Blood Pressure In Conscious Rats Research Articles

In vivo effect of withacoagulin and coagulin C isolated from Withania coagulans Dunal fruits on blood pressure of albino rats

The present study was designed to evaluate the in vivo effect of withacoagulin and coagulin C isolated from Withania coagulans Dunal fruits on blood pressure of albino rats. Hypertension in rats was experimentally induced by giving DOCA (10mg/kg; i.p.) along with diet high in sodium chloride salt. Withacoagulin and coagulin C were isolated from Withania coagulans Dunal fruits. Comparative effect of withacoagulin and coagulin C was observed against standard verapamil, a known antihypertensive drug. Female Albino rats (100-120 g) were divided into seven experimental groups (n=6). Normal control, Verapamil standard control (50 mg/kg, p.o.), withacoagulin treatment groups (25, 50 mg/kg; p.o.), coagulin C treatment groups (25, 50 mg/kg; p.o.) and Toxic control (DOCA with 2% normal saline ad libitum). The hypertensive rats (>150mm Hg) were choosen for the treatment. Noninvasive tail blood pressure amplifier (NIBP200A) was used to measure blood pressure of conscious rats at a fixed interval of time every day for four weeks. A significant decrease (P< 0.05) in the blood pressure of withacoagulin treated and standard group were observed. Withacoagulin at dose 25 mg/kg produced significant (P< 0.05) antihypertensive effect. Withacoagulin at 50 mg/kg dose produced highly significant antihypertensive effect (P< 0.001) as compared to standard calcium channel blocker, verapamil. Coagulin C has been found to have no significant antihypertensive effect on albino rats.

Albumin Coating Prevents Cardiac Effect of the Magnetic Nanoparticles.

We have showed that surface layer can determine cardiac effects of the magnetic nanoparticles (MNPs). Considering the high binding capacity of albumin and low side-effects, the aim of this study was to evaluate the influence of albumin coating on the cardiovascular effects of two manganese ferrite-based MNPs: citrate-coated and bare MNPs. Isolated rat hearts were perfused with citrate-coated magnetic nanoparticles (CiMNPs), citrate albumin-coated magnetic nanoparticles (CiAlbMNPs), bare magnetic nanoparticles (BaMNPs), and albumin-coated magnetic nanoparticles (AlbMNPs). CiMNPs induce a transient decrease in the left ventricular end-systolic pressure, +dP/dt and -dP/dt. These effects were not worsened by albumin coating. BaMNPs significantly increased the left ventricular end-diastolic pressure and perfusion pressure and decreased the +dP/dt and -dP/dt. These effects were completely absent in hearts perfused with AlbMNPs. None of the MNPs changed heart rate or arterial blood pressure in conscious rats. Magnetic signals in isolated hearts perfused with BaMNPs were significantly higher than AlbMNPs perfused hearts. However, the magnetic signal in heart tissue was similar when the MNPs were infused in conscious rats. These data indicate that albumin-coated can reduce cardiovascular effects of MNPs. These findings suggest a protective effect of albumin surface in MNPs, favoring its future therapeutic applications.

Blood Pressure Regulation by the Rostral Ventrolateral Medulla in Conscious Rats: Effects of Hypoxia, Hypercapnia, Baroreceptor Denervation, and Anesthesia.

