Neutrophil/lymphocyte ratio elevation in renal dysfunction is caused by distortion of leukocyte hematopoiesis in bone marrow.

OBJECTIVE: We investigate the mechanism of neutrophil/lymphocyte ratio (NLR) elevation, a useful prognostic marker in patients with cardiovascular diseases (CVDs). METHODS: In this clinical study, we retrospectively searched for factors associated with NLR elevation in cardiovascular outpatients. In animal experiments using mice with adenine-induced nephropathy, we further examined the hematopoietic process in bone marrow and explored the mechanism of NLR elevation. RESULT: In patients with CVDs or their risk factors, multiple regression analysis revealed that decrease in estimated glemerular filtration rate and increase in white blood cell count were significantly associated with increase in NLR. In mice with adenine-induced nephropathy, NLR and serum indoxyl sulfate (IS) levels were increased. Fluorescence-activated cell sorting revealed the increase in the number of myeloid progenitors and decrease in the number of common lymphoid progenitors, suggesting biased granulocyte side in the hematopoietic process in bone marrow. Treatment with oral charcoal adsorbent AST-120 decreased serum concentration of IS and normalized NLR and bone marrow abnormalities in mice with adenine-induced nephropathy. CONCLUSION: Renal function was a strong determinant of NLR in cardiovascular outpatients. NLR elevation due to renal impairment is caused by distortion of the hematopoietic process in bone marrow. IS plays a significant role in these processes.

Mechanisms underlying the renoprotective effect of GABA against ischaemia/reperfusion-induced renal injury in rats.

Excitation of the renal sympathetic nervous system is important for the development of ischaemic acute kidney injury (AKI) in rats. We reported that intravenous treatment with GABA has preventive effects against ischaemia/reperfusion (I/R)-induced renal dysfunction with histological damage in rats; however, the mechanisms underlying these effects on renal injury remain unknown. Thus, the aim of the present study was to clarify how GABA mechanistically affects ischaemic AKI in rats. Ischaemic AKI was induced in rats by clamping the left renal artery and vein for 45 min and then reperfusing the kidney to produce I/R-induced injury. Treatment with the GABAB receptor antagonist CGP52432 (100 nmol/kg, i.v., or 1 nmol/kg, i.c.v.) abolished the suppressive effects of 50 µmol/kg, i.v., GABA on enhanced renal sympathetic nerve activity (RSNA) during ischaemia, leading to elimination of the renoprotective effects of GABA. Intracerebroventricular treatment with 0.5 µmol/kg GABA or i.v. treatment with 1 µmol/kg baclofen, a selective GABAB receptor agonist, prevented the I/R-induced renal injury equivalent to i.v. treatment with GABA. Conversely, i.v. treatment with 10 µmol/kg bicuculline, a GABAA receptor antagonist, failed to affect the preventive effects of GABA against ischaemic AKI. We therefore concluded that GABAB receptor stimulation in the central nervous system, rather than peripheral GABAB receptor stimulation, mediates the preventive effect of GABA against ischaemic AKI by suppressing the enhanced RSNA induced by renal ischaemia.

Involvement of renal sympathetic nerve overactivation in the progression of chronic kidney disease in rats.

Time-dependent changes in the renal sympathetic nerve activity (RSNA) in the progression of chronic kidney disease (CKD) have not been investigated, despite the fact that renal sympathetic nervous system is augmented in the condition of CKD. In the present study, we examined time-dependent changes in RSNA and renal venous norepinephrine concentrations for 12 weeks using 5 of 6 nephrectomized CKD rats. Both RSNA and norepinephrine concentrations were increased during the early phase in the progression of CKD. Urinary protein excretion and systolic blood pressure (SBP) were gradually increased during 12 weeks after 5 of 6 nephrectomy. Treatment with γ-aminobutyric acid or the combination of prazosin and propranolol in the early phase (0-4 weeks) after 5 of 6 nephrectomy significantly attenuated the increases in urinary protein excretion and SBP in 5 of 6 nephrectomized rats. On the other hand, the same treatment in the late phase (8-12 weeks) after 5 of 6 nephrectomy failed to suppress the proteinuria and increase in SBP. Treatment with hydralazine at hypotensive dose for 12 weeks also failed to affect the proteinuria in 5 of 6 nephrectomized CKD rats. In conclusion, the augmentation of renal sympathetic nervous system in early phase after 5 of 6 nephrectomy is closely related to the development of partial ablation-induced CKD in rats.

