Role of N-Methyl-D-Aspartate and Non-N-Methyl-D-Aspartate Receptors in the Cardiovascular Effects of L-Glutamate Microinjection Into the Hypothalamic Paraventricular Nucleus of Unanesthetized Rats

We report on the cardiovascular effects of L-glutamate (L-glu) microinjection into the hypothalamic paraventricular nucleus (PVN) as well as the mechanisms involved in their mediation. L-glu microinjection into the PVN caused dose-related pressor and tachycardiac responses in unanesthetized rats. These responses were blocked by intravenous (i.v.) pretreatment with the ganglion blocker pentolinium (PE; 5 mg/kg), suggesting sympathetic mediation. Responses to L-glu were not affected by local microinjection of the selective non-NMDA receptor antagonist NBQX (2 nmol) or by local microinjection of the selective NMDA receptor antagonist LY235959 (LY; 2 nmol). However, the tachycardiac response was changed to a bradycardiac response after treatment with LY235959, suggesting that NMDA receptors are involved in the L-glu heart rate response. Local pretreatment with LY235959 associated with systemic PE or dTyr(CH(2))(5)(Me)AVP (50 mu g/kg) respectively potentiated or blocked the response to L-glu, suggesting that L-glu responses observed after LY235959 are vasopressin mediated. The increased pressor and bradycardiac responses observed after LY + PE was blocked by subsequent i.v. treatment with the V(1)-vasopressin receptor antagonist dTyr(CH(2))(5)(Me)AVP, suggesting vasopressin mediation. The pressor and bradycardiac response to L-glu microinjection into the PVN observed in animals pretreated with LY + PE was progressively inhibited and even blocked by additional pretreatment with increasing doses of NBQX (2, 10, and 20 nmol) microinjected into the PVN, suggesting its mediation by local non-NMDA receptors. In conclusion, results suggest the existence of two glutamatergic pressor pathways in the PVN: one sympathetic pathway that is mediated by NMDA receptors and a vasopressinergic pathway that is mediated by non-NMDA receptors. (C) 2009 Wiley-Liss, Inc.

Cardiovascular effects of L-glutamate injected in the medial prefrontal cortex of spontaneously hypertensive rats

We have previously reported that L-glutamate (L-glu) injected into the ventral portion of medial prefrontal cortex (vMPFC) of unanesthetized normotensive Wistar rats elicited cardiovascular responses. In the present study we investigated whether the spontaneously hypertensive rat (SHR) exhibit abnormal cardiovascular responses after L-glu microinjection in the vMPFC. Microinjections of L-glu (3, 9, 27, 81 or 150 nmol/200 nl) caused long-lasting dose-related depressor and bradycardiac responses in unanesthetized SHR (n = 6, each dose). Pressor and tachycardiac responses were evoked after the injection of 81 nmol of L-glu in the vMPFC of normotensive Wistar rats (n=6). Systemic pretreatment with the betal-adrenoceptor antagonist atenolol (1.5 mg/kg, i.v.) had no effect on L-glu cardiovascular responses evoked in the SHR (n=5). However, the treatment with the muscarinic antagonist homatropine methyl bromide (I mg/kg, i.v.) blocked the bradycardiac response to L-glu, without significant effects on depressor response evoked by L-glu in the SHR (n = 5). These results indicate that the bradycardiac response to the injection of L-glu injection in the vMPFC is due to activation of the parasympathetic system and not to inhibition of the cardiac sympathetic input. In conclusion, results indicate opposite cardiovascular responses when L-glu was microinjected in the vMPFC of unanesthetized SHR or normotensive. The bradycardiac response observed in the SHR was due to parasympathetic activation and was not affected by pharmacological blockade of the cardiac sympathetic output. (C) 2007 Elsevier B.V. All rights reserved.

The ventrolateral periaqueductal gray is involved in the cardiovascular response evoked by L-glutamate microinjection into the lateral hypothalamus of anesthetized rats

Microinjection Of L-glutamate (L-glu: 1, 3, 10 and 30nmol/100nL) into the lateral hypothalamus (LH) caused dose-related depressor and bradycardiac responses. The cardiovascular response to L-glu stimulation of the LH was blocked by pretreatment of the ventrolateral portion of the periaqueductal gray matter (vIPAG) with CoCl(2) (1 mM/100nL), indicating the existence of a synaptic relay of the hypotensive pathway in that area. Furthermore, the response to L-glu Was blocked by pretreatment of the vIPAG with 2 nmol/100 nL of the selective NMDA-receptor antagonist LY235959 and was not affected by pretreatment with 2 nmol/100 nL of the selective non-NMDA-receptor antagonist NBQX, suggesting a mediation of the hypotensive response by NMDA receptors in the APAG. In conclusion, our results indicate that the hypotensive pathway activated by microinjection Of L-glu into the LH involves a NMDA synaptic relay in the vIPAG. (c) 2007 Elsevier Ireland Ltd. All rights reserved.