Current understanding of the contribution of C1 neurons to blood pressure (BP) regulation derives predominantly from experiments performed in anesthetized animals or reduced ex vivo preparations. Here, we use ArchaerhodopsinT3.0 (ArchT) loss-of-function optogenetics to explore BP regulation by C1 neurons in intact, unanesthetized rats. Using a lentivirus that expresses ArchT under the Phox2b-activated promoter PRSx8 (PRSx8-ArchT), ∼65% of transduced neurons were C1 (balance retrotrapezoid nucleus, RTN). Other rats received CaMKII-ArchT3.0 AAV2 (CaMKII-ArchT), which transduced C1 neurons and larger numbers of unidentified glutamatergic and GABAergic cells. Under anesthesia, ArchT photoactivation reduced sympathetic nerve activity and BP and silenced/strongly inhibited most (7/12) putative C1 neurons. In unanesthetized PRSx8-ArchT-treated rats breathing room air, bilateral ArchT photoactivation caused a very small BP reduction that was only slightly larger under hypercapnia (6% FiCO2), but was greatly enhanced during hypoxia (10 and 12% FiO2), after sino-aortic denervation, or during isoflurane anesthesia. The degree of hypotension correlated with percentage of ArchT-transduced C1 neurons. ArchT photoactivation produced similar BP changes in CaMKII-ArchT-treated rats. Photoactivation in PRSX8-ArchT rats reduced breathing frequency (FR), whereas FR increased in CaMKII-ArchT rats. We conclude that the BP drop elicited by ArchT activation resulted from C1 neuron inhibition and was unrelated to breathing changes. C1 neurons have low activity under normoxia, but their activation is important to BP stability during hypoxia or anesthesia and contributes greatly to the hypertension caused by baroreceptor deafferentation. Finally, C1 neurons are marginally activated by hypercapnia and the large breathing stimulation caused by this stimulus has very little impact on resting BP.SIGNIFICANCE STATEMENT C1 neurons are glutamatergic/peptidergic/catecholaminergic neurons located in the medulla oblongata, which may operate as a switchboard for differential, behavior-appropriate activation of selected sympathetic efferents. Based largely on experimentation in anesthetized or reduced preparations, a rostrally located subset of C1 neurons may contribute to both BP stabilization and dysregulation (hypertension). Here, we used Archaerhodopsin-based loss-of-function optogenetics to explore the contribution of these neurons to BP in conscious rats. The results suggest that C1 neurons contribute little to resting BP under normoxia or hypercapnia, C1 neuron discharge is restrained continuously by arterial baroreceptors, and C1 neuron activation is critical to stabilize BP under hypoxia or anesthesia. This optogenetic approach could also be useful to explore the role of C1 neurons during specific behaviors or in hypertensive models.

The Effect of Chronic Activation of the Novel Endocannabinoid Receptor GPR18 on Myocardial Function and Blood Pressure in Conscious Rats.

Although acute activation of the novel endocannabinoid receptor GPR18 causes hypotension, there are no reports on GPR18 expression in the heart or its chronic modulation of cardiovascular function. In this study, after demonstrating GPR18 expression in the heart, we show that chronic (2 weeks) GPR18 activation with its agonist abnormal cannabidiol (abn-cbd; 100 µg·kg·d; i.p) produced hypotension, suppressed the cardiac sympathetic dominance, and improved left ventricular (LV) function (increased the contractility index dp/dtmax and reduced LV end-diastolic pressure, LVEDP) in conscious rats. Ex vivo studies revealed increased: (1) cardiac and plasma adiponectin (ADN) levels; (2) vascular (aortic) endothelial nitric oxide synthase (eNOS) expression, (3) vascular and serum nitric oxide (NO) levels; (4) myocardial and plasma cyclic guanosine monophosphate (cGMP) levels; (5) phosphorylation of myocardial protein kinase B (Akt) and extracellular signal regulated kinase 1/2 (ERK1/2) along with reduced myocardial reactive oxygen species (ROS) in abn-cbd treated rats. These biochemical responses contributed to the hemodynamic responses and were GPR18-mediated because concurrent treatment with the competitive GPR18 antagonist (O-1918) abrogated the abn-cbd-evoked hemodynamic and biochemical responses. The current findings present new evidence for a salutary cardiovascular role for GPR18, mediated, at least partly, via elevation in the levels of adiponectin.

Butylidenephthalide antagonizes cromakalim-induced systolic pressure reduction in conscious normotensive rats.

