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Decreased BP (decreased + bp)
Selected AbstractsCross-sample entropy statistic as a measure of complexity and regularity of renal sympathetic nerve activity in the ratEXPERIMENTAL PHYSIOLOGY, Issue 4 2007Tao Zhang In this study, we employed both power spectral analysis and cross-sample entropy measurement to assess the relationship between two time series, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA), during a mild haemorrhage in anaesthetized Wistar rats. Removal of 1 ml of venous blood decreased BP (by 7.1 ± 0.7 mmHg) and increased RSNA (by 25.9 ± 2.4%). During these changes, the power in the RSNA signal at heart rate frequency was reduced but coherence between the spectra at heart rate frequency in RSNA and ABP remained unchanged. Cross-sample entropy was significantly increased (by 10%) by haemorrhage, revealing that there was greater asynchrony between ABP and the RSNA time series. Intrathecal administration of the glutamate receptor antagonist kynurenic acid (2 mm) almost halved (P < 0.01) the reflex increase in RSNA. Also during kynurenic acid block, haemorrhage failed to change total power, power at heart rate frequency, coherence at heart rate frequency, or the cross-sample entropy measurements. We conclude that the increase in asynchrony between ABP and RSNA during the reflex increase in RSNA was a consequence of an increase in synaptic input to the spinal renal neurones. The data show that the cross-sample entropy calculations can characterize the non-linearities of neural mechanisms underlying cardiovascular control and have a potential to reveal how some aspects of homeostatic regulation of kidney function is achieved by the autonomic nervous system. [source] Effects of Natriuretic Peptides on Intracavernous Pressure and Blood Pressure in Conscious RatsTHE JOURNAL OF SEXUAL MEDICINE, Issue 10 2008Naoki Aizawa PhD ABSTRACT Introduction., Natriuretic peptides activate particulate guanylyl cyclases and have been shown to induce penile erection in rats, rabbits, and humans. Aim., We investigated the effects of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) on intracavernous pressure (ICP) and systemic blood pressure (BP) in conscious, free-moving rats. Methods., ICP and BP were measured in male Sprague,Dawley rats after catheters were inserted into the crus corpus cavernosum and carotid artery, respectively. Natriuretic peptides were given by intravenous bolus (3, 10, and 30 nmol/kg) or continuous (0.1 and 1 nmol/kg/minute) administration. Main Outcome Measures., The number of animals with increases in ICP were determined. Amplitudes and durations of ICP responses and changes in BP were also evaluated. Results., More animals had multiple transient increases of ICP in response to ANP and BNP than to CNP. The increases in ICP were transient and appeared to be an "all or none" response. ANP and BNP decreased BP more than CNP, especially with bolus administration. Conclusions., These findings show that in rats, erectile responses can be initiated by ANP, BNP, and less effectively, by CNP. ANP and BNP have a high affinity for the natriuretic peptide receptor-A, suggesting that this receptor is involved in the responses. Aizawa N, Ishizuka O, Ogawa T, Mizusawa H, Igawa Y, Nishizawa O, and Andersson K-E. Effects of natriuretic peptides on intracavernous pressure and blood pressure in conscious rats. J Sex Med 2008;5:2312,2317. [source] Modulatory effects of static magnetic fields on blood pressure in rabbitsBIOELECTROMAGNETICS, Issue 6 2001Hideyuki Okano Abstract Acute effects of locally applied static magnetic fields (SMF) on pharmacologically altered blood pressure (BP) in a central artery of the ear lobe of a conscious rabbit were evaluated. Hypotensive and vasodilator actions were induced by a Ca2+ channel blocker, nicardipine (NIC). Hypertensive and vasoconstrictive actions were induced by a nitric oxide synthase (NOS) inhibitor, N, -nitro- L -arginine methyl ester (L-NAME). The hemodynamic changes in the artery exposed to SMF were measured continuously and analyzed by penetrating microphotoelectric plethysmography (MPPG). Concurrently, BP changes in a central artery contralateral to that of the exposed ear lobe were monitored. SMF intensity was 1,mT and the duration of exposure was 30,min. A total of 180 experimental trials were carried out in 34 healthy adult male rabbits weighing 2.6,3.8,kg. Six experimental procedures were chosen at random: (1) sham exposure without pharmacological