Neurogenic and endothelial nitric oxide regulates blood circulation in lingual and other oral tissues.

Blood flow in oral tissues, including the tongue, salivary glands, gingiva, dental pulp, and lip, plays an important role in modulating the complex oral functions involved in food intake. Oral tissue circulation is regulated by nitric oxide (NO) synthesized by neuronal NO synthase mainly present in parasympathetic vasodilator neurons and also by endothelial NO sythase. Electrical stimulation of parasympathetic nerves causes vasodilatation and blood flow increase in the tongue, submandibular gland, and lip in various mammals in vitro and in vivo. Lingual arteries isolated from Japanese monkeys respond to perivascular nerve stimulation by electrical pulses and nicotine with relaxations that are mediated via neurogenic NO. There is evidence supporting the hypothesis that the superior salivatory nucleus delivers central information through the geniculate ganglion and greater petrosal nerve to the pterygopalatine ganglion, which sends off impulses through nitrergic nerves to oral tissues. Endothelial NO also plays an important role in improving oral blood circulation not only in resting conditions but also under conditions activated by chemical and physical stimuli in the tongue, submandibular and parotid glands, dental pulp/gingiva, and cheek pouch. Maintenance of health in oral circulation by minimizing factors responsible for impairment of endothelial and neurogenic NO bioavailability would be important for the prophylaxis of life-style related diseases.

Cerebral blood flow regulation by nitric oxide: recent advances.

Nitric oxide (NO) is undoubtedly quite an important intercellular messenger in cerebral and peripheral hemodynamics. This molecule, formed by constitutive isomers of NO synthase, endothelial nitric-oxide synthase, and neuronal nitric-oxide synthase, plays pivotal roles in the regulation of cerebral blood flow and cell viability and in the protection of nerve cells or fibers against pathogenic factors associated with cerebral ischemia, trauma, and hemorrhage. Cerebral blood flow is increased and cerebral vascular resistance is decreased by NO derived from endothelial cells, autonomic nitrergic nerves, or brain neurons under resting and stimulated conditions. Somatosensory stimulation also evokes cerebral vasodilatation mediated by neurogenic NO. Oxygen and carbon dioxide alter cerebral blood flow and vascular tone mainly via constitutively formed NO. Endothelial dysfunction impairs cerebral hemodynamics by reducing the bioavailability of NO and increasing the production of reactive oxygen species (ROS). The NO-ROS interaction is an important issue in discussing blood flow and cell viability in the brain. Recent studies on brain circulation provide quite useful information concerning the physiological roles of NO produced by constitutive isoforms of nitric-oxide synthase and how NO may promote cerebral pathogenesis under certain conditions, including cerebral ischemia/stroke, cerebral vasospasm after subarachnoid hemorrhage, and brain injury. This information would contribute to better understanding of cerebral hemodynamic regulation and its dysfunction and to development of novel therapeutic measures to treat diseases of the central nervous system.

Mechanisms underlying the renoprotective effect of GABA against ischemia/reperfusion-induced renal injury in rats.

The excitation of the renal sympathetic nervous system plays an important role in the development of ischemic acute kidney injury (AKI) in rats. We have reported that intravenous treatment with GABA has preventive effects on ischemia/reperfusion (I/R)-induced renal dysfunction with histological damage in rats. However, detailed mechanisms of the action of GABA on the renal injury were still unknown. Therefore, in the present study, we aimed to clarify the detailed mechanisms of GABA in ischemic AKI in rats. Ischemic AKI was induced by clamping the left renal artery and vein for 45 min. Thereafter, the kidney was reperfused to produce I/R-induced injury. Intravenous or intracerebroventricular treatment with 3-[[[(3,4-dichlorophenyl)methyl]amino]propyl] diethoxymethyl) phosphinic acid (CGP52432), a GABA(B) receptor antagonist, abolished the suppressive effects of intravenously applied GABA on enhanced renal sympathetic nerve activity during ischemia, leading to the elimination of the renoprotective effects of GABA. Intracerebroventricular treatment with GABA or intravenous treatment with baclofen, a selective GABA(B) receptor agonist, prevented I/R-induced renal injury equivalent to intravenous treatment with GABA. However, intravenous treatment with bicuculline, a GABA(A) receptor antagonist, failed to affect the preventive effects of GABA on ischemic AKI. Therefore, we demonstrated the novel finding that the preventive effect of GABA on ischemic AKI through the suppression of enhanced renal sympathetic nerve activity induced by renal ischemia is presumably mediated via GABA(B) receptor stimulation in the central nervous system rather than peripheral GABA(B) receptor.