Hemodynamic responses to aortic depressor nerve stimulation in conscious L-NAME-induced hypertensive rats

Durand MT, Castania JA, Fazan R Jr, Salgado MC, Salgado HC. Hemodynamic responses to aortic depressor nerve stimulation in conscious L-NAME-induced hypertensive rats. Am J Physiol Regul Integr Comp Physiol 300: R418-R427, 2011. First published November 24, 2010; doi: 10.1152/ajpregu.00463.2010.-The present study investigated whether baroreflex control of autonomic function is impaired when there is a deficiency in NO production and the role of adrenergic and cholinergic mechanisms in mediating reflex responses. Electrical stimulation of the aortic depressor nerve in conscious normotensive and nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats was applied before and after administration of methylatropine, atenolol, and prazosin alone or in combination. The hypotensive response to progressive electrical stimulation (5 to 90 Hz) was greater in hypertensive (-27 +/- 2 to -64 +/- 3 mmHg) than in normotensive rats (-17 +/- 1 to -46 +/- 2 mmHg), whereas the bradycardic response was similar in both groups (-34 +/- 5 to -92 +/- 9 and -21 +/- 2 to -79 +/- 7 beats/min, respectively). Methylatropine and atenolol showed no effect in the hypotensive response in either group. Methylatropine blunted the bradycardic response in both groups, whereas atenolol attenuated only in hypertensive rats. Prazosin blunted the hypotensive response in both normotensive (43%) and hypertensive rats (53%) but did not affect the bradycardic response in either group. Prazosin plus angiotensin II, used to restore basal arterial pressure, provided hemodynamic responses similar to those of prazosin alone. The triple pharmacological blockade abolished the bradycardic response in both groups but displayed similar residual hypotensive response in hypertensive (-13 +/- 2 to -27 +/- 2 mmHg) and normotensive rats (-10 +/- 1 to -25 +/- 3 mmHg). In conclusion, electrical stimulation produced a well-preserved baroreflex-mediated decrease in arterial pressure and heart rate in conscious L-NAME-induced hypertensive rats. Moreover, withdrawal of the sympathetic drive played a role in the reflex bradycardia only in hypertensive rats. The residual fall in pressure after the triple pharmacological blockade suggests the involvement of a vasodilatory mechanism unrelated to NO or deactivation of alpha(1)-adrenergic receptor.

Atrial stretch increases the gastric tonus of anesthetized rats

Aims: We assessed the effects of right atrial stretch on gastric tone and neuro-humoral pathways involved in this phenomenon. Main methods: Anesthetized male rats were submitted for monitoring of the mean arterial pressure (MAP) and central venous pressure (CVP). A balloon catheter positioned into the stomach monitored by plethysmography the gastric volume (GV). All rats were monitored for 55-min. After the first 20-min of monitoring (basal period), rats were either submitted to a 5-min interval of atrial stretch (AS) or maintained as controls. An intra-atrial balloon catheter was distended with 30,50, or 70 mu L of saline. GV and hemodynamic data were also monitored for a further 30-min. Another set of rats, either previously submitted to subdiaphragmaic vagotomy or splanchnicectomy plus celiac ganglionectomy or maintained as controls (sham), were also submitted to AS. Each subset consisted of six rats. The plasma level of the atrial natriuretic peptide (ANP) was measured in another group of rats. Data were compared by ANOVA followed by Bonferroni`s test. Key findings: In control rats, the GV, MAP, and CVP remained at stable levels throughout the studies. In addition to increase the CVP, AS also decreased (P<0.05) the GV by 14%, 11.5%, and 16.5% in the 30, 50, and 70 mu L groups, respectively. Vagotomy prevented the GV decrease. In contrast, the AS decreased (P<0.05) the GV by 21.3% in splanchnicectomized rats. Significance: AS decreased the GV of rats in a volume-dependent manner, a phenomenon prevented by vagotomy but enhanced by celiac ganglionectomy. (C) 2010 Elsevier Inc. All rights reserved.

