Effects of Psidium guajava L. leaves extract on blood pressure control and IL-10 production in salt-dependent hypertensive rats.

Psidium guajava (guava) leaves extract displays anti-hypertensive properties by mechanisms not yet fully understood. Here, we investigated whether sympathetic drive and immune signaling mechanisms are involved with the antihypertensive effect of the guava extract in a model of salt-dependent hypertension. Raw guava extract (rPsE) was characterized by colorimetric and UPLC-MS techniques. Two doses of rPsE (100 and 200 mg/kg) were evaluated for anti-hypertensive effect using a suspension system (PsE). Weaned male Wistar rats were put on a high-salt diet (HSD, 0.90 % Na+) for 16 weeks and received gavages of PsE for the last 4 weeks. Blood pressure (BP) was measured at the end of treatment in conscious rats. The neurogenic pressor effect was assessed by ganglionic blockade with hexamethonium. Autonomic modulation of heart rate was evaluated by spectral analysis. The effects of orally administered PsE on lumbar sympathetic nerve activity (LSNA) were assessed in anesthetized rats. Blood IL-10, IL-17A, and TNF were measured. The increased neurogenic pressor effect of HSD rats was reduced by PsE 100 mg/kg, but not by 200 mg/kg. PsE (200 mg/kg) administration in anesthetized rats produced a greater fall in BP of HSD rats compared to standard salt diet (SSD) rats. PsE hypotensive response elicited an unproportionable increase in LSNA of HSD rats compared to SSD rats. PsE (200 mg/kg) increased plasma concentrations of IL-10 but had no effect on TNF or IL-17A. Our data indicate that the antihypertensive effects of PsE may involve autonomic mechanisms and immunomodulation by overexpression of IL-10 in salt-dependent hypertensive rats.

Chronic high-sodium diet intake after weaning lead to neurogenic hypertension in adult Wistar rats.

In this study, we investigated some mechanisms involved in sodium-dependent hypertension of rats exposed to chronic salt (NaCl) intake from weaning until adult age. Weaned male Wistar rats were placed under high (0.90% w/w, HS) or regular (0.27% w/w, Cont) sodium diets for 12 weeks. Water consumption, urine output and sodium excretion were higher in HS rats compared to control. Blood pressure (BP) was directly measured by the arterial catheter and found 13.8% higher in HS vs Cont rats. Ganglionic blockade with hexamethonium caused greater fall in the BP of HS rats (33%), and central antagonism of AT1 receptors (losartan) microinjected into the lateral ventricle reduced BP level of HS, but not of Cont group. Heart rate variability analysis revealed sympathetic prevalence on modulation of the systolic interval. HS diet did not affect creatinine clearance. Kidney histological analysis revealed no significant change in renal corpuscle structure. Sodium and potassium concentrations in CSF were found higher in HS rats despite no change in plasma concentration of these ions. Taken together, data suggest that animals exposed to chronic salt intake to a level close to that reported for human' diet since weaning lead to hypertension, which appears to rely on sodium-driven neurogenic mechanisms.

Striking antitumor activity of a methinium system with incorporated quinoxaline unit obtained by spontaneous cyclization.

A novel pentamethinium salt was synthesized with an unforeseen expanded conjugated quinoxaline unit directly incorporated into a pentamethinium chain. The compound exhibited high fluorescence intensity, selective mitochondrial localization, high cytotoxicity, and selectivity toward malignant cell lines, and resulted in remarkable in vivo suppression of tumor growth in mice.

Artemin growth factor increases nicotinic cholinergic receptor subunit expression and activity in nociceptive sensory neurons.