BackgroundButylidenephthalide (Bdph), a main constituent of Ligusticum chuanxiong Hort., was reported to have selective antianginal effect without changing blood pressure in conscious rat. Recently, we have observed that Bdph antagonized cromakalim, an ATP-dependent K+ channel opener, in guinea-pig trachea. Thus, we were interested in investigating whether Bdph at the dose without changing blood pressure antagonized cromakalim-induced systolic pressure reduction in conscious rats.MethodsSystolic arterial pressures of conscious rats were determined by using the indirect tail-cuff method.ResultsBdph (30 mg/kg, i.p.) did not affect baseline systolic pressure in conscious normotensive and spontaneous hypertensive rats. Bdph (30 mg/kg, i.p.) also did not affect log dose–response curves of prazosin, clonidine and Bay K 8644, a Ca2+ channel activator, in normotensive rats. However, Bdph (30 mg/kg, i.p.) similar to 4-aminopyridine (4-AP, 0.4 mg/kg, i.p.), a K+ channel blocker, non-parallelly but surmountably, and partially similar to glibenclamide (GBC, 10 mg/kg, i.v.), an ATP-sensitive K+ channel blocker, surmountably but not parallelly rightward shifted the log dose-systolic pressure reduction curve of cromakalim, an ATP-sensitive K+ channel opener, in normotensive rats, respectively.DiscussionThe antagonistic effect of Bdph against cromakalim was similar to that of 4-AP, a K+ channel blocker of Kv1 family, and partially similar to that of GBC, an ATP-sensitive K+ channel blocker. Thus, Bdph may be a kind of K+ channel blockers, which have been reviewed to have a potential clinical use for Alzheimer disease. Indeed, Bdph has also been reported to reverse the deficits of inhibitory avoidance performance and improve memory in rats. Recently, 4-AP was reported to treat Episodic ataxia type 2 (EA2) which is a form of hereditary neurological disorder. Consistently, Bdph was recently reported to have antihyperglycemic activity in mice, since GBC is a powerful oral hypoglycemic drug.ConclusionsBdph similar to 4-AP and partially similar to GBC may block Kv1 family and ATP-sensitive K+ channels in conscious normotensive rats.

Possible role of afferent autonomic signals in abdominal organs in anorexic and cardiovascular responses to nicotine injection in rats

Smoking generally causes an increase in nicotine levels in the blood, affecting the brain components, such as the hypothalamus (feeding-related area) or the brain stem (cardiovascular control area). In terms of nicotine transmission to the brain, a new insight that the afferent vagal nerve in the liver is important for sensing increased nicotine levels in the blood and informing the brain was reported in an experiment with rats. However, it has not been clarified whether the afferent autonomic nerve system is implicated in feeding and cardiovascular responses to nicotine. Here, we examined the possible role of afferent autonomic nerve transmission in rats in regulating feeding behavior and cardiovascular functions by nicotine. An intravenous injection of nicotine dose dependently increased the blood pressure (BP) in urethane-anesthetized rats; high nicotine doses also led to an increase in BP in conscious rats. Further, an intravenous injection of nicotine for 3 days reduced food intake and body weight gain in rats. The weight-reducing action of intravenous nicotine was abolished by blocking the afferent sympathetic signals in the abdominal organs, but not the vagal nerve signals. Moreover, the hypertensive action of nicotine was not abolished either by afferent sympathectomy or by vagotomy. Thus, these data suggest that nicotine injected into the vein acts on the afferent sympathetic nerve in the abdominal organs and transmits signals to the brain for reducing body weight, but not for suppressing appetite or increasing BP.

Neuronal nitric oxide synthase-dependent elevation in adiponectin in the rostral ventrolateral medulla underlies g protein-coupled receptor 18-mediated hypotension in conscious rats.

Direct activation of the endocannabinoid receptor G protein-coupled receptor 18 (GPR18) in the rostral ventrolateral medulla (RVLM) of conscious rats by abnormal cannabidiol (Abn CBD; trans-4-[3-methyl-6-(1-methylethenyl)-2-cyclohexen-1-yl]-5-pentyl-1,3-benzenediol) elevates local nitric oxide (NO) and adiponectin (ADN) levels and reduces oxidative stress and blood pressure (BP). However, the molecular mechanisms for GPR18-mediated neurochemical responses, including the nitric oxide synthase isoform that generates NO, and their potential causal link to the BP reduction are not known. We hypothesized that GPR18-mediated enhancement of Akt, extracellular signal-regulated kinase 1/2 (ERK1/2), and neuronal nitric oxide synthase (nNOS) phosphorylation, triggered by a reduction in cAMP, accounts for the NO/ADN-dependent reductions in RVLM oxidative stress and BP. Intra-RVLM GPR18 activation (Abn CBD; 0.4 μg) enhanced RVLM Akt, ERK1/2, and nNOS phosphorylation as well as ADN levels during the hypotensive response. Prior GPR18 blockade with O-1918 (1,3-dimethoxy-5-methyl-2-[(1R,6R)-3-methyl-6-(1-methylethenyl)-2-cyclohexen-1-yl]benzene) produced the opposite effects and abrogated Abn CBD-evoked neurochemical and BP responses. Pharmacological inhibition of RVLM phosphoinositide 3-kinase (PI3K)/Akt (wortmannin), ERK1/2 (PD98059 [2-​(2-​amino-​3-​methoxyphenyl)-​4H-​1-​benzopyran-​4-​one]), or nNOS (N(ω)-propyl-l-arginine), or activation of adenylyl cyclase (forskolin) virtually abolished intra-RVLM Abn CBD-evoked hypotension and the increases in Akt, ERK1/2, and nNOS phosphorylation and in ADN levels in the RVLM. Our pharmacological and neurochemical findings support a pivotal role for PI3K, Akt, ERK1/2, nNOS, and adenylyl cyclase, via modulation of NO, ADN, and cAMP levels, in GPR18 regulation of the RVLM redox state and BP in conscious rats.