Contribution of nitric oxide in big endothelin-1-induced cardioprotective effects on ischemia/reperfusion injury in rat hearts.

We have recently shown that an appropriate amount of exogenous big endothelin-1 (ET-1) has beneficial effects on ischemia-/reperfusion-induced norepinephrine overflow and cardiac dysfunction in rat hearts and that these effects occur through a conversion to ET-1 by endothelin-converting enzyme and following stimulation of ETB receptor. In this study, we examined the possible involvement of nitric oxide (NO) in the big ET-1-induced cardioprotective effects. According to the Langendorff technique, isolated rat hearts were subjected to 40-minute global ischemia followed by 30-minute reperfusion. Exogenous big ET-1 (0.3 nM) significantly increased NOx (NO2/NO3) level in the coronary effluent after onset of reperfusion. This effect was markedly attenuated by treatment with SM-19712 (selective endothelin-converting enzyme inhibitor), A-192621 (selective ETB receptor antagonist), or NG-nitro-l-arginine (nonselective NO synthase inhibitor), respectively. In addition, N-nitro-l-arginine blunted big ET-1-induced suppression of norepinephrine overflow and improvement of cardiac dysfunction after ischemia/reperfusion. These findings suggest that NO produced by ETB receptor activation plays an important role in exogenous big ET-1-induced actions.

Impairment by hypoxia or hypoxia/reoxygenation of nitric oxide-mediated relaxation in isolated monkey coronary artery: the role of intracellular superoxide.

To investigate the effect of hypoxia or hypoxia/reoxygenation on vascular smooth muscle function, mechanical response of monkey coronary artery without endothelium was studied under normoxia, hypoxia, and hypoxia/reoxygenation. Hypoxia or hypoxia/reoxygenation impaired the relaxation by nitroglycerin or isosorbide dinitrate but not that by 8-bromoguanosine-3',5'-cyclic monophosphate or isoproterenol. Tempol restored the impaired relaxation by nitroglycerin or isosorbide dinitrate, but superoxide dismutase had no effect. Apocynin, an NADPH oxidase inhibitor, improved the nitroglycerin-induced relaxation under hypoxia, but not under reoxygenation. Under combined treatment of apocynin with oxypurinol (xanthine oxidase inhibitor), rotenone (mitochondria electron transport inhibitor), or both, hypoxic impairment of vasorelaxation was restored more effectively. Similarly, impairment of the nitroglycerin-induced vasorelaxation under hypoxia/reoxygenation was restored by combined treatment with three inhibitors, apocynin, oxypurinol, and rotenone. Increase in superoxide production under hypoxia tended to be inhibited by apocynin and that under hypoxia/reoxygenation was abolished by combined treatment with three inhibitors. These findings suggest that increased intracellular superoxide production under hypoxia or hypoxia/reoxygenation attenuates vasodilation mediated with a nitric oxide/soluble guanylyl cyclase, but not adenylyl cyclase, signaling pathway. The main source of superoxide production under hypoxia seems to be different from that under reoxygenation: superoxide is produced by NADPH oxidase during hypoxia, whereas it is produced by xanthine oxidase, mitochondria, or both during reoxygenation.[Supplementary Figure: available only at http://dx.doi.org/10.1254/jphs.11031FP].

Postconditioning improves postischemic cardiac dysfunction independently of norepinephrine overflow after reperfusion in rat hearts: comparison with preconditioning.

We investigated whether the cardioprotective effect of ischemic postconditioning (postC) against ischemia/reperfusion (I/R)-induced cardiac dysfunction is associated with the negative control of I/R-enhanced norepinephrine (NE) overflow, an aggravating factor of I/R injury, in comparison with the effects induced by ischemic preconditioning (preC). According to the Langendorff technique, isolated rat hearts were subjected to 40-minute global ischemia followed by 30-minute reperfusion. PostC, consisting of three cycles of 30-second reperfusion followed by 30-second ischemia at the end of the 40-minute ischemia, improved I/R-induced cardiac dysfunction. However, the potency of this postC-induced improvement was somewhat weaker than that produced by preC, consisting of three cycles of 5-minute ischemia followed by 5-minute reperfusion before 40-minute ischemia. The preC treatment markedly suppressed I/R-enhanced NE overflow, whereas postC had no apparent effect. A nonselective nitric oxide synthase inhibitor, N-nitro-L-arginine, almost completely abolished postC-induced cardiac protection without affecting NE overflow, whereas the effect of preC on I/R-induced cardiac dysfunction and NE overflow was only partially inhibited by N-nitro-L-arginine. These findings indicate that the beneficial effect of postC on I/R-induced cardiac dysfunction depends on nitric oxide and is irrelevant to NE overflow after reperfusion in contrast to the preC effect.