Sympathetic activity is not increased in L-NAME hypertensive rats

Santos FM, Dias DPM, Silva CAA, Fazan Jr R, Salgado HC. Sympathetic activity is not increased in L-NAME hypertensive rats. Am J Physiol Regul Integr Comp Physiol 298: R89-R95, 2010. First published November 4, 2009; doi:10.1152/ajpregu.00449.2009.-The role played by the sympathetic drive in the development of N(G)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension is not firmly established. Therefore, the present study was undertaken in conscious rats in which hypertension was induced by treatment with L-NAME over the course of either 2 or 14 days. Mean arterial pressure (MAP) was measured via a catheter placed in the femoral artery, drugs were administered via a cannula placed in the femoral vein, and renal sympathetic nerve activity (RSNA) was monitored using an implanted electrode. Despite the remarkable increase in arterial pressure, heart rate did not change after treatment with L-NAME. RSNA was similar in L-NAME-induced hypertensive rats treated over the course of 2 or 14 days, as well as in normotensive rats. It was also demonstrated that L-NAME-induced hypertensive rats displayed a resetting of the baroreflex control of RSNA to hypertensive levels, with decreased sensitivity over the course of 2 or 14 days. Furthermore, the sympathetic-vagal balance examined in the time and frequency domain and the renal and plasma norepinephrine content did not differ between groups. In conclusion, the evaluation of the sympathetic drive in conscious rats demonstrated that the arterial hypertension induced by L-NAME treatment over the course of 2 and 14 days does not show sympathetic overactivity.

Are l-glutamate and ATP cotransmitters of the peripheral chemoreflex in the rat nucleus tractus solitarius ?

Peripheral chemoreflex activation in awake rats or in the working heart-brainstem preparation (WHBP) produces sympathoexcitation, bradycardia and an increase in the frequency of phrenic nerve activity. Our focus is the neurotransmission of the sympathoexcitatory component of the chemoreflex within the nucleus of the tractus solitarius (NTS), and recently we verified that the simultaneous antagonism of ionotropic glutamate and purinergic P(2) receptors in the NTS blocked the pressor response and increased thoracic sympathetic activity in awake rats and WHBP, respectively, in response to peripheral chemoreflex activation. These previous data suggested the involvement of ATP and L-glutamate in the NTS in the processing of the sympathoexcitatory component of the chemoreflex by unknown mechanisms. For a better understanding of these mechanisms, here we used a patch-clamp approach in brainstem slices to evaluate the characteristics of the synaptic transmission of NTS neurons sending projections to the ventral medulla, which include the premotor neurons involved in the generation of the sympathetic outflow. The NTS neurons sending projections to the ventral medulla were identified by previous microinjection of the membrane tracer dye, 1,1`-dioctadecyl-3,3,3`,3`-tetramethylindocarbocyanine perchlorate (DiI), in the ventral medulla and the spontaneous (sEPSCs) and tractus solitarius (TS)-evoked excitatory postsynaptic current (TS-eEPSCs) were recorded using patch clamp. With this approach, we made the following observations on NTS neurons projecting to the ventral medulla: (i) the sEPSCs and TS-eEPSCs of DiI-labelled NTS neurons were completely abolished by 6,7-dinitroquinoxaline-2,3(1H,4H)-dione (DNQX), an antagonist of ionotropic non-NMDA glutamatergic receptors, showing that they are mediated by L-glutamate; (ii) application of ATP increased the frequency of appearance of spontaneous glutamatergic currents, reflecting an increased exocytosis of glutamatergic vesicles; and (iii) ATP decreased the peak of TS-evoked glutamatergic currents. We conclude that L-glutamate is the main neurotransmitter of spontaneous and TS-evoked synaptic activities in the NTS neurons projecting to the ventral medulla and that ATP has a dual modulatory role on this excitatory transmission, facilitating the spontaneous glutamatergic transmission and inhibiting the TS-evoked glutamatergic transmission. These data also suggest that ATP is not acting as a cotransmitter with L-glutamate, at least at the level of this subpopulation of NTS neurons studied.

Modulation of respiratory responses to chemoreflex activation by L-glutamate and ATP in the rostral ventrolateral medulla of awake rats