Manganese ferrite-based nanoparticles induce ex vivo, but not in vivo, cardiovascular effects

Magnetic nanoparticles (MNPs) have been used for various biomedical applications. Importantly, manganese ferrite-based nanoparticles have useful magnetic resonance imaging characteristics and potential for hyperthermia treatment, but their effects in the cardiovascular system are poorly reported. Thus, the objectives of this study were to determine the cardiovascular effects of three different types of manganese ferrite-based magnetic nanoparticles: citrate-coated (CiMNPs); tripolyphosphate-coated (PhMNPs); and bare magnetic nanoparticles (BaMNPs). The samples were characterized by vibrating sample magnetometer, X-ray diffraction, dynamic light scattering, and transmission electron microscopy. The direct effects of the MNPs on cardiac contractility were evaluated in isolated perfused rat hearts. The CiMNPs, but not PhMNPs and BaMNPs, induced a transient decrease in the left ventricular end-systolic pressure. The PhMNPs and BaMNPs, but not CiMNPs, induced an increase in left ventricular end-diastolic pressure, which resulted in a decrease in a left ventricular end developed pressure. Indeed, PhMNPs and BaMNPs also caused a decrease in the maximal rate of left ventricular pressure rise (+dP/dt) and maximal rate of left ventricular pressure decline (−dP/dt). The three MNPs studied induced an increase in the perfusion pressure of isolated hearts. BaMNPs, but not PhMNPs or CiMNPs, induced a slight vasorelaxant effect in the isolated aortic rings. None of the MNPs were able to change heart rate or arterial blood pressure in conscious rats. In summary, although the MNPs were able to induce effects ex vivo, no significant changes were observed in vivo. Thus, given the proper dosages, these MNPs should be considered for possible therapeutic applications.

Activation of central nicotinic acid receptor GPR109A increases blood pressure in conscious rats (841.11)

The hypolipidemic drug nicotinic acid (NA) elicits prostaglandins (PGs)‐dependent flushing reaction via GPR109A activation. There are no reports on GPR109A expression or function in the rostral ventrolateral medulla (RVLM), despite evidence that NA reaches the brain. We present the first evidence for GPR109A expression in the RVLM (Western blot). Next, we showed in conscious rats that intra‐RVLM NA (estimated doses to reach the RVLM following systemic administration) increased BP and reduced HR, which resembled responses elicited by intra‐RVLM L‐glutamate. The pressor effect of NA was abolished by selective NMDAR blockade (2‐amino‐5‐phosphonopentanoic acid; AP5) and enhanced by L‐glutamate uptake inhibition (L‐trans‐Pyrrolidine‐2,4‐dicarboxylic acid; PDC). Further NA elevated L‐glutamate level in culture medium of PC12 cells, which exhibit neuronal phenotype and express GPR109A. These novel findings suggest that L‐glutamate release is involved in RVLM GPR109A‐mediated brief pressor response. Ongoing integrative and molecular studies will elucidate the role of PGs and oxidative stress in the delayed pressor response caused by intra‐RVLM NA. The findings are clinically relevant because they elucidate the mechanisms of a centrally mediated deleterious effect of NA on BP, and yield new insight into the potential use of concurrent therapeutics to circumvent such deleterious effect.