Vascular actions of nitric oxide as affected by exposure to alcohol.

Vasodilator substances liberated from endothelial cells, mainly nitric oxide (NO), play important roles in physiologically regulating blood flow and blood pressure and preventing pathological vascular damage. Impairment of these actions promotes the genesis of cardiovascular diseases such as hypertension, cerebral and cardiac hypoperfusion, impaired vasodilatation and atherosclerosis. Low concentrations of alcohol induce increased release of NO from the endothelium due to activation and expression of NO synthase (NOS). In contrast, administration of high concentrations of alcohol or its chronic ingestion impairs endothelial functions in association with reduced NO bioavailability. The endogenous NOS inhibitor asymmetric dimethylarginine may participate in decreased synthesis of NO. Chronic alcohol intake also impairs penile erectile function possibly by interfering with endothelial, but not nitrergic nerve, function. This review article summarizes the vascular actions of NO derived from endothelial and neuronal NOS as affected by alcohol, other than wine, and acetaldehyde in healthy individuals, human materials and various experimental animals.

Effect of nitric oxide synthase inhibitor on increase in nasal mucosal blood flow induced by sensory and parasympathetic nerve stimulation in rats.

OBJECTIVES: Neural control of nasal blood flow (NBF) has not been systematically investigated. The aim of the present study was to evaluate the effect of electrical stimulation of both sensory and parasympathetic nerves innervating the nasal mucosal arteries on NBF in rats. METHODS: In anesthetized rats, nasociliary (sensory) nerves and postganglionic (parasympathetic) nerves derived from the right sphenopalatine ganglion were electrically stimulated. We measured NBF with a laser-Doppler flowmeter. RESULTS: The nerve stimulation increased NBF on both sides and increased the mean arterial blood pressure. The increase in NBF was larger on the ipsilateral side than on the contralateral side. Hexamethonium bromide, a ganglion blocker, abolished the stimulation-induced pressure effect and the increase in NBF on the contralateral side, but did not abolish the increase in NBF on the ipsilateral side. The remaining increase in NBF was abolished by N(G)-nitro-L-arginine, a nitric oxide synthase inhibitor. Histochemical analysis with nicotinamide adenine dinucleotide phosphate-diaphorase showed neuronal nitric oxide synthase-containing nerves that innervate nasal mucosal arteries. CONCLUSIONS: Nitric oxide released from parasympathetic nitrergic nerves may contribute to an increase in NBF in rats. The afferent impulses induced by sensory nerve stimulation may lead to an increase in mean arterial blood pressure that is partly responsible for the increase in NBF.

Cerebral blood flow regulation by nitric oxide in neurological disorders.

There has been a rapid increase in the amount of information on the physiological and pathophysiological roles of nitric oxide (NO) in the brain. This molecule, which is formed by the constitutive isoforms of NO synthase, endothelial (eNOS) and neuronal (nNOS), plays an obligatory role in the regulation of cerebral blood flow and cell viability and in the protection of nerve cells or fibres against pathogenic factors associated with Alzheimer's disease, Huntington's disease, seizures, and migraine. Cerebral blood flow is impaired by decreased formation of NO from endothelial cells, autonomic nitrergic nerves, or brain neurons and also by increased production of reactive oxygen species (ROS). The NO-ROS interaction is an important topic in discussing blood flow and cell viability in the brain. Excessive production of NO by inducible NOS (iNOS) and nNOS in the brain participates in neurotoxicity. Recent studies on brain circulation have provided useful information about the involvement of impaired NO availability or uncontrolled NO production in cerebral pathogenesis, including Alzheimer's disease, seizures, vascular headaches, and inflammatory disorders. Insight into the role of NO in the brain will contribute to our better understanding of cerebral hemodynamic dysfunction and will aid in developing novel therapeutic measures in diseases of the central nervous system.