treatment; (2) SMF exposure alone; (3) decreased BP induced by a single intravenous (iv) bolus injection of NIC (100,,M/kg) without SMF exposure; (4) decreased BP induced by injection of NIC with SMF exposure; (5) increased BP induced by a constant iv infusion of L-NAME (10,mM/kg/h) without SMF exposure; (6) increased BP induced by infusion of L-NAME with SMF exposure. The results demonstrated that SMF significantly reduced the vasodilatation with enhanced vasomotion and antagonized the reduction of BP via NIC-blocked Ca2+ channels in vascular smooth muscle cells. In addition, SMF significantly attenuated the vasoconstriction and suppressed the elevation of BP via NOS inhibition in vascular endothelial cells and/or central nervous system neurons. These results suggest that these modulatory effects of SMF on BP might, in part, involve a feedback control system for alteration in NOS activity in conjunction with modulation of Ca2+ dynamics. Bioelectromagnetics 22:408,418, 2001. © 2001 Wiley-Liss, Inc. [source] KETANSERIN-INDUCED BAROREFLEX ENHANCEMENT IN SPONTANEOUSLY HYPERTENSIVE RATS DEPENDS ON CENTRAL 5-HT2A RECEPTORSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 8 2007Fu-Ming Shen SUMMARY 1Ketanserin may influence baroreflex function by blocking 5-HT2A receptors and/or ,1 -adrenoceptors through central and/or peripheral mechanisms. 2In the present study, we tested the hypothesis that the baroreflex sensitivity (BRS)-enhancing effects of ketanserin are mediated by central 5-HT2A receptors in spontaneously hypertensive rats (SHR). 3Using a conjugate of a monoclonal antibody to the serotonin reuptake transporter (SERT) and the toxin saporin (anti-SERT-SAP), which specifically eliminates the neurons that express SERT, the effects of ketanserin (0.3 and 3.0 mg/kg, i.g.) on BRS, blood pressure (BP), heart period (HP) and blood pressure variability (BPV) were compared between conscious intact SHR and SHR pretreated with anti-SERT-SAP. 4Immunochemistry showed that, 2 weeks after intracerebroventricular injection of the toxin, 5-HT expression was strikingly attenuated in the brain, whereas values of BRS, BPV and BP were similar to those in the sham group. In intact SHR, 0.3 mg/kg ketanserin significantly improved BRS (191% control) and reduced BPV without affecting BP; at 3.0 mg/kg, ketanserin significantly increased BRS (197% control) and decreased BPV and BP. In toxin-pretreated SHR, only the high dose of ketanserin improved BRS (132% control), neither of the ketanserin doses reduced BPV, but both significantly decreased BP. 5We conclude that the BRS-enhancing effects of ketanserin are mediated largely by central 5-HT2A receptors, whereas the antihypertensive effect of ketanserin persists even after destruction of serotonergic neurons in the central nervous system. [source] Acute And Chronic Sympathoinhibition On Carotid Artery Diameter Of Spontaneously Hypertensive Rats: Effects Of Clonidine And FlesinoxanCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 9 2000H Dabiré SUMMARY 1. Hypertensive conduit arteries are thicker and stiffer than those of normotensive controls. Whether they are specifically sensitive to central sympathoinhibition has never been investigated. 2. The effects of acute (24 h infusion) and chronic (4 week infusion) treatments with clonidine (0.01 and 0.1 mg/kg per day) and flesinoxan (1 and 3 mg/kg per day) on carotid artery diameter were investigated in spontaneously hypertensive rats. At the end of treatment, blood pressure (BP) was recorded in the rats while they were conscious. Rats were then anaesthetized for carotid artery diameter measurements using an ultrasonic echo-tracking device. 3. In conscious rats, clonidine significantly decreased BP and heart rate (HR) following acute but not chronic treatment. In contrast, flesinoxan significantly decreased BP following both the acute and chronic treatment. In anaesthetized animals, the two agents have opposite effects on isobaric carotid artery diameter, with a decrease under clonidine and an increase under flesinoxan. After 4 weeks infusion, the reactivity of aortic rings was studied in organ chambers. Flesinoxan, but not clonidine, caused the relaxation of potassium chloride precontracted aortic segments. 4. The results indicate that although clonidine and flesinoxan are centrally acting antihypertensive agents, the drug-induced changes in isobaric carotid diameter may be influenced by local factors independent of the central action of the two drugs. [source] | |||||||||||||