Opiorphin increases blood pressure of conscious rats through renin-angiotensin system (RAS)

Human opiorphin is a recently identified endogenous pentapeptide, encoded by ProL1 multigenes family that contributes to cardiovascular modulation. The aim of this study was to evaluate the effect of opiorphin through intravenous injection (i.v.) on mean arterial pressure (MAP) regulation. To investigate the bioactivity of opiorphin, a rat cannulation model was developed for MAP measurement and blood sampling. In our present study, opiorphin (200–700nmol/kg) increased MAP in dose-related and time-dependent manner in conscious rats, which associated highly with the elevation of angiotensin II (AngII) levels in serum. Furthermore, the MAP elevation induced by opiorphin was completely blocked by AngII receptor antagonist valsartan and partially attenuated by angiotensin-converting enzyme inhibitor captopril. Finally, we tested the effect of opiorphin in hypoxia condition, which exhibited that opiorphin reversed hypoxia induced hypotension in conscious rats. Taken together, these results indicated that opiorphin may play an important role in the modulation of blood pressure through AngII dependent pathway, which may help future development of potent clinical therapeutics for emergency treatment.

Nesfatin‐1 activates cardiac vagal neurons of nucleus ambiguus and elicits bradycardia in conscious rats

Nesfatin-1, a peptide whose receptor is yet to be identified, has been involved in the modulation of feeding, stress, and metabolic responses. More recently, increasing evidence supports a modulatory role for nesfatin-1 in autonomic and cardiovascular activity. This study was undertaken to test if the expression of nesfatin-1 in the nucleus ambiguus, a key site for parasympathetic cardiac control, may be correlated with a functional role. As we have previously demonstrated that nesfatin-1 elicits Ca²⁺ signaling in hypothalamic neurons, we first assessed the effect of this peptide on cytosolic Ca²⁺ in cardiac pre-ganglionic neurons of nucleus ambiguus. We provide evidence that nesfatin-1 increases cytosolic Ca²⁺ concentration via a Gi/o-coupled mechanism. The nesfatin-1-induced Ca²⁺ rise is critically dependent on Ca²⁺ influx via P/Q-type voltage-activated Ca²⁺ channels. Repeated administration of nesfatin-1 leads to tachyphylaxis. Furthermore, nesfatin-1 produces a dose-dependent depolarization of cardiac vagal neurons via a Gi/o-coupled mechanism. In vivo studies, using telemetric and tail-cuff monitoring of heart rate and blood pressure, indicate that microinjection of nesfatin-1 into the nucleus ambiguus produces bradycardia not accompanied by a change in blood pressure in conscious rats. Taken together, our results identify for the first time that nesfatin-1 decreases heart rate by activating cardiac vagal neurons of nucleus ambiguus. Our results indicate that nesfatin-1, one of the most potent feeding peptides, increases cytosolic Ca²⁺ by promoting Ca²⁺ influx via P/Q channels and depolarizes nucleus ambiguus neurons; both effects are Gi/o-mediated. In vivo studies indicate that microinjection of nesfatin-1 into nucleus ambiguus produces bradycardia in conscious rats. This is the first report that nesfatin-1 increases the parasympathetic cardiac tone.

Pharmacological Characterization of BR-A-657, a Highly Potent Nonpeptide Angiotensin II Receptor Antagonist

The pharmacological profile of BR-A-657, 2-n-butyl-5-dimethylamino-thiocarbonyl-methyl-6-methyl-3-{[2-(1H-tetrazole-5-yl)biphenyl-4-yl]methyl}-pyrimidin-4(3H)-one, a new nonpeptide AT1-selective angiotensin receptor antagonist, has been investigated in a variety of in vitro and in vivo experimental models. In the present study, BR-A-657 displaced [(125)I][Sar(1)-Ile(8)]angiotensin II (Ang II) from its specific binding sites to AT1 subtype receptors in membrane fractions of HEK-293 cells with an IC50 of 0.16 nM. In a functional assay using isolated rabbit thoracic aorta, BR-A-657 inhibited the contractile response to Ang II (pD'2: 9.15) with a significant reduction in the maximum. In conscious rats, BR-A-657 (0.01, 0.1, 1 mg/kg; intravenously (i.v.)) dose-dependently antagonized Ang II-induced pressor responses. In addition, BR-A-657 dose-dependently decreased mean arterial pressure in furosemide-treated rats and renal hypertensive rats. Moreover, BR-A-657 given orally at 1 and 3 mg/kg reduced blood pressure in conscious renal hypertensive rats. Taken together, these findings indicate that BR-A-657 is a potent and specific antagonist of Ang II at the AT1 receptor subtype, and reveal the molecular basis responsible for the marked lowering of blood pressure in conscious rats.

Uridine adenosine tetraphosphate affects contractility of mouse aorta and decreases blood pressure in conscious rats and mice

in the anaesthetized rat, uridine adenosine tetraphosphate (Up(4) A) is a circulating, endothelium-derived vasoconstrictor presumably operating as such in un-anaesthetized animals. The present study investigated the in vivo effects of Up(4) A in conscious mice and rats, and its direct vascular effects in the mouse aorta in vitro. in vivo, Up(4) A was given as step-up infusion at rates of 8-512 nmol min(-1) kg(-1) for 30 min periods in chronically catheterized rodents. In vitro, the effect of Up(4) A on rings of mouse aortae mounted in a myograph was tested. high doses of Up(4) A (mice: 512 nmol min(-1) kg(-1) ; rats: 128 nmol min(-1) kg(-1) ) caused hypotension (99 (+/-)4 to 64 7(+/-) mmHg and 114 (+/-) 3 to 108 (+/-) 3 mmHg, respectively, both P < 0.01). In rats, Up(4) A significantly decreased sodium excretion by >75% and potassium excretion by approximately 60% without significant changes in urine flow. Exposure of phenylephrine-contracted rings to increasing concentrations of Up(4) A elicited contraction at 10(-7) and 10(-6) molL(-1) (18 ± 2% and 76 (+/-) 16% respectively); unexpectedly, 10(-5) molL(-1) caused a biphasic response with a contraction (19 6(+/-)2%) followed by a relaxation (-46 (+/-) 6%). No relaxation was observed when the concentration was increased further. Bolus exposure to 10(-5) molL(-1) of Up(4) A caused contraction (+80 (+/-) 2%). Added successively to untreated vessels, increasing concentrations of Up(4) A (10(-7) -10(-5) molL(-1) ) induced a biphasic response of contraction followed by relaxation. up(4) A has direct biphasic effects on vascular smooth muscle of the mouse aorta but vasoconstriction dominates at low concentrations. In conscious rodents, step-up infusions of Up(4) A elicit hypotension and electrolyte retention.

Cardioprotective Actions of Ascorbic Acid during Isoproterenol-Induced Acute Myocardial Infarction in Rats

Background/Aims: In the present study, we tested whether or not acute antioxidant treatment with vitamin C is able to protect the heart during myocardial infarction. The effects of vitamin C on the autonomic balancing of the heart and on the histopathological and immunohistochemical changes in response to isoproterenol administration (ISO) were evaluated. Methods: Four groups of male Wistar rats (n = 32) were studied: control; ISO treated; vitamin C treated; ISO + vitamin C treated. ISO 150 mg/kg was administered for 2 consecutive days. Vitamin C (250 mg/kg, oral) was administered 30 min before each ISO treatment. Phenylephrine and sodium nitroprusside were administrated to increase or decrease blood pressure in conscious rats. Results: The baroreceptor reflex index for bradycardia was significantly reduced in the ISO group (control, –3.4 ± 0.3 beats/mm Hg; ISO –2 ± 0.4 beats/mm Hg) and vitamin C treatment significantly improved the reflex index (–2.9 ± 0.7 beats/mm Hg). Treatment with vitamin C showed mild degenerative changes in the myocardial tissue of the ISO group. The antioxidant was able to decrease the inducible nitric oxide (iNOS) expression in rats treated with vitamin C. Conclusion: Vitamin C administration proved to be effective in reducing the extent of myocardial damage during ISO-induced myocardial infarction in rats associated with an iNOS downregulation and improving the autonomic balancing of the heart.

Effect of the Multitargeted Receptor Tyrosine Kinase Inhibitor, ABT-869 [N-(4-(3-Amino-1H-indazol-4-yl)phenyl)-N′-(2-fluoro-5-methylphenyl)urea], on Blood Pressure in Conscious Rats and Mice: Reversal with Antihypertensive Agents and Effect on Tumor Growth Inhibition

ABT-869 [N-(4-(3-amino-1H-indazol-4-yl)phenyl)-N'-(2-fluoro-5-methylphenyl)urea] is a novel multitargeted inhibitor of the vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) receptor tyrosine kinase family members. ABT-869 demonstrates tumor growth inhibition in multiple preclinical animal models and in early clinical trials. VEGF receptor inhibition is also associated with reversible hypertension that may limit its benefit clinically. To evaluate optimal therapeutic approaches to prevent hypertension with VEGF receptor inhibition, we characterized the dose-dependent effects of seven antihypertensive agents from three mechanistic classes [angiotensin-converting enzyme inhibitors (ACEis), angiotensin receptor blockers (ARBs), calcium channel blockers (CCBs)] on hypertension induced by ABT-869 in conscious telemetry rats. We report that ABT-869-induced hypertension can be prevented and reversed with subtherapeutic or therapeutic doses of antihypertensive drugs with a general rank order of ACEi > ARB > CCB. In SCID mice, the ACE inhibitor, enalapril (C(20)H(28)N(2)O(5) x C(4)H(4)O(4)) at 30 mg/kg, prevented hypertension, with no attenuation of the antitumor efficacy of ABT-869. These studies demonstrate that the adverse cardiovascular effects of the VEGF/PDGF receptor tyrosine kinase inhibitor, ABT-869, are readily controlled by conventional antihypertensive therapy without affecting antitumor efficacy.

CGRP function‐blocking antibodies inhibit neurogenic vasodilatation without affecting heart rate or arterial blood pressure in the rat

Calcitonin gene-related peptide (CGRP) receptor antagonists effectively abort migraine headache and inhibit neurogenic vasodilatation in humans as well as rat models. Monoclonal antibodies typically have long half-lives, and we investigated whether or not function-blocking CGRP antibodies would inhibit neurogenic vasodilatation with a long duration of action and therefore be a possible approach to preventive therapy of migraine. During chronic treatment with anti-CGRP antibodies, we measured cardiovascular function, which might be a safety concern of CGRP inhibition. We used two rat blood flow models that measure electrically stimulated vasodilatation in the skin or in the middle meningeal artery (MMA). These vasomotor responses are largely dependent on the neurogenic release of CGRP from sensory afferents. To assess cardiovascular function during chronic systemic anti-CGRP antibody treatment, we measured heart rate and blood pressure in conscious rats. Treatment with anti-CGRP antibodies inhibited skin vasodilatation or the increase in MMA diameter to a similar magnitude as treatment with CGRP receptor antagonists. Although CGRP antibody treatment had a slower onset of action than the CGRP receptor antagonists, the inhibition was still evident 1 week after dosing. Chronic treatment with anti-CGRP antibodies had no detectable effects on heart rate or blood pressure. We showed for the first time that anti-CGRP antibodies exert a long lasting inhibition of neurogenic vasodilatation in two different rat models of arterial blood flow. We have provided strong preclinical evidence that anti-CGRP antibody may be a suitable drug candidate for the preventive treatment of migraine.

Role of α1‐adrenergic receptors in detrusor overactivity induced by cold stress in conscious rats

alpha(1)-Adrenergic receptors (ARs) are involved in micturition control both centrally and peripherally. alpha(1)-AR antagonists improve not only voiding but also storage symptoms in patients with bladder outlet obstruction. We investigated the role of alpha(1)-AR mechanisms involved in detrusor overactivity induced by cold stress in conscious rats. Continuous cystometry was performed at room temperature (RT, 28 +/- 2 degrees C) and for 40 min at cold temperature (CT, 4 +/- 2 degrees C). Voiding interval (VI), micturition volume (MV), and bladder capacity (BC) were evaluated before and after intravenous administration of KMD-3213 (selective alpha(1A)-AR antagonist), naftopidil (selective alpha(1D)-AR antagonist), tamsulosin (selective alpha(1A/1D)-AR antagonist), and prazosin (non-selective alpha(1)-AR antagonist). Blood pressure (BP), cumulative voided volume and body temperature were also evaluated. At RT, none of the AR antagonists caused significant change in the cystometric parameters. During 40 min of cold stress cumulative voided volume and body temperature did not change, but there were significant decreases in VI, MV, and BC. Low doses of the AR antagonists had no effect on CT-induced decreases of these variables. However, high doses of KMD-3213, tamsulosin, naftopidil and prazosin significantly inhibited the CT-induced decreases in VI, MV, and BC. CT caused a significant increase in BP, and this was not affected by low doses of the AR antagonists. However, high doses of prazosin significantly lowered the CT-induced increase of BP. Cold stress induces detrusor overactivity and increases BP in conscious rats. These effects are mediated, at least in part, by alpha(1A)-AR and alpha(1D)-AR subtypes and can be prevented/reduced by alpha(1)-AR antagonists.

Effects of Angiotensin Type 2 Receptor Overexpression in the Rostral Ventrolateral Medulla on Blood Pressure and Urine Excretion in Normal Rats

Central angiotensin II plays a critical role in the regulation of cardiovascular function and autonomic activity, in part, via angiotensin type 1 receptors in the rostral ventrolateral medulla (RVLM). Increasing evidence indicates that angiotensin II can also act on angiotensin type 2 receptors (AT(2)Rs) to exert antagonistic effects. In the current study we determined the effects of overexpression of AT(2)R in the RVLM on sodium and water excretion and on blood pressure in conscious rats. The overexpression of AT(2)R was induced by bilateral microinjection of the AT(2)R adenovirus (Ad5-SYN-AT2R-IRES-EGFP, 2.5 x 10(6) infection units in 0.5 microL; Ad5-SYN-EGFP as the control, 2.5 x 10(6) infection units in 0.5 microL) into the RVLM of rats. Immunofluorescence staining showed that microinjection of AT(2)R adenovirus into the RVLM evoked local overexpression. Significant overexpression of AT(2)R in the RVLM began at 24 hours and was sustained up to 12 days after microinjection. Overexpression of AT(2)R in the RVLM significantly decreased the nocturnal arterial blood pressure and increased the 24-hour urine excretion at days 2, 3, and 4 after gene delivery compared with the control rats. These alterations were abolished by the microinfusion of captopril into the RVLM and were enhanced by angiotensin II infusion. Overexpression of AT(2)R in the RVLM also significantly decreased the urine concentration of noradrenaline and 24-hour noradrenaline excretion (1.1+/-0.5 microg in control rats and 2.4+/-0.5 microg in AT(2)R rats; P<0.05). These results suggest that overexpression of AT(2)R in the RVLM induced a diuresis that may be mediated, in part, by sympathoinhibition.

795: Role of Serotonergic Receptors on Intracavernous Pressure and Blood Pressure in Conscious Rats

795: Role of Serotonergic Receptors on Intracavernous Pressure and Blood Pressure in Conscious Rats

Vascular Endothelial Growth Factor Signaling to Endothelial Nitric Oxide Synthase

See related article, pages 715–722 There is substantial evidence supporting the idea that the process of angiogenesis requires the synthesis of endothelium-derived nitric oxide (NO). NO, characterized as a major endothelial-derived relaxing factor, exerts paracrine and autocrine roles in maintaining cardiovascular homeostasis, vascular tone, and microvascular permeability. During the early steps of angiogenesis in which new blood vessels sprout from existing vascular beds, there is a persistence of vasodilation and increase in vascular permeability, suggesting that these hemodynamic changes in the existing vasculature are indispensable during an angiogenic process. A number of angiogenic factors can triggers the release of NO, synthesized by the endothelial isoform of NO synthase (eNOS). One such factor is the vascular endothelial growth factor (VEGF), which as its name implies, is a critical mitogenic, chemoattractant, and survival factor for endothelial cells1 in addition to being characterized as a potent vascular permeability factor.2 Early studies have demonstrated that VEGF can readily stimulate NO production in cultured cells and isolated blood vessels and that NO is essential in mediating the VEGF-induced endothelial cell proliferation and organization into tubes in 3D cultures.3,4 Subsequent in vivo studies have also demonstrated that eNOS knockout mice had significantly attenuated VEGF and ischemia induced angiogenesis and vascular permeability.5,6 These studies place eNOS derived NO as a key mediator of VEGF induced angiogenesis in postnatal mice. Since the discovery of VEGF, or VEGF-A, and subsequent members of the VEGF family (VEGF-B, -C, -D, -E, and placenta growth factor, PlGF), intense research has been performed to elucidate their modes of action. These growth factor ligands bind to 3 receptor tyrosine kinases (RTKs), namely VEGF receptor-1, -2, and -3 as well as to coreceptors such as heparan sulfate proteoglycans or neuropilins. Like many other RTKs, these receptors are able to form …