BACKGROUND: Artemin (Artn), a member of the glial cell line-derived growth factor (GDNF) family, supports the development and function of a subpopulation of peptidergic, TRPV1-positive sensory neurons. Artn (enovin, neublastin) is elevated in inflamed tissue and its injection in skin causes transient thermal hyperalgesia. A genome wide expression analysis of trigeminal ganglia of mice that overexpress Artn in the skin (ART-OE mice) showed elevation in nicotinic acetylcholine receptor (nAChR) subunits, suggesting these ion channels contribute to Artn-induced sensitivity. Here we have used gene expression, immunolabeling, patch clamp electrophysiology and behavioral testing assays to investigate the link between Artn, nicotinic subunit expression and thermal hypersensitivity. RESULTS: Reverse transcriptase-PCR validation showed increased levels of mRNAs encoding the nAChR subunits α3 (13.3-fold), ß3 (4-fold) and ß4 (7.7-fold) in trigeminal ganglia and α3 (4-fold) and ß4 (2.8-fold) in dorsal root ganglia (DRG) of ART-OE mice. Sensory ganglia of ART-OE mice had increased immunoreactivity for nAChRα3 and exhibited increased overlap in labeling with GFRα3-positive neurons. Patch clamp analysis of back-labeled cutaneous afferents showed that while the majority of nicotine-evoked currents in DRG neurons had biophysical and pharmacological properties of α7-subunit containing nAChRs, the Artn-induced increase in α3 and ß4 subunits resulted in functional channels. Behavioral analysis of ART-OE and wildtype mice showed that Artn-induced thermal hyperalgesia can be blocked by mecamylamine or hexamethonium. Complete Freund's adjuvant (CFA) inflammation of paw skin, which causes an increase in Artn in the skin, also increased the level of nAChR mRNAs in DRG. Finally, the increase in nAChRs transcription was not dependent on the Artn-induced increase in TRPV1 or TRPA1 in ART-OE mice since nAChRs were elevated in ganglia of TRPV1/TRPA1 double knockout mice. CONCLUSIONS: These findings suggest that Artn regulates the expression and composition of nAChRs in GFRα3 nociceptors and that these changes contribute to the thermal hypersensitivity that develops in response to Artn injection and perhaps to inflammation.

Analgesic and anti-inflammatory effects of honey: the involvement of autonomic receptors.

The use of honey for therapeutic purposes is on the increase and many studies have shown that honey has the ability to influence biological systems including pain transmission. Therefore, this study was designed to investigate the analgesic and anti-inflammatory effects of honey and the effects of concurrent administration of autonomic nervous system blocking drugs. Studies on analgesic activities was carried out using hotplate and formalin-induced paw licking models while the anti-inflammatory activity was by the carrageenan paw oedema method. Animals were distributed into six groups consisting of five animals each. They were administered saline, honey (600 mg/kg), indomethacin (5 mg/kg), autonomic blockers (3 µg/kg of tamsulosin, 20 mg/kg (intraperitoneally) of propranolol, 2 ml/kg of atropine or 10 mg/kg (intra muscularly) of hexamethonium) or honey (200 and 600 mg/kg) with one of the blockers. The results showed that honey reduced pain perception especially inflammatory pain and the administration of tamsulosin and propranolol spared the effect of honey. Hexamethonium also spared the effects of honey at the early and late phases of the test while atropine only inhibited the early phase of the test. However, atropine and hexamethonium spared the anti-inflammatory effects of honey but tamsulosin abolished the effects while propranolol only abolished the anti-inflammatory effects at the peak of the inflammation. The results suggest the involvement of autonomic receptors in the anti-nociceptive and anti-inflammatory effects of honey although the level of involvement depends on the different types of the receptors.

Neuronal nicotinic receptor antagonist reduces anxiety-like behavior in mice.

Brain cholinergic neurotransmission has been implicated in the modulation of anxiety in humans and evidence suggests that drugs targeting neuronal nicotinic acetylcholine receptor (nAChR) could have potential for the treatment of anxiety. The objective of present study was to examine anxiolytic effects of lobeline (0.04 or 0.1 mg/kg), a nAChR antagonist, in C57BL/6J mice using elevated plus-maze (EPM) and marble-burying test. Lobeline (0.04 mg/kg) significantly increased open arm time on EPM and reduced number of marbles buried. Similarly, mecamylamine (0.3 mg/kg) produced anxiolytic effects, while peripherally acting hexamethonium (0.3 mg/kg) failed to produce any response. These results provide evidence that lobeline has anxiolytic potential and nAChR antagonists may represent a new class of anxiolytics in humans.

Post-resistance exercise hypotension in spontaneously hypertensive rats is mediated by nitric oxide.

1. Postexercise hypotension (PEH) plays an important role in the non-pharmacological treatment of hypertension. It is characterized by a decrease in blood pressure (BP) after a single bout of exercise in relation to pre-exercise levels. 2. The present study investigated the effect of a single session of resistance exercise, as well as the effect of nitric oxide (NO) and the autonomic nervous system (ANS), in PEH in spontaneously hypertensive rats (SHR). 3. Catheters were inserted into the left carotid artery and left jugular vein of male SHR (n = 37) for the purpose of measuring BP or heart rate (HR) and drug or vehicle administration, respectively. Haemodynamic measurements were made before and after acute resistance exercise. The roles of NO and the ANS were investigated by using N(G)-nitro-L-arginine methyl ester (L-NAME; 15 mg/kg, i.v.) and hexamethonium (20 mg/kg, i.v.) after a session of acute resistance exercise. 4. Acute resistance exercise promoted a pronounced reduction in systolic and diastolic BP (-37 +/- 1 and -8 +/- 1 mmHg, respectively; P < 0.05), which was suppressed after treatment with L-NAME. The reduction in systolic BP caused by exercise (-37 +/- 1 mmHg) was not altered by the administration of hexamethonium (-38 +/- 2 mmHg; P > 0.05). After exercise, the decrease in diastolic BP was greater with hexamethonium (-26 +/- 1 mmHg; P < 0.05) compared with the decrease caused by exercise alone. 5. The results suggest that acute resistance exercise has an important hypotensive effect on SHR and that NO plays a crucial role in this response.