Cilostazol's effect on the response to perivascular nerve stimulation in isolated dog cerebral and mesenteric arteries.

Clinical studies have demonstrated that cilostazol (CZ), an antiplatelet agent with type 3 phosphodiesterase inhibition, reduces the risk of secondary stroke. To analyze CZ's vascular action, especially in relation to endothelial and perivascular nerve functions, we examined CZ's effects on the responses to endothelial and nerve stimulation in dog cerebral arteries, and on the response to nerve stimulation in dog mesenteric arteries. Low concentrations of CZ (10(-8) and 10(-7) mol/L) failed to relax the cerebral arteries, but a higher concentration (10(-6) mol/L) relaxed them in an endothelium-independent manner. Substance P-induced relaxation was endothelium-dependent in the cerebral arteries, whereas transmural electrical stimulation (TES) and nicotine-induced relaxation were endothelium-independent. This relaxation was abolished by N(G)-nitro-L-arginine, an NO synthase (NOS) inhibitor. A lower concentration (10(-7) mol/L) of CZ enhanced the relaxation caused by nerve-derived NO but did not affect the relaxation caused by endothelium-derived NO in the cerebral arteries; moreover, it did not affect the contractions caused by nerve-derived noradrenaline in the mesenteric arteries under treatment with the NOS inhibitor. It is concluded that CZ may selectively enhance nitrergic nerve function, possibly via the activation of neuronal NOS, in dog cerebral arteries, since it does not affect the function of the noradrenergic nerve or that of endothelial NOS. Therefore, this novel vasodilatory effect of CZ may explain the reduction in the risk of secondary stroke in addition to the antiplatelet action and the direct vasodilatory action on smooth muscle.

Effects of capsaicin and nitric oxide synthase inhibitor on increase in cerebral blood flow induced by sensory and parasympathetic nerve stimulation in the rat.

Effects of electrical stimulation of the nerve bundles including sensory and parasympathetic nerves innervating cerebral arteries on cerebral blood flow (CBF) and mean arterial blood pressure (MABP) were investigated with a laser-Doppler flowmeter and a blood pressure monitoring system in anesthetized rats pretreated with and without capsaicin. The electrode was hooked on the nerve bundles including the distal nasociliary nerve from trigeminal nerve and parasympathetic nerve fibers from sphenopalatine ganglion. In control rats, the nerve stimulation for 30 s increased CBF in the ipsilateral side and MABP. Hexamethonium attenuated the increase in CBF and abolished that in MABP. Under treatment with hexamethonium, N(G)-nitro-L-arginine (L-NNA, 1 mg/kg) significantly attenuated the stimulation-induced increase in CBF, which was restored by the addition of L-arginine. Although the dose of L-NNA was raised up to 10 mg/kg, the stimulation-induced increase in CBF was not further inhibited and was never abolished. In capsaicin-pretreated rats, magnitudes of the stimulation-induced increases in CBF and MABP were lower than those in control rats. Hexamethonium attenuated the increase in CBF and abolished that in MABP. Under treatment with hexamethonium, L-NNA abolished the stimulation-induced increase in CBF in capsaicin-pretreated rats. In conclusion, nitric oxide released from parasympathetic nerves and neuropeptide(s) released antidromically from sensory nerves may be responsible for the increase in CBF in the rat. The afferent impulses by nerve stimulation may stimulate the trigeminal nerve and lead to the rapid increase in MABP, which partly contributes to the increase in CBF.

Nitric oxide modulation of endothelium-derived hyperpolarizing factor in agonist-induced depressor responses in anesthetized rats.