Moraes DJA, Bonagamba LGH, Zoccal DB, Machado BH. Modulation of respiratory responses to chemoreflex activation by L-glutamate and ATP in the rostral ventrolateral medulla of awake rats. Am J Physiol Regul Integr Comp Physiol 300: R1476-R1486, 2011. First published March 16, 2011; doi:10.1152/ajpregu.00825.2010.-Presympathetic neurons in the different anteroposterior aspects of rostral ventrolateral medulla (RVLM) are colocalized with expiratory [Botzinger complex (BotC)] and inspiratory [pre-Botzinger complex (pre-BotC)] neurons of ventral respiratory column (VRC), suggesting that this region integrates the cardiovascular and respiratory chemoreflex responses. In the present study, we evaluated in different anteroposterior aspects of RVLM of awake rats the role of ionotropic glutamate and purinergic receptors on cardiorespiratory responses to chemoreflex activation. The bilateral ionotropic glutamate receptors antagonism with kynurenic acid (KYN) (8 nmol/50 nl) in the rostral aspect of RVLM (RVLM/BotC) enhanced the tachypneic (120 +/- 9 vs. 180 +/- 9 cpm; P < 0.01) and attenuated the pressor response (55 +/- 2 vs. 15 +/- 1 mmHg; P < 0.001) to chemoreflex activation (n = 7). On the other hand, bilateral microinjection of KYN into the caudal aspect of RVLM (RVLM/pre-BotC) caused a respiratory arrest in four awake rats used in the present study. Bilateral P2X receptors antagonism with PPADS (0.25 nmol/50 nl) in the RVLM/BotC reduced chemoreflex tachypneic response (127 +/- 6 vs. 70 +/- 5 cpm; P < 0.001; n = 6), but did not change the chemoreflex pressor response. In addition, PPADS into the RVLM/BtC attenuated the enhancement of the tachypneic response to chemoreflex activation elicited by previous microinjections of KYN into the same subregion (188 +/- 2 vs. 157 +/- 3 cpm; P < 0.05; n = 5). Our findings indicate that: 1) L-glutamate, but not ATP, in the RVLM/BtC is required for pressor response to peripheral chemoreflex and 2) both transmitters in the RVLM/BtC are required for the processing of the ventilatory response to peripheral chemoreflex activation in awake rats.

Antimicrobial Activities of Ethanol Extract and Coumestans from Eclipta alba (L.) Hassk (Asteraceae)

Ethanol extract and fractions from aerial parts of Eclipta alba (L.) Hassk (Asteraceae) were screened for the antibacterial and antifungal activities against different species of human pathogenic bacterial ATCC, antibiotic-resistant clinical isolates and strains of the dermatophyte Trichophyton rubrum (wild and mutant for TruMDR2 gene) using a microdilution method. Demethylwedelolactone/wedelolactone (DWL/WL) and only wedelolactone (WL), both in a high homogeneity degree, were efficient to inhibit the ATCC strains of Staphylococus aureus (Minimal Inhibitory Concentration MIC = 75 mu g/mL), Staphylococcus epidemidis (MIC = 125 mu g/mL) and Escherichia coli (MIC = 125 mu g/mL) as well as antibiotic-resistant clinical isolates of Enterococcus spp (MIC = 250 mu g/mL) and S. aureus (MIC = 125 mu g/mL). Ethanol extract was more effective than the purified fractions against Trichophyton rubrum strains (MIC = 125 mu g/mL), suggesting that anti-fungal activity is not only related to demethylwedelolactone and wedelolactone, but also to a synergistic action between these coumestans and other compounds found in that extract. Thus, this work suggests that E. alba possesses a significant antimicrobial activity, including that against multi-drug resistant microorganisms, which could be of relevance for the treatment of infectious diseases.

Differential effects of coffee on the risk of type 2 diabetes according to meal consumption in a French cohort of women: the E3N/EPIC cohort study

Background: Coffee consumption has been associated with a lower risk of diabetes, but little is known about the mechanisms responsible for this association, especially related to the time when coffee is consumed. Objective: We examined the long-term effect of coffee, globally and according to the accompanying meal, and of tea, chicory, and caffeine on type 2 diabetes risk. Design: This was a prospective cohort study including 69,532 French women, aged 41-72 y from the E3N/EPIC (Etude Epidemiologique aupres de Femmes de la Mutuelle Generale de l`Education Nationale/European Prospective Investigation into Cancer and Nutrition) cohort study, without diabetes at baseline. Food and drink intakes per meal were assessed by using a validated diet-history questionnaire in 1993-1995. Results: During a mean follow-up of 11 y, 1415 new cases of diabetes were identified. In multivariable Cox regression models, the hazard ratio in the highest category of coffee consumption [>= 3 cups (375 mL)/d] was 0.73 (95% CI: 0.61, 0.87; P for trend < 0.001), in comparison with no coffee consumption. This inverse association was restricted to coffee consumed at lunchtime (hazard ratio: 0.66; 95% CI: 0.57, 0.76) when comparing >1.1 cup (125 mL)/meal with no intake. At lunchtime, this inverse association was observed for both regular and decaffeinated coffee and for filtered and black coffee, with no effect of sweetening. Total caffeine intake was also associated with a statistically significantly lower risk of diabetes. Neither tea nor chicory consumption was associated with diabetes risk. Conclusions: Our data support an inverse association between coffee consumption and diabetes and suggest that the time of drinking coffee plays a distinct role in glucose metabolism. Am J Clin Nutr 2010; 91: 1002-12.

Occult risk factor for the development of cerebral edema in children with diabetic ketoacidosis: possible role for stomach emptying

The incidence of cerebral edema during therapy of diabetic ketoacidosis (DKA) in children remains unacceptably high-this suggests that current treatment may not be ideal and that important risk factors for the development of cerebral edema have not been recognized. We suggest that there are two major sources for an occult generation of osmole-free water in these patients: first, fluid with a low concentration of electrolytes that was retained in the lumen of the stomach when the patient arrived in hospital; second, infusion of glucose in water at a time when this solution can be converted into water with little glucose. In a retrospective chart review of 30 patients who were admitted with a diagnosis of DKA and a blood sugar > 900 mg/dL (50 mmol/L), there were clues to suggest that some of the retained fluid in the stomach was absorbed. To minimize the likelihood of creating a dangerous degree of cerebral edema in patients with DKA, it is important to define the likely composition of fluid retained in the stomach on admission, to look for signs of absorption of some of this fluid during therapy, and to be especially vigilant once fat-derived brain fuels have disappeared, because this is the time when glucose oxidation in the brain should increase markedly, generating osmole-free water.

Aluminum Concentrations in Water of Elderly People`s Houses and Retirement Homes and Its Relation with Elderly Health

The purpose of this study was to determine the concentrations of aluminum (Al) and other metals in water samples from elderly people`s houses and retirement homes. Forty-six duplicate water samples from kitchen taps were collected in Ribeiro Preto/SP, Brazil. Metal levels were measured by atomic absorption spectrophotometer. Aluminum concentration exceeded the maximum allowed values in 26% of samples according to the Decree 518/2004 of the Brazilian Health Ministry. It was noted that 11% of elderly living at monitored houses, as well as 19% living at retirement homes presented Alzheimer disease diagnostic. These results suggest taking into account Al risks among vulnerable elderly population groups.

Postembryonic Development of Rectal Pads in Bees (Hymenoptera, Apidae)

The morphology and development of the digestive tract of insects has been extensively studied, but little attention has been given to the development of the rectal pads. These organs are responsible for absorption of water and salts. In insects where they occur, there are usually six ovoid rectal pads located in the medial-anterior portion of the rectum. The rectal pad has three types of cells: principal, basal, and junctional. The arrangement of these three cell types delimits an intrapapillary lumen. The aim of the current study is to describe the development of the rectal pads during postembryonic development of Melipona quadrifasciata anthidioides and Melipona scutellaris. Specimens were analyzed at the following developmental stages: white-, pink-, brown-, and black-eyed pupae, and adult workers. The development of the rectal pad begins as a thickening of the epithelium in white-eyed pupae at 54 hr. At this stage, there is neither a basal cell layer nor intrapapillary lumen. The basal layers begin to form in the pink-eyed pupa and are completely formed at the end of the development of the brown-eyed pupa. In the brown-eyed pupal stage, the intrapapillary lumen is formed and the junctional cells are positioned and completely differentiated. Necrotic and apoptotic cell death were detected along with cell proliferation in the whole rectum during pupal development, suggesting that the development of the rectal pads involves cell proliferation, death, and differentiation. The rectal pads originate only from the ectoderm. Anat Rec, 292:1602-1611, 2009. (C) 2009 Wiley-Liss, Inc.

Antidepressant-like effects of N-acetyl-L-cysteine in rats

Oxidative stress disturbances have been reported in depressed patients and in animals submitted to stress. Recent evidence suggests that antidepressants may have antioxidant properties. However, the therapeutic potential of antioxidants as antidepressant drugs has not been systematically investigated. Therefore, this study tested the hypothesis that N-acetyl-L-cysteine (NAC), a cysteine prodrug with powerful antioxidant activity, would possess anti depressant-like properties in the forced swimming test. Male Wistar rats were subjected to 15 min of forced swimming and immediately afterward, 5, and 23 h later received intraperitoneal injections of NAC (5, 15, 50, 150, and 250 mg/kg), imipramine, 0 5 mg/kg) or vehicle. One hour later they were submitted to the 5 min test swimming session, where immobility time was recorded. Independent groups of animals received the same treatments and their exploratory activity was measured in an open arena for 5 min. NAC (at the doses of 15, 50, and 150 mg/kg) and imipramine induced a significant decrease in immobility time without changing exploratory behavior measured in an open arena. These results suggest that antioxidants such as NAC may have antidepressant effects. Behavioural Pharmacology (C) 19:747-750 2008 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.