Nitric oxide dependent vasodilation in young spontaneously hypertensive rats.

Conflicting evidence exists on the possible impairment of tonic nitric oxide (NO) mediated vasodilation as a causative factor in the genesis of human as well as experimental hypertension. We evaluated the tonic NO-dependent vasodilation from the pressor response to NO synthesis inhibition by NG-monomethyl-L-arginine (L-NMMA) in 9 conscious, chronically instrumented spontaneously hypertensive rats (SHR) at 12 weeks of age, ie, during the early established hypertensive stage. Nine age-matched Wistar-Kyoto rats (WKY) were used as controls. The pressor responses to L-NMMA (100 mg . kg-1 IV bolus plus 1.5 mg . kg-1 . min-1 infusion for 60 minutes) as well as to non NO-dependent pressor stimuli, namely, vasopressin (2, 4, and 8 ng . kg-1) and phenylephrine (0.5, 1, and 2 microg . kg-1) given as IV boluses, were assessed both under control conditions and during suppression of autonomic reflexes by hexamethonium (30 mg . kg-1 IV bolus+1.5 mg . kg-1 . min-1 infusion). Rather than being reduced, the pressor responses to L-NMMA were 39% and 71% larger in the control and areflexic conditions, respectively, than those observed in WKY (both P<0.01). A similar pattern was observed for the pressor responses to vasopressin (+37% and +68% in the control and areflexic conditions, respectively; both P<0.01) and phenylephrine, (+20% and +52%; both P<0.05). Additional groups of 6-week-old prehypertensive SHR (n=11) and age-matched WKY (n=11) were subjected to an identical protocol: in these animals, the pressor responses to L-NMMA were similar in each strain, as were the pressor responses to vasopressin and phenylephrine in both control and areflexic conditions. In conclusion, our observations indicate that during the developmental phase of hypertension in the SHR model, namely, during the prehypertensive as well as the early established hypertensive stage, NO-dependent vasodilation is preserved (if not enhanced) so that a putative impairment of this function provides no significant pathogenic contribution to the onset of hypertension in this experimental model.

Tetanic fade induced by d-Tubocurarine, Hexamethonium and Neostigmine in phrenic nerve diaphragm rats

A acetilcolina liberada do terminal nervoso motor (TNM) pode modular sua pr6pria liberagdo (automodulação do TNM), interagindo com receptores nicotinicos (autoestimulação do TNM) ou muscarinicos (autoinibição do TNM) pré-juncionais. Por outro lado, tem-se demonstrado que a neuropatia induzida pelo estado diabético determine vários danos estruturais no interior do TNM, sem, contudo, interferir na velocidade e na integridade da transmissão neuromuscular. Estudos farmacológicos demonstram que animais diabéticos, quando comparados aos normais, são menos sensíveis a alguns bloqueadores neuromusculares (d-tubocurarina, galamina, pancurônio e decametônio). Esses resultados sugerem que alguma modificação no sistema de automodulação do TNM pode contrabalançar as deficiências neuronais induzidas pelo estado diabético. Dessa forma, o presente estudo foi conduzido com preparações nervo frênico-diafragma isolado de ratos (obtidas de animais normais e diabéticos) na tentativa de verificar se existiriam diferenças na fadiga neuromuscular induzida por drogas (d-tubocurarina, neostigmina, hexametônio). Nossos resultados mostraram que, embora não existissem diferenças na indução da fadiga neuromuscular induzida por d-tubocurarina, neostigmina ou hexametônio, o recobro da fadiga neuromuscular induzida por d-tubocurarina foi mais rápido em preparações neuromusculares obtidas de animais diabéticos. Essa diferença pode estar relacionada a alguma modificação induzida pelo estado diabético que determinou redugio da afinidade da d-tubocurarina para os receptores nicotínicos pré-juncionais

Small-bowel obstruction and the effects of lidocaine, atropine and hexamethonium on inflammation and fluid losses.