Vasodilators, such as prostacyclin, nitric oxide (NO), and endothelium-derived hyperpolarizing factor (EDHF), released from the vascular endothelium are important in the maintenance of systemic blood pressure. Some studies have shown that NO affects EDHF-induced vasodilator responses in isolated perfused blood vessel segments. However, the effects of NO on EDHF-mediated dilation, and their contribution to systemic blood pressure, have not been clarified. Therefore, in the present study we investigated the mechanisms underlying acetylcholine- and bradykinin-induced depressor responses, as well as the interaction between NO and EDHF, by measuring systemic blood pressure in anesthetized rats. In the presence of indomethacin and N(G)-nitro-l-arginine (l-NA; an NO synthase inhibitor), apamin plus charybdotoxin significantly inhibited depressor responses to acetylcholine and bradykinin, whereas glibenclamide, iberiotoxin, quinacrine, catalase, and combination of ouabain plus BaCl2 failed to inhibit EDHF-induced depressor responses. 4-Aminopyridine significantly inhibited depressor responses to acetylcholine, but not to bradykinin. In the presence of indomethacin and l-NA, carbenoxolone, a gap junction inhibitor, significantly inhibited depressor responses to agonists. l-NA alone significantly potentiated agonist-induced depressor responses. In contrast, infusion of sodium nitroprusside, an NO donor, or 8-br-cGMP significantly inhibited depressor responses to agonist. The findings of the present study raise the possibility that agonist-induced depressor responses are elicited by propagation of endothelial hyperpolarization via apamin- plus charybdotoxin-sensitive K(+) channels to smooth muscle cells through gap junctions, but not by diffusible substance(s). It is suggested that, in anesthetized rats, the EDHF-induced depressor response is attenuated in the presence of endogenous and exogenous NO via an increment in cGMP.

Mediation of arachidonic acid metabolite(s) produced by endothelial cytochrome P-450 3A4 in monkey arterial relaxation.

We investigated mechanisms of endothelium-dependent relaxation by acetylcholine resistant to indomethacin and N(G)-nitro-L-arginine and sensitive to cytochrome P-450 (CYP) inhibitors or charybdotoxin + apamin in the monkey lingual artery. Treatment with quinacrine, an inhibitor of phospholipase A2, abolished the relaxation by acetylcholine. However, treatment with alpha-glycyrrhetinic acid, an inhibitor of gap junctions, or catalase, an enzyme which dismutates hydrogen peroxide to form water and oxygen, did not affect the relaxation by acetylcholine. Immunohistochemistry demonstrated the presence of CYP3A4 in endothelial cells of the artery. Anti-CYP3A4 antibody inhibited relaxations by products of arachidonic acid incubated with human liver microsomes rich in CYPs in the endothelium-denuded artery. Purified CYP3A4 produced epoxyeicosatrienoic acids (EETs) from arachidonic acid, and the production was abolished by a selective CYP3A inhibitor, ketoconazole. It may be concluded that endothelium-derived relaxing substance(s) other than nitric oxide and prostanoids in the monkey lingual artery opens charybdotoxin + apamin-sensitive K+ channels in smooth muscle cells, and arachidonic acid metabolite(s) produced by endothelial CYP3A4 is likely to be the major substance.

Increased BBB permeability by parasympathetic sphenopalatine ganglion stimulation in dogs.

The blood-brain barrier (BBB) is a major obstacle for movement of large molecules to and from the brain. Stimulation of the sphenopalatine ganglion (SPG), the major source of parasympathetic innervation to brain vasculature, is known to vasodilate brain vessels, and has recently been shown to also increase the permeability of the BBB in the rat. In this work, we studied the effect of SPG stimulation on BBB permeability in larger animals--Beagle dogs. Left SPG was exposed by lateral approach in five Beagle dogs, and stimulated at 10 Hz. FITC labeled 10 kDa dextran was continuously infused to the left atrium during stimulation, and cerebral angiography was periodically obtained via the vertebral artery. Three control dogs received labeled dextran, without SPG exposure or stimulation. Brains were perfused with saline thoroughly at the end of stimulation, and samples from various regions were taken for fluorescence reading of tissue homogenates. Cerebral vasodilatation was evidenced in all but one dog, whose fluorescence results were consequently excluded from analysis, assuming that its SPG had been damaged by surgery. Fluorescence was significantly higher in the four stimulated compared to the three non-stimulated animals; e.g. mean FITC-dextran concentration in the anterior brain regions was 0.98+/-0.12 ug (mean+/-S.D.) FITC/g brain for experimental animals, and 0.40+/-0.02 for controls (p<0.01). No effect was seen in the pons and cerebellum (0.68+/-0.22 vs. 0.60+/-0.03, NS) whose vascular innervation is supplied by the otic rather than the SPG ganglion. SPG stimulation appears to be an effective way to increase BBB permeability, allowing introduction of large molecules to the brain. This could be a therapeutic method for a wide variety of brain disorders, including tumors and neurodegenerative diseases.

Mechanisms underlying endothelium-dependent flow increase in perfused rat mesenteric vascular bed.

