-lasting increase in the internal diameter of the canine basilar artery. The maximal increases in diameter induced by 1 and 10 nmol of okadaic acid were 23.3 ± 13.5 and 33.8 ± 11.9%, respectively. Okadaic acid in the concentrations of 10⁻⁷ and 10⁻⁶M also exerted a dose-dependent, long-lasting relaxation without any contraction in isolated basilar arteries, even in the resting condition. Similar effects (ED₅₀ values and maximal relaxation) were observed in arterial strips precontracted with K⁺, prostaglandin F2, and phorbol 12-myristate 13-acetate. These in vito and in vivo results suggest that inhibition of protein phosphatases by okadaic acid produces a vasodilation in the cerebral artery.     

Neuroendocrine and blood pressure responses to rectal distensions in individuals with high and low visceral pain sensitivity

BACKGROUND: The mechanisms of interindividual variations in visceral pain sensitivity remain poorly understood. We characterized the neuroendocrine responses to rectal distensions in healthy individuals with high vs. low rectal pain sensitivity. METHODS: Rectal sensory and pain thresholds were determined, and a series of random painful distensions was carried out. Eighteen subjects were stratified into groups with a low rectal pain threshold ("High Sensitivity" group) vs. a high rectal pain threshold ("Low Sensitivity" group) by median split, and were compared with regard to adrenocorticotropic hormone (ACTH) and cortisol, cardiovascular, and emotional responses. RESULTS: Distensions led to an anticipatory stress response, reflected by elevated baseline anxiety, and increased baseline ACTH and cortisol in both groups. In response to distensions, the "Low Sensitivity" group showed significantly greater ACTH and cortisol concentrations analysis of variance (ANOVA time x group for ACTH: p<.05; for cortisol: p<.01), and elevated diastolic blood pressures (BP) (ANOVA group: p<.01) when compared to the "High Sensitivity" group. CONCLUSIONS: Painful rectal distensions are associated with a pronounced anticipatory stress response, reflected by elevated anxiety and elevated stress hormones. Individuals with high rectal pain sensitivity differ from those with low pain sensitivity in distension-induced hormonal and blood pressure responses, suggesting that neuroendocrine responses may be relevant to the pathophysiology of visceral hyperalgesia.     

Effect of aspirin on constitutive nitric oxide synthase and the biovailability of NO

Introduction: Aspirin decreases the activity of iNOS and the formation of prostanoids. Constitutive nitric oxide synthase (cNOS) is present in endothelial cells, platelets, leukocytes and neurons, yet no data are available on the effect of aspirin on cNOS and the bioavailability of NO produced by this enzyme. Materials and methods: Human umbilical vein endothelial cells (HUVECs), rat adrenal gland pheocromocytoma cells (PC-12) and human platelets were incubated with different aspirin concentrations. The kinetics of NO, O₂⁻ and ONOO⁻ release were measured simultaneously in single cells or platelet suspensions using tandem electrochemical nanosensors. The NO, O₂⁻ and ONOO⁻ release from cells and platelets was stimulated with calcium ionophore and collagen, respectively. cNOS expression was estimated by Western blot analysis. Results: Incubation of HUVECs and PC-12 with 10⁻⁵ mol/l of aspirin increased cNOS expression by 70±7% and 50±5, respectively. However, the NO concentration increased only by 33% in HUVECs incubated with the same aspirin concentration. Incubation of HUVECs with aspirin also increased the O₂⁻ and ONOO⁻ production. Therefore the bioavailability of NO increased only slightly in endothelium and did not reflect the increase in eNOS. This was in contrast to platelets, where maximal NO bioavailability almost doubled after incubation with aspirin. Conclusions: Aspirin did not have a significant effect on the NO bioavailability in endothelial cells. However, aspirin highly improved the NO production in platelets. The high NO production in platelets may counteract the effect of thromboxane, inhibit platelet aggregation, and compensate for the reduction of prostacycline concentration by aspirin.     

Characterization of electrogenic Na/K pump in rat neostriatal neurons

The electrogenic Na/K pump current (Ip) was studied in the dissociated neostriatal neurons of the rat by using the nystatin-perforated patch recording mode. The Ip was activated by external K⁺ in a concentration-dependent manner with an EC₅₀ of 0.7 mM at a holding potential (V_H) of −40 mV. Other monovalent cations also caused Ip and the order of potency was Tl⁺>K⁺, Rb⁺>NH₄⁺, Cs⁺>>>Li⁺. The Ip decreased with membrane hyperpolarization in an external solution containing 150 mM Na⁺, while the Ip did not show such voltage dependency without external Na⁺. Ouabain showed a steady-state inhibition of Ip in a concentration- and temperature-dependent manner at a V_H of −40 mV. The IC₅₀ values at 20 and 30°C were 7.1×10⁻⁶ and 1.3×10⁻⁶ M, respectively. The decay of Ip after adding ouabain well fitted with a single exponential function. At a V_H of −40 Mv, the association (k₊₁) and dissociation (k₋₁) rate constants estimated from the time constant of the current decay at 20°C were 4.0×10² s⁻¹ M⁻¹ and 6.3×10⁻³ s⁻¹, respectively. At 30°C, k₊₁ increased to 2.8×10³ s⁻¹ M⁻¹ while k₋₁ showed no such change with a value of 1.8×10⁻³ s⁻¹. A continuous Na⁺ influx was demonstrated by both the Na⁺-dependent leakage current and tetrodotoxin-sensitive Na⁺ current, which resulted in the continuous activation of the Na/K pump. It was thus concluded that the Na/K pump activity was well-maintained in the dissociated rat neostriatal neurons with distinct functional properties and that the activity of the pump was tightly connected with Na⁺ influxes.     