BACKGROUND: The profuse fluid losses and morbidity of patients suffering from obstructive ileus are closely related to inflammatory changes in the obstructed bowel wall. Previous experimental studies have shown that use of steroids and NSAIDs can reduce fluid losses in obstructive ileus. In the present study, we investigated the effects of lidocaine on fluid losses since local anesthetics have been shown to possess wide and potent anti-inflammatory properties. Hexamethonium and atropine were used to study the importance of the autonomic nervous system in bowel obstruction. METHOD: Experiments were performed in rats in vivo. After 18 h of total obstruction of the jejunum by thread ligation, a segment of the obstructed jejunum was placed in a chamber with intact nervous and vascular supply and net fluid transport was continuously registered by a gravimetric technique. Extravasation of Evans blue albumin as marker of inflammation was quantified by spectrophotometry. RESULTS: Hexamethonium (10 mg.kg-1 i.v.) significantly inhibited net fluid secretion (P < .05), while atropine (0.25 mg.kg-1 i.v.) had no significant effect. Net fluid secretion was reversed into absorption following an intravenous bolus dose of lidocaine (2 mg.kg-1) (P < 0.01) and topical administration of lidocaine (20 mg) on the serosa of the obstructed gut (P < 0.01). Single topical administration of lidocaine (20 mg) immediately before ligation significantly reduced net fluid secretion (P < 0.05) and inflammation (P < 0.05) in the obstructed bowel 20 h post-ligation compared to obstructed controls. CONCLUSION: Lidocaine significantly inhibited or prevented fluid losses when administered intravenously or topically to the obstructed gut. Mechanisms of action could be inhibition of nerve reflexes involved in fluid secretion and by inhibition of inflammation in the bowel wall. The inhibition of fluid losses by hexamethonium further supports the importance of the autonomic nervous system in the pathophysiology of bowel obstruction.

Contribution of the sympathetic nervous system to salt-sensitivity in lifetime captopril-treated spontaneously hypertensive rats.

OBJECTIVE: To test the hypothesis that, in lifetime captopril-treated spontaneously hypertensive rats (SHR), the sympathetic nervous system contributes importantly to the hypertensive effect of dietary sodium chloride supplementation. METHODS: Male SHR (aged 6 weeks) that had been treated from conception onward with either captopril or vehicle remained on a basal sodium chloride diet or were fed a high sodium chloride diet. After 2 weeks, the rats were subjected to ganglionic blockade and 2 days later, an infusion of clonidine. RESULTS: Lifetime captopril treatment significantly lowered mean arterial pressure in both groups. Intravenous infusion of the ganglionic blocker hexamethonium resulted in a rapid decline in MAP that eliminated the dietary sodium chloride-induced increase in MAP in both groups. Infusion of the central nervous system alpha2-adrenergic receptor agonist clonidine also resulted in a greater reduction in MAP in both groups of SHR that were fed the high (compared with the basal) sodium chloride diet. CONCLUSIONS: In both lifetime captopril-treated and control SHR, the sympathetic nervous system contributes to the pressor effects of a high sodium chloride diet.

Pharmacological studies of allergic cough in the guinea pig.

The pharmacological mechanisms of allergic cough in the guinea pig were studied. Actively sensitized guinea pigs were exposed to aerosols of antigen to elicit coughing. In separate experiments, naive guinea pigs were exposed to aerosols of capsaicin to elicit coughing. Both allergic and capsaicin-induced cough were inhibited by loratadine (0.3-10 mg kg-1 p.o.) and chlorpheniramine (0.1-3.0 mg kg-1 p.o.). Neither cimetidine (10 mg kg-1 s.c.), nor thioperamide (3-10 mg kg-1 s.c.), inhibited allergic or capsaicin-induced cough. Codeine (3-30 mg kg-1 p.o.), salbutamol (0.003-3.0 mg kg-1 s.c.) and ipratropium (0.03-1.0 mg kg-1 s.c.) inhibited both allergic and capsaicin-induced cough. Hexamethonium (10 and 30 mg kg-1 s.c.) inhibited allergic, but not capsaicin-induced cough. Allergic and capsaicin-induced cough were unaffected by phenidone (5.0 and 10.0 mg kg-1 s.c.). Indomethacin (5.0 and 10.0 mg kg-1 s.c.) had no effect on allergic cough but slightly inhibited capsaicin-induced cough. We conclude that allergic and capsaicin-induced cough are modulated by histamine H1 receptor and cholinergic mechanisms. Histamine H2 or histamine H3 receptor mechanisms, and lipoxygenase and cyclooxygenase products of arachidonic acid metabolism do not influence allergic and capsaicin-induced cough. Ganglionic mechanisms play a minor role in the production of allergic cough and no role in capsaicin-induced cough.