Adrenergic Mechanisms Research Articles

Huperzia saururus Lam. Trevis. (Lycopodiaceae) facilitates ejaculation in spinal cord transected male rats

Ethnopharmacological relevanceHuperzia saururus (Lam.) Trevis. has an extensive ethnopharmacological use, mainly because of its aphrodisiac properties. The species is consumed as decoctions or infusions in traditional medicine. The purpose of the present research was to determine if Huperzia saururus is able to increase sexual potency by evaluating the ejaculatory response, in the presence of a decoction in spinal cord transected male rats. Materials and methodsThe fictive ejaculation model to record the rhythmic contractions of the bulbospongiosus muscles that accompany ejaculation as an indicator of ejaculation occurrence was used. Sexually experienced male Wistar rats were used. The activation of the fictive ejaculation by the i.v. administration of a decoction was tested, as well as the effects of the oxytocinergic, cholinergic, adrenergic and nitrergic antagonism upon the pro-ejaculatory activity of Huperzia saururus. ResultsDecoction (3µg/animal) was able to activate the fictive ejaculation in spinal male rats, producing a statistically significant diminution on the latency of discharge parameter and a statistically significant augment for the number of discharges. Moreover, when sequential treatments using antagonists plus decoction were administered, the effects produced showed that prazosin prevent the pro-ejaculatory effect of the decoction and that the four antagonists assayed blocked the facilitatory effect of Huperzia saururus since the facilitation in the latency of response was prevented, and the number of discharges was reduced. Together these findings support the notion that the decoction exerts an aphrodisiac effect influencing the ejaculatory potency which is partially mediated by oxytocinergic, cholinergic, adrenergic and nitrergic spinal mechanisms. ConclusionIn agreement to the ethnopharmacological uses, Huperzia saururus decoction has aphrodisiac properties by influence on the ejaculatory potency.

A spinal GABAergic mechanism is necessary for bladder inhibition by pudendal afferent stimulation.

Electrical stimulation of pudendal afferents can inhibit bladder contractions and increase bladder capacity. Recent results suggest that stimulation-evoked bladder inhibition is mediated by a mechanism other than activation of sympathetic bladder efferents in the hypogastric nerve, generating α-adrenergic receptor-mediated inhibition at the vesical ganglia and/or β-adrenergic receptor-mediated direct inhibition of the detrusor muscle. We investigated several inhibitory neurotransmitters that may instead be necessary for stimulation-evoked inhibition and found that intravenous picrotoxin, a noncompetitive GABAA antagonist, significantly and reversibly blocked pudendal afferent stimulation-evoked inhibition of bladder contractions in a dose-dependent manner. Similarly, intravenous picrotoxin also blocked pudendal afferent stimulation-evoked inhibition of nociceptive bladder contractions evoked by acetic acid infusion. Furthermore, intrathecal administration of picrotoxin at the lumbosacral spinal cord also blocked bladder inhibition by pudendal afferent stimulation. On the other hand, glycinergic, adrenergic, or opioidergic mechanisms were not necessary for bladder inhibition evoked by pudendal afferent stimulation. These results identify a lumbosacral spinal GABAergic mechanism of bladder inhibition evoked by pudendal afferent stimulation.

Lipocalin 2 Regulates Brown Fat Activation via a Nonadrenergic Activation Mechanism

In this study, we report that lipocalin 2 (Lcn2), a recently characterized adipokine/cytokine, is a novel regulator of brown adipose tissue (BAT) activation by modulating the adrenergic independent p38 MAPK-PGC-1α-UCP1 pathway. Global Lcn2 knock-out (Lcn2(-/-)) mice have defective BAT thermogenic activation caused by cold stimulation and decreased BAT activity under high fat diet-induced obesity. Nevertheless, Lcn2(-/-) mice maintain normal sympathetic nervous system activation as evidenced by normal catecholamine release and lipolytic activity in response to cold stimulation. Further studies showed that Lcn2 deficiency impairs peroxisomal and mitochondrial oxidation of lipids and attenuates cold-induced Pgc1a and Ucp1 expression and p38 MAPK phosphorylation in BAT. Moreover, in vitro studies showed that Lcn2 deficiency reduces the thermogenic activity of brown adipocytes. Lcn2(-/-) differentiated brown adipocytes have significantly decreased expression levels of brown fat markers, decreased p38 MAPK phosphorylation, and decreased mitochondrial oxidation capacity. However, Lcn2(-/-) brown adipocytes have normal norepinephrine-stimulated p38 MAPK and hormone-sensitive lipase phosphorylation and Pgc1a and Ucp1 expression, suggesting an intact β-adrenergic signaling activation. More intriguingly, recombinant Lcn2 was able to significantly stimulate p38 MAPK phosphorylation in brown adipocytes. Activating peroxisome proliferator-activated receptor γ, a downstream effector of PGC-1α, by thiazolidinedione administration fully reverses the BAT function of Lcn2(-/-) mice. Our findings provide evidence for the novel role Lcn2 plays in oxidative metabolism and BAT activation via an adrenergic independent mechanism.

Combining Opioid and Adrenergic Mechanisms for Chronic Pain

Chronic pain is a highly prevalent medical problem in the United States. Although opioids and serotonin-norepinephrine reuptake inhibitors (SNRIs) have demonstrated efficacy for relief of chronic pain, each has risks of adverse events in patients. Because of the risk of opioid abuse and addiction, combinations reducing opioid requirements are particularly valuable. Opioid and SNRI agents relieve pain by different pathways; concurrent use of each agent separately offers many potential benefits: complementary and possibly synergistic analgesic efficacy, separate titrations of opioid and SNRI effects, and the reduction of opioid requirements. However, few clinical studies have investigated the ideal ratios for combinations of opioids and SNRIs. A number of factors affect whether specific combinations have additive, synergistic, less than additive efficacy, or increase adverse events in patients, including general pharmacokinetic considerations, the potential for pharmacodynamic drug interactions, dose, and timing. Because there is little clinical evidence guiding combination therapy with separate opioid and SNRI agents, using single-molecule agents provides safe and effective therapy and should be the first option presented to patients. The use of empiric combinations of separate opioid and SNRI combinations needs to be considered in light of clinical cautions, including the lack of published evidence to guide dose conversion from any opioid to tramadol or to tapentadol, and vice versa; the need to avoid combinations with known drug interactions; and the need to titrate the dose when adding an SNRI to an opioid, and vice versa.

Akt signaling mediates the anabolic action of sympathetic innervation in brown adipose tissue from cold‐exposed rats (1161.6)

Previous studies from our lab have demonstrated that sympathetic nervous system (SNS) exerts an anabolic effect on muscle protein metabolism. However, the physiological role of SNS in the maintenance of brown adipose tissue (BAT) mass, the main site of organism heat production, is unclear. Thus, our goal was to investigate the adrenergic mechanisms controlling BAT protein metabolism. For this, adult Wistar rats were submitted to surgical sympathetic hemidenervation (DEN) of BAT. Six days later, rats were exposed to cold (4oC) for 2 days. The phosphorylation levels of proteins involved in the control of proteolytic pathways and protein synthesis were analyzed by Western blotting. BAT noradrenaline was measured by HPLC. Cold‐exposed animals exhibited an increase in BAT noradrenaline content and in the levels of total (2‐fold) and mitochondrial (60%) proteins. These effects were associated with an up‐regulation in the phosphorylation levels of AktSer (70%), GSK3α (30%) and 4E‐BP1 (2‐fold), which are key mediators involved in protein synthesis. Furthermore, BAT from cold‐exposed animals also showed an increase in the phosphorylation levels of the transcription factor Foxo1, which could inhibit the expression of proteolytic genes. All these effects were abolished in cold‐exposed rats submitted to DEN. In summary, the data suggest that SNS plays an important role in cold‐induced increase in total and mitochondrial proteins in BAT and these effects may be partially mediated by downstream targets of AKT such as FoxO1, GSK3a and 4E‐BP1.Grant Funding Source: Supported by CNPq and FAPESP (13/17111‐0; 12/24524‐6).

Role of α- and β-adrenergic Mechanisms in the Pathogenesis of Pulmonary Injuries Characterized by Edema, Inflammation and Fibrosis

Adrenergic mechanisms are involved in the formation of several types of pulmonary edema (PE) such as neurogenic pulmonary edema (NPE) or PE in patients with pheochromocytoma, but also in the development of pulmonary fibrosis and pulmonary hypertension. In severe cases of PE such as in the adult respiratory distress syndrome (ARDS), PE is typically accompanied by inflammation and followed by pulmonary vascular hypertrophy and pulmonary fibrosis. Norepinephrine and other adrenoceptor agonists are known to provoke activation of proinflammatory cytokines such as interleukin (IL)-1 and IL-6. These cytokines are involved both in the pathogenesis of PE and of pulmonary fibrosis. We therefore assume that adrenergic mechanisms may have an important role in the pathogenesis of pulmonary injuries characterized by edema, inflammation and fibrosis. The contribution of adrenoceptor stimulation, particularly the distinct role of α- and β-adrenergic mechanisms, to the development of PE and pulmonary fibrosis is reviewed in this paper.

Coronary artery disease and age: beyond atherosclerosis

Coronary artery disease and age: beyond atherosclerosis

Guanfacine ameliorates hypobaric hypoxia induced spatial working memory deficits

Hypobaric hypoxia (HH) observed at high altitude causes mild cognitive impairment specifically affecting attention and working memory. Adrenergic dysregulation and neuronal damage in prefrontal cortex (PFC) has been implicated in hypoxia induced memory deficits. Optimal stimulation of alpha 2A adrenergic receptor in PFC facilitates the spatial working memory (SWM) under the conditions of adrenergic dysregulation. Therefore the present study was designed to test the efficacy of alpha 2A adrenergic agonist, Guanfacine (GFC), to restore HH induced SWM deficits and PFC neuronal damage. The rats were exposed to chronic HH equivalent to 25,000ft for 7days in an animal decompression chamber and received daily treatment of GFC at a dose of 1mg/kg body weight via the intramuscular route during the period of exposure. The cognitive performance was assessed by Delayed Alternation Task (DAT) using T-Maze and PFC neuronal damage was studied by apoptotic and neurodegenerative markers. Percentage of correct choice decreased significantly while perseverative errors showed a significant increase after 7days HH exposure, GFC significantly ameliorated the SWM deficits and perseveration. There was a marked and significant increase in chromatin condensation, DNA fragmentation, neuronal pyknosis and fluoro Jade positive cells in layer II of the medial PFC in hypoxia exposed group, administration of GFC significantly reduced the magnitude of these changes. Modulation of adrenergic mechanisms by GFC may serve as an effective countermeasure in amelioration of prefrontal deficits and neurodegenerative changes during HH.

Effects of ginsenosides on rat jejunal contractility

Context: Ginsenosides are primary active ingredients of ginseng, which are believed to have various health benefits. It is found that the biotransformation of ginsenosides mainly takes place in the gastrointestinal tract and the information about ginsenosides-exerted effects on intestinal contractility is not sufficient.Aims: The present study proposed that ginsenosides could exert stimulatory or inhibitory effects on intestinal motility depending on the assay condition-related intestinal contractile states and was to characterize the effects of ginsenosides on intestinal motility.Methods: Jejunal contractility determination, Western blotting analysis, and real-time polymerase chain reaction were performed to test the effects of total ginsenosides isolated from Panax ginseng C. A. Mey (Araliaceae) root.Results: The results showed that ginsenosides at the fixed concentration of 20 mg/L exerted bidirectional regulation (BR) on the contractility of isolated jejunal segment (IJS), depending on the contractile states. The contractility of IJS was increased by ginsenosides in low contractile states, which were correlated to the cholinergic activation, and the contractility of IJS was decreased by ginsenosides in high contractile states, which were correlated to the adrenergic activation and nitric oxide related mechanisms. Ginsenosides-induced BR was abolished in the absence of Ca2+ or by using tetrodotoxin, implicating the requirement of Ca2+ and the enteric nervous system. Effects of ginsenosides on myosin light chain phosphorylation and the mRNA expression of myosin light chain kinase were also bidirectional.Discussion and conclusion: Results suggest that ginsenosides may have the potential clinical implication for reliving the symptoms of alternative hypo- and hyper-intestinal motility.

86. Neuroendocrine mediators regulate production of B cell activating factor of the tumor necrosis factor family (BAFF) in human synovial fibroblasts

BAFF is a cytokine important for the stimulation and survival of autoreactive B cells and therefore might play a role in several autoimmune diseases. In psoriasis arthritis (PsA), we found that BAFF correlates with disease activity and testosterone, but only in male patients, suggesting a role for sex hormones in the regulation of BAFF. Therefore, we wanted to determine if BAFF in rheumatoid arthritis (RA) and osteoarthritis (OA) synovial fibroblasts (SF) is regulated by neuroendocrine mediators. SF isolated from RA ( n = 10) and OA ( n = 10) patients were cultured in the presence or absence of Interferon- γ (IFN γ ), IL-1, lipopolysaccharide (LPS), tumor necrosis factor (TNF) or cortisol at different concentrations for 48 and 72 h. IFN- γ was used in subsequant experiments, because it was the best inductor of BAFF in RA and OA SFs. IFN- γ -induced BAFF production was decreased by dihydrotestosterone in a concentration-dependent manner at 24 h, however the effect was reversed after 72 h of culture. The effect was specifically inhibited by nilutamid, a testosterone receptor antagonist. Furthermore, α -adrenergic mechanisms decreased and β -adrenergic mechanisms increased BAFF in OA and RA SFs. In general the effects were more pronounced in RA as compared to OA SFs. Taken together, BAFF production in synovial fibroblasts is modulated by testosterone and adrenergic stimuli. Therefore, the influence of neuroendocrine mediators in the context of arthritis might be in part mediated by regulating BAFF.

Toward Rational Pharmacotherapy for Posttraumatic Stress Disorder: Reprise

Toward Rational Pharmacotherapy for Posttraumatic Stress Disorder: Reprise

Esmolol activates endogenous neurokinin activity inhibiting infarction-induced arrhythmias in rats: Novel mechanisms of anti-arrhythmia

Endogenous neurokinin and adrenergic mechanisms might co-participate in the pathology of acute myocardial infarction (MI). This study sought to investigate the role of endogenous neurokinin and its relationship with β1-adrenergic mechanism in the infarction induced arrhythmias.In 60min of MI in rats, the contents of substance P (SP), a native agonist of neurokinin 1 receptor (NK1-R), norepinephrine (NE), NK1-R and β1-adrenergic receptor in the myocardium at risk of ischemia were examined and the ventricular arrhythmias were analyzed. The effects of pretreatment with D-SP (152ng/kg), a specific antagonist of NK1-R, esmolol (10mg/kg), a specific blocker of β1-adrenergic receptor, and a combination of the two blockers were studied. The results showed that the overlaps of up-regulation of NE, SP and the increase of ventricular arrhythmias were observed. D-SP exacerbated the episodes and duration of VT & VF by 54% and 104%, respectively (all P<0.05). Esmolol inhibited the morbidity rate, the episodes and the duration of VT & VF by 66%, 92% and 95%, respectively. Surprisingly, esmolol significantly attenuated the arrhythmogenic effect of D-SP throughout the MI, beyond the time span of esmolol action, during which a significant up-regulation of the NK1-R (by 19%, P<0.05) was detected.In conclusion, the findings of this study may indicate an anti-arrhythmic effect of endogenous neurokinin mechanism, through the activation of which, via up-regulation of NK1 receptor, esmolol may exert its anti-arrhythmic action at the early time of acute myocardial infarction.

Oral sapropterin augments reflex vasoconstriction in aged human skin through noradrenergic mechanisms

Reflex vasoconstriction is attenuated in aged skin due to a functional loss of adrenergic vasoconstriction. Bioavailability of tetrahydrobiopterin (BH4), an essential cofactor for catecholamine synthesis, is reduced with aging. Locally administered BH4 increases vasoconstriction through adrenergic mechanisms in aged human skin. We hypothesized that oral sapropterin (Kuvan, a pharmaceutical BH4) would augment vasoconstriction elicited by whole-body cooling and tyramine perfusion in aged skin. Ten healthy subjects (age 75 ± 2 yr) ingested sapropterin (10 mg/kg) or placebo in a randomized, double-blind crossover design. Venous blood samples were collected prior to, and 3 h following ingestion. Three intradermal microdialysis fibers were placed in the forearm skin for local delivery of 1) lactated Ringer, 2) 5 mM BH4, and 3) 5 mM yohimbine + 1 mM propranolol (Y+P; to inhibit adrenergic vasoconstriction). Red cell flux was measured at each site by laser-Doppler flowmetry (LDF) as reflex vasoconstriction was induced by lowering and then clamping whole-body skin temperature (Tsk) using a water-perfused suit. Following whole-body cooling, subjects were rewarmed and 1 mM tyramine was perfused at each site to elicit endogenous norepinephrine release from the perivascular nerve terminal. Cutaneous vascular conductance was calculated as CVC = LDF/mean arterial pressure and expressed as change from baseline (ΔCVC). Plasma BH4 was elevated 3 h after ingestion of sapropterin (43.8 ± 3 vs. 19.1 ± 2 pmol/ml; P < 0.001). Sapropterin increased reflex vasoconstriction at the Ringer site at Tsk ≤ 32.5°C (P < 0.05). Local BH4 perfusion augmented reflex vasoconstriction at Tsk ≤ 31.5°C with placebo treatment only (P < 0.05). There was no treatment effect on reflex vasoconstriction at the BH4-perfused or Y+P-perfused sites. Sapropterin increased pharmacologically induced vasoconstriction at the Ringer site (-0.19 ± 0.03 vs. -0.08 ± 0.02 ΔCVC; P = 0.01). There was no difference in pharmacologically induced vasoconstriction between treatments at the BH4-perfused site (-0.16 ± 0.04 vs. -0.14 ± 0.03 ΔCVC; P = 0.60) or the Y+P-perfused site (-0.05 ± 0.02 vs.-0.06 ± 0.02 ΔCVC; P = 0.79). Sapropterin increases both reflex (cold-induced) and pharmacologically induced vasoconstriction through adrenergic mechanisms and may be a viable intervention to improve reflex vasoconstriction in aged humans.

‘Cold as ice’, why do old coronary arteries pay the price?

‘Cold as ice’, why do old coronary arteries pay the price?

Contribution of sympathetic activation to coronary vasodilatation during the cold pressor test in healthy men: effect of ageing

The sympathetic nervous system is an important regulator of coronary blood flow. The cold pressor test (CPT) is a powerful sympathoexcitatory stressor. We tested the hypotheses that: (1) CPT-induced sympathetic activation elicits coronary vasodilatation in young adults that is impaired with advancing age and (2) combined α- and β-adrenergic blockade diminishes/abolishes these age-related differences. Vascular responses of the left anterior descending artery to the CPT were determined by transthoracic Doppler echocardiography before (pre-blockade) and during (post-blockade) systemic co-administration of α- and β-adrenergic antagonists in young (n = 9; 26 ± 1 years old, mean ± SEM) and older healthy men (n = 9; 66 ± 2 years old). Coronary vascular resistance (CVR; mean arterial pressure/coronary blood velocity) was used as an index of vascular tone. CPT decreased CVR (i.e. coronary vasodilatation occurred) in young ( -33 ± 6%), but not older men ( -3 ± 4%; P < 0.05 vs. young) pre-blockade. Adrenergic blockade abolished CPT-induced coronary vasodilatation in young men ( -33 ± 6% vs. 0 ± 6%, pre-blockade vs. post-blockade, respectively; P < 0.05) such that responses post-blockade mirrored those of older men ( -3 ± 4% vs. 8 ± 9%; both P > 0.05 compared to young pre-blockade). Impaired CPT-induced coronary vasodilatation could not be explained by a reduced stimulus for vasodilatation as group and condition effects persisted when CVR responses were expressed relative to myocardial oxygen demand (rate-pressure product). These data indicate that the normal coronary vascular response to sympathetic activation in young men is pronounced vasodilatation and this effect is lost with age as the result of an adrenergic mechanism. These findings may help explain how acute sympathoexcitation may precipitate angina and coronary ischaemic events, particularly in older adults.

Estradiol effects on subcutaneous adipose tissue lipolysis in premenopausal women are adipose tissue depot specific and treatment dependent

Estrogen has direct effects within adipose tissue and has been implicated in regional adiposity; however, the influence of estrogen on in vivo lipolysis is unclear. The purpose of this study was to investigate the effect of local 17β-estradiol (E(2)) on subcutaneous adipose tissue (SAT) lipolysis in premenopausal women. In vivo lipolysis (dialysate glycerol) was measured in 17 women (age 27.4 ± 2.0 yr, BMI 29.7 ± 0.5 kg/m(2)) via microdialysis of abdominal (AB) and gluteal (GL) SAT. Glycerol was measured at baseline and during acute interventions to increase lipolysis including local perfusion of isoproterenol (ISO, β-adrenergic agonist, 1.0 μmol/l), phentolamine (PHEN, α-adrenergic antagonist, 0.1 mmol/l), and submaximal exercise (60% Vo(2peak), 30 min); all with and without coperfusion of E(2) (500 nmol/l). E(2) coperfusion blunted the lipolytic response to ISO in AB (E(2) 196 ± 31%, control 258 ± 26%, P = 0.003) but not in GL (E(2) 113 ± 14%, control 111 ± 12%, P = 0.43) adipose tissue. At rest, perfusion of PHEN with ISO did not change dialysate glycerol. Submaximal exercise during ISO + PHEN increased dialysate glycerol in the AB (56 ± 9%) and GL (62 ± 12%) regions. Probes perfused with E(2) during exercise and ISO + PHEN had an increased lipolytic response in AB (90 ± 9%, P = 0.007) but a lower response in GL (35 ± 7%, P = 0.05) SAT compared with no-E(2) conditions. E(2) effects on lipolysis are region specific and may work through both adrenergic and adrenergic-independent mechanisms to potentiate and/or blunt SAT lipolysis in premenopausal women.

Preclinical Profile of Bacopasides From Bacopa monnieri (BM) As An Emerging Class of Therapeutics for Management of Chronic Pains

Chronic pains management costs billions of dollars in medical exchequer to the world population. Additionally, 77% of people with chronic pains also have a degree of medically treatable depression. Opioids have a narrower safety index due to their side effects associated with its tolerance, hyperalgesia and subsequent dependence. Likewise, non steroidal anti-inflammatory drugs and anticonvulsants, also have limited safety and tolerability profile in the management of chronic pains. Bacopa monnieri, a renowned ayurvedic medicine has a strong antidepressant effect and significant antinociceptive effect, which is comparable to the effect of morphine via adenosinergic, opioidergic, and adrenergic mechanisms. BM has been also reported to be effective in neuropathic pains. Additionally, it has a strong anti-inflammatory effect mediated via COX-2 inhibitory mechanism. Apart from its effect of augmenting morphine analgesia, BM also inhibits opioid-withdrawal induced hyperalgesia, and acquisition and expression of morphine tolerance. BM is reported to have a strong protective effect against toxic effects of opiates on major organs like brain, kidneys and heart. BM is well documented to be safe and well tolerated herbal therapy in multiple clinical trials including various age groups. This minireview evaluated the preclinical data that highlights potential of BM as a future candidate for clinical management of chronic pains.

Adrenergic Genetic Mechanisms in Hypertension and Hypertensive Kidney Disease

Catecholamine secretory traits were significantly heritable, as were stress-induced blood pressure changes. Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis. In the tyrosine hyroxylase promoter, significant associations were found for urinary catecholamine excretion and for blood pressure response to stress. TH promoter haplotype 2 (TGGG) showed pleiotropy, increasing both norepinephrine excretion and blood pressure during stress. In hypertension, 2 independent case-control studies (1,266 subjects with 53% women and 927 subjects with 24% women) replicated the effect of C-824T in the determination of blood pressure. Chromogranin A (CHGA) plays a fundamental role in the biogenesis of catecholamine secretory granules. Changes in the storage and release of CHGA in clinical and experimental hypertension prompted us to study whether genetic variation at the CHGA locus might contribute to alterations in autonomic function, and hence hypertension and its target organ consequences such as hypertensive kidney disease (nephrosclerosis). Systematic polymorphism discovery across the human CHGA locus revealed such regulatory regions as the proximal promoter and 3'-UTR. In chromaffin cell-transfected CHGA 3'-UTR and promoter/luciferase reporter plasmids, the functional consequences of the regulatory/non-coding allelic variants were documented. Variants in both the proximal promoter and the 3'-UTR displayed statistical associations with hypertension and hypertensive end stage renal disease. Therefore, I would like to review the common genetic variation in TH and CHGA as a cause of inter-individual variation in sympathetic activity, and ultimately blood pressure and hypertensive kidney disease.

Evaluation of enalapril affecting the renin-angiotensin system in normal and stress-induced rats based on urinary metabolites of amines and cortisol

The renin-angiotensin system is distributed centrally as well as peripherally, which works in association with SNS and HPA in stress. Angiotensin is considered one of the principal hormones for bringing out stress-related changes. To find the influence of enalapril on the neuromediator of CNS and periphery, the present work was carried out. The assessment of the transmitter levels was done by estimating major urinary stress metabolites like vanillylmandelic acid, 5-hydroxyindoleacetic acid, 6-β-hydroxycortisol and homovanillic acid in normal and stress-induced conditions and also in the absence and presence of enalapril treatment in rats. Groups of rats were subjected to a forced swim stress one hour after daily treatment of enalapril. The 24 h urinary excretion of vanillylmandelic acid, 5-hydroxyindoleacetic acid, 6-β-hydroxycortisol and homovanillic acid was determined in all groups under normal and stressed-induced conditions. Daily administration of enalapril at doses of 3, 10 and 30 mg/kg/body weight inhibited the stress-induced urinary biochemical changes. However, treatment with enalapril in normal conditions increased the excretion of all selected metabolites. It can be speculated that enalapril prevented stress-induced increases of adrenergic, serotonergic and cortical mechanisms.

Elevated local skin temperature impairs cutaneous vasoconstrictor responses to a simulated haemorrhagic challenge while heat stressed

During a simulated haemorrhagic challenge, syncopal symptoms develop sooner when individuals are hyperthermic relative to normothermic. This is due, in part, to a large displacement of blood to the cutaneous circulation during hyperthermia, coupled with inadequate cutaneous vasoconstriction during the hypotensive challenge. The influence of local skin temperature on these cutaneous vasoconstrictor responses is unclear. This project tested the hypothesis that local skin temperature modulates cutaneous vasoconstriction during simulated haemorrhage in hyperthermic humans. Eight healthy participants (four men and four women; 32 ± 7 years old; 75.2 ± 10.8 kg) underwent lower-body negative pressure to presyncope while heat stressed via a water-perfused suit sufficiently to increase core temperature by 1.2 ± 0.2 °C. At forearm skin sites distal to the water-perfused suit, local skin temperature was either 35.2 ± 0.6 (mild heating) or 38.2 ± 0.2 °C (moderate heating) throughout heat stress and lower-body negative pressure, and remained at these temperatures until presyncope. The reduction in cutaneous vascular conductance during the final 90 s of lower-body negative pressure, relative to heat-stress baseline, was greatest at the mildly heated site (-10 ± 15% reduction) relative to the moderately heated site (-2 ± 12%; P = 0.05 for the magnitude of the reduction in cutaneous vascular conductance between sites), because vasoconstriction at the moderately heated site was either absent or negligible. In hyperthermic individuals, the extent of cutaneous vasoconstriction during a simulated haemorrhage can be modulated by local skin temperature. In situations where skin temperature is at least 38 °C, as is the case in soldiers operating in warm climatic conditions, a haemorrhagic insult is unlikely to be accompanied by cutaneous vasoconstriction.