The isolated rat mesenteric vasculature was perfused at constant pressures of 40, 80 or 120 mm Hg and the change in flow rate was measured. In the presence of phenylephrine, treatment with 3-[(3-cholamidopropyl) dimethylammonio]-1-propane sulfonate (CHAPS) or N(G)-nitro-L-arginine (L-NA) significantly inhibited the pressure-dependent flow rate increase, but treatment with indomethacin or charybdotoxin plus apamin did not. Acetylcholine, bradykinin and ADP increased the flow rate, which had been markedly suppressed by CHAPS. At 80 mm Hg, the flow rate increase induced by these agonists was not affected by indomethacin plus L-NA, but was suppressed by subsequent treatment with charybdotoxin plus apamin. Changes in the perfusion pressure did not significantly affect the flow rate increases induced by the agonists. In conclusion, the opening of charybdotoxin plus apamin-sensitive Ca(2+)-dependent K(+) channels may be mainly involved in the endothelium-dependent flow rate increase induced by the agonists, whereas nitric oxide (NO) may be responsible for the endothelium-dependent, pressure-induced flow rate increase.

Mechanisms underlying endothelium-dependent, nitric oxide- and prostanoid-independent relaxation in monkey and dog coronary arteries.

We compared the mechanisms of vasorelaxation of acetylcholine and of substance P with reference to K(+) channels, and analyzed pharmacologically the nature of endothelium-derived substance(s) other than NO and prostanoids in monkey and dog coronary arteries. Coronary arteries were isolated from monkeys and dogs, and the isometric tension of the artery strips was measured. In canine coronary artery strips treated with indomethacin plus N(G)-nitro- L-arginine ( L-NA) and partially contracted with prostaglandin F(2alpha), acetylcholine induced concentration-related relaxation, which was abolished by removal of the endothelium. The relaxation was markedly suppressed but not abolished in the strips exposed to high K(+) media. Charybdotoxin plus apamin potently inhibited the relaxation to the similar extent to that by high K(+) media, whereas glibenclamide or iberiotoxin had no effect. The relaxation was markedly inhibited by quinacrine, a phospholipase A(2) inhibitor, and ketoconazole, a selective cytochrome P450 (CYP) 3A inhibitor, but not by sulfaphenazole, a selective CYP 2C inhibitor. In contrast to acetylcholine, endothelium-dependent and indomethacin-plus- L-NA-resistant relaxation induced by substance P was not inhibited by high K(+) media, charybdotoxin plus apamin, or ketoconazole. Quinacrine and AA861, a 5-lipoxygenase inhibitor, inhibited the relaxation induced by substance P. In monkey coronary artery, acetylcholine-induced relaxation resistant to indomethacin plus L-NA was abolished by endothelial denudation and by treatment with high K(+) media, charybdotoxin plus apamin, progesterone and ketoconazole, but was not affected by iberiotoxin or sulfaphenazole. Substance P did not relax monkey coronary arteries. It is concluded that endothelium-dependent, nitric oxide- and prostanoid-independent relaxation induced by acetylcholine in monkey and dog coronary arteries are mediated by charybdotoxin plus apamin-sensitive but iberiotoxin-insensitive Ca(2+)-activated K(+) channel opening substance(s), which may be CYP3A-derived arachidonic acid metabolite(s). Contrasting to the response to acetylcholine, endothelium-dependent, indomethacin-plus- L-NA-resistant relaxation induced by substance P in dog coronary artery is not associated with K(+) channel opening, and may be mediated by 5-lipoxygenase product(s).

Comparison of the responses to thrombin in monkey renal and uterine arteries.

OBJECTIVE: Thrombin is known to regulate vascular tone. We analyzed and compared mechanisms of thrombin action in primate renal and uterine arteries. METHODS: Isolated Japanese monkey renal and uterine arteries were suspended in Ringer-Locke solution for tension recordings. RESULTS: Renal arteries responded to thrombin with relaxation, which was inhibited by N(G)-nitro-L-arginine or indomethacin and reversed to contractions by the combination. The relaxations were also reversed to contractions by endothelial denudation. Conversely, thrombin caused uterine arterial contractions that were unaffected by endothelial denudation. Relaxations in both renal arteries and contractions in uterine arteries were suppressed by hirudin (a specific thrombin inhibitor). Relaxant responses to A23187 (Ca(2+) ionophore), nitroprusside sodium (nitric oxide donor), and beraprost sodium (prostacyclin analogue) did not differ between renal and uterine arteries. CONCLUