Exercise and Beta-Glucan Consumption (Saccharomyces cerevisiae) Improve the Metabolic Profile and Reduce the Atherogenic Index in Type 2 Diabetic Rats (HFD/STZ)

Physical activity and the ingestion of dietary fiber are non-drug alternatives commonly used as adjuvants to glycemic control in diabetic individuals. Among these fibers, we can highlight beta-glucans. However, few studies have compared isolated and synergic effects of physical exercise and beta-glucan ingestion, especially in type 2 diabetic rats. Therefore, we evaluated the effects beta-glucan (Saccharomyces cerevisiae) consumption, associated or not to exercise, on metabolic parameters of diabetic Wistar rats. The diabetes mellitus (DM) was induced by high-fat diet (HFD) associated with a low dose of streptozotocin (STZ-35 mg/kg). Trained groups were submitted to eight weeks of exercise in aquatic environment. In the last 28 days of experiment, animals received 30 mg/kg/day of beta-glucan by gavage. Isolated use of beta-glucan decreased glucose levels in fasting, Glycated hemoglobin (HbA1c), triglycerides (TAG), total cholesterol (TC), low-density lipoprotein (LDL-C), the atherogenic index of plasma. Exercise alone also decreased blood glucose levels, HbA1c, and renal lesions. An additive effect for reducing the atherogenic index of plasma and renal lesions was observed when both treatments were combined. It was concluded that both beta-glucan and exercise improved metabolic parameters in type 2 (HFD/STZ) diabetic rats.

Role of the bed nucleus of the stria terminalis in the cardiovascular responses to acute restraint stress in rats

The aim of this work was to test the hypothesis that the bed nucleus of the stria terminalis (BST) and noradrenergic neurotransmission therein mediate cardiovascular responses to acute restraint stress in rats. Bilateral microinjection of the non-specific synaptic blocker CoCl(2) (0.1 nmol/100 nl) into the BST enhanced the heart rate (HR) increase associated with acute restraint without affecting the blood pressure increase, indicating that synapses within the BST influence restraint-evoked HR changes. BST pretreatment with the selective alpha(1)-adrenoceptor antagonist WB4101 (15 nmol/100 nl) caused similar effects to cobalt, indicating that local noradrenergic neurotransmission mediates the BST inhibitory influence on restraint-related HR responses. BST treatment with equimolar doses of the alpha(2)-adrenoceptor antagonist RX821002 or the beta-adrenoceptor antagonist propranolol did not affect restraint-related cardiovascular responses, reinforcing the inference that alpha(1)-adrenoceptors mediate the BST-related inhibitory influence on HR responses. Microinjection of WB4101 into the BST of rats pretreated intravenously with the anticholinergic drug homatropine methyl bromide (0.2 mg/kg) did not affect restraint-related cardiovascular responses, indicating that the inhibitory influence of the BST on the restraint-evoked HR increase could be related to an increase in parasympathetic activity. Thus, our results suggest an inhibitory influence of the BST on the HR increase evoked by restraint stress, and that this is mediated by local alpha(1)-adrenoceptors. The results also indicate that such an inhibitory influence is a result of parasympathetic activation.

Anxiolytic-like effects induced by acute reversible inactivation of the bed nucleus of stria terminalis

There is conflicting evidence concerning the role of the bed nucleus of the stria terminalis (BNST) in fear and anxiety-elicited behavior. Most of the studies investigating this role, however, employed irreversible lesions of this nucleus. The objective of the present study was to investigate the effects of an acute and reversible inactivation of the BNST in rats submitted to the Vogel conflict test (VCT) and contextual fear conditioning, two widely employed animal models that are responsive to prototypal anxiolytic drugs. Male Wistar rats were submitted to stereotaxic surgery to bilaterally implant cannulae into the BNST. Ten minutes before the test they received bilateral microinjections of cobalt chloride (CoCl(2)) (1 mM/100 nL), a nonselective synapse blocker. CoCl(2) produced anxiolytic-like effects in tests, increasing the number of punished licks in the VCT and decreasing freezing behavior and the increase in mean arterial blood pressure and heart rate of animals re-exposed to the context where they had received electrical foot shocks 24 h before. The results indicate that the BNST is engaged in behavioral responses elicited by punished stimuli and aversively conditioned contexts, reinforcing its proposed role in anxiety.

The lateral septal area modulates the baroreflex in unanesthetized rats

The septal lateral area (LSA) is a limbic structure that is involved with autonomic and behavioral responses. In the present study we report the effect of acute and reversible LSA synaptic inhibition on the parasympathetic and the sympathetic components of baroreflex in unanesthetized rats. Neurotransmission was temporarily inhibited by bilateral microinjection of the nonselective synapse blocker CoCl(2) in the LSA. Bilateral microinjection of 100 nL of 1 mM CoCl(2) into the LSA did not affect blood pressure or heart rate baseline, suggesting no tonic LSA influence on resting cardiovascular parameters. However, 10 min after CoCl(2) microinjections, maximum tachycardiac responses to blood pressure decreases caused by intravenous infusion of sodium nitroprusside and bradycardiac responses evoked by blood pressure increases caused by intravenous infusion of phenylephrine were enhanced when compared with control values. These enhancement of both the tachycardiac and bradycardiac reflex evoked increase of baroreflex gain. Baroreflex activity returned to control values 60 min after CoCl(2) microinjections, confirming the reversible blockade. The present results indicate an involvement of the LSA in baroreflex modulation. Data suggest that synapses in the LSA play a tonic inhibitory influence on both the sympathetic and the parasympathetic components of the baroreflex in unanesthetized rats.

Both alpha1 and alpha2-adrenoceptors mediate the cardiovascular responses to noradrenaline microinjected into the bed nucleus of the stria terminal of rats

BACKGROUND AND PURPOSE

We have previously shown that noradrenaline microinjected into the bed nucleus of stria terminalis (BST) elicited pressor and bradycardiac responses in unanaesthetized rats. In the present study, we investigated the subtype of adrenoceptors that mediates the cardiovascular response to noradrenaline microinjection into the BST.

EXPERIMENTAL APPROACH

Cardiovascular responses following noradrenaline microinjection into the BST of male Wistar rats were studied before and after BST pretreatment with different doses of the selective alpha(1)-adrenoceptor antagonist WB4101, the alpha(2)-adrenoceptor antagonist RX821002, the combination of WB4101 and RX821002, the non-selective beta-adrenoceptor antagonist propranolol, the selective beta(1)-adrenoceptor antagonist CGP20712 or the selective beta(2)-adrenoceptor antagonist ICI118,551.

KEY RESULTS

Noradrenaline microinjected into the BST of unanaesthetized rats caused pressor and bradycardiac responses. Pretreatment of the BST with different doses of either WB4101 or RX821002 only partially reduced the response to noradrenaline. However, the response to noradrenaline was blocked when WB4101 and RX821002 were combined. Pretreatment with this combination also shifted the resulting dose-effect curve to the left, clearly showing a potentiating effect of this antagonist combination. Pretreatment with different doses of either propranolol or CGP20712 increased the cardiovascular responses to noradrenaline microinjected into the BST. Pretreatment with ICI118,551 did not affect cardiovascular responses to noradrenaline.

CONCLUSION AND IMPLICATIONS

The present results indicate that alpha(1) and alpha(2)-adrenoceptors mediate the cardiovascular responses to noradrenaline microinjected into the BST. In addition, they point to an inhibitory role played by the activation of local beta(1)-adrenoceptors in the cardiovascular response to noradrenaline microinjected into the BST.

Cardiovascular effects of noradrenaline microinjection in the bed nucleus of the stria terminalis of the rat brain

The bed nucleus of the stria terminalis (BST) is a limbic structure involved in regulating the hypothalamic-pituitary-adrenal axis as well as in central cardiovascular control. We report here on cardiovascular effects caused by microinjection of noradrenaline (NA) in the BST of the rat brain and the peripheral mechanisms involved in their mediation. Injection of NA (3, 7, 10, 15, 30, or 45 nmol in 100 nl) in the BST of unanesthetized rats caused long-lasting dose-related pressor and bradycardiac responses. No responses were observed when the dose of 10 nmol NA was microinjected into surrounding structures, such as the anterior commissure, the stria terminalis, the fornix, and the internal capsule, indicating a predominant action at the BST. Additionally, microinjection of 50 nmol tyramine, an indirectly acting sympathomimetic amine, caused similar pressor response, indicating local NA release in the BST. Responses to NA microinjection in the BST were markedly reduced in urethane-anesthetized rats, favoring the idea of a central action without significant leakage to the peripheral circulation. The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium and blocked by i.v. pretreatment with the selective V(1)-vasopressin antagonist dTyr(CH(2))(5)(Me)AVP, suggesting its mediation by vasopressin release into circulation. The bradycardiac response to NA microinjected into the BST was also abolished by pretreatment with the vasopressin antagonist, indicating its reflex origin. In conclusion, results indicate that microinjection of NA into the BST evokes pressor responses, which are mediated by acute vasopressin release.

Cardiovascular effects of carbachol microinjected into the bed nucleus of the stria terminalis of the rat brain

The bed nucleus of stria terminalis (BST) has been reported to be involved in central cardiovascular control in rat. We presently report on the cardiovascular effects of carbachol (CBH) microinjection into the BST as well as on local receptor and peripheral mechanisms involved in their mediation. Microinjection of CBH (0.1 to 3 nmol/100 nL) into the BST of anesthetized rats caused dose-related pressor and bradycardiac responses. The cardiovascular response evoked by 1 nmol of CBH was blocked by local microinjection of the nonselective muscarinic receptor antagonist atropine (3 nmol) or the selective M(2)-muscarinic receptor antagonist 4-DAMP (2 nmol). Microinjection of the selective M(1)-muscarinic receptor antagonist pirenzepine (6 nmol) did not affect cardiovascular responses to CBH, suggesting their mediation by local BST M(2)-muscarinic receptors. Cardiovascular responses to CBH microinjected in the BST were markedly reduced in urethane-anesthetized rats. The pressor response was potentiated by i.v. pretreatment with the ganglion blocker pentolinium (10 mg/kg) and blocked by i.v. pretreatment with the vasopressin antagonist dTyr(CH2)5(Me)AVP (50 microg/kg), suggesting involvement of circulating vasopressin in response mediation. In conclusion, results suggest that microinjection of CBH in the BST activates local M(2)-muscarinic receptor evoking pressor and bradycardiac responses, which are mediated by acute vasopressin release into circulation.