Dynamic cerebral autoregulation is impaired in glaucoma

Objectives: Autonomic and endothelial dysfunction is likely to contribute to the pathophysiology of normal pressure glaucoma (NPG) and primary open angle glaucoma (POAG). Although there is evidence of vasomotor dysregulation with decreased peripheral and ocular blood flow, cerebral autoregulation (CA) has not yet been evaluated. The aim of our study was to assess dynamic CA in patients with NPG and POAG. Materials and Methods: In 10 NPG patients, 11 POAG patients and 11 controls, we assessed the response of cerebral blood flow velocity (CBFV) to oscillations in mean arterial pressure (MAP) induced by deep breathing at 0.1 Hz. CA was assessed from the autoregressive cross-spectral gain between 0.1 Hz oscillations in MAP and CBFV. Results: 0.1 Hz spectral powers of MAP did not differ between NPG, POAG and controls; 0.1 Hz CBFV power was higher in patients with NPG (5.68±1.2 cm² s⁻²) and POAG (6.79±2.1 cm² s⁻²) than in controls (2.40±0.4 cm² s⁻²). Furthermore, the MAP–CBFV gain was higher in NPG (2.44±0.5 arbitrary units [a.u.]) and POAG (1.99±0.2 a.u.) than in controls (1.21±0.1 a.u.). Conclusion: Enhanced transmission of oscillations in MAP onto CBFV in NPG and POAG indicates impaired cerebral autoregulation and might contribute to an increased risk of cerebrovascular disorders in these diseases.     

The effect of hydrocortisone and adrenocorticotrophic hormone on monoamine oxidase and tyrosine hydroxylase in explant cultures of embryonic chick sympathetic ganglia

Sympathetic ganglia from 13- to 15-day-old embryonic chicks were cultured for up to 2 days in Leighton tubes. The influence of hydrocortisone and ACTH added to the culture medium on the enzymes monoamine oxidase (MAO) and tyrosine hydroxylase was studied. Hydrocortisone(5 × 10⁻⁵ M) had no effect on tyrosine hydroxylase but increased MAO activity by up to 46% over control values under conditions of low or zero nerve growth factor (NGF) concentration. ACTH also increased ganglionic MAO activity, the effect again depending on NGF concentration. This time the maximal response (an increase of 50% over controls) was seen at high NGF concentrations. This response was similar to the effect of 1mM dibutyryl cyclic AMP, and was blocked by1 × 10⁻⁵ M propranolol and10 μM prostaglandin E₁. ACTH only slightly increased tyrosine hydroxylase activity and this effect was due to a small (18%) increase in sympathetic neurone number. Guanosine 5′-diphosphate(0.5mM) was found to increase tyrosine hydroxylase activity by 57% and this effect was blocked by the presence of ACTH.     

Role of AT1 receptors in area postrema on baroreceptor reflex in spontaneously hypertensive rats

Intravenous injection of angiotensin II type 1 (AT₁) receptor antagonist improves the baroreceptor reflex gain in spontaneously hypertensive rats (SHRs). To investigate the role of area postrema in the modulation of the baroreflex control by AT₁ receptor, the effects of intravenous injection of CV-11974 (AT₁ receptor antagonist) on the baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) were examined in sham and area postrema-lesioned SHRs. The baseline mean arterial pressure was similar in both groups. However, baseline heart rate was significantly lower (p<0.01) in area postrema-lesioned SHR than in sham-lesioned SHR, 307±11 and 365±10 beats/min (bpm), respectively. Intravenous CV-11974 (0.05 mg/kg) significantly decreased mean arterial pressure; however, it did not change HR and RSNA in either group. Reflex changes in RSNA and HR were elicited by intravenous infusion of either phenylephrine or sodium nitroprusside before and after intravenous injection of CV-11974. Intravenous CV-11974 increased baroreflex control of RSNA (G_max; −1.57±0.08 vs. −1.92±0.12%/mmHg, p<0.05) and HR (G_max; −0.54±0.12 vs. 1.25±0.24 bpm/mmHg, p<0.05) in sham-lesioned SHRs. However, intravenous CV-11974 failed to alter the baroreflex sensitivities in area postrema-lesioned SHRs. These results suggest that the area postrema does not play a crucial role in maintenance of high blood pressure in adult SHRs, and that the improvement of baroreflex control of RSNA and HR by intravenous CV-11974 is mediated via the area postrema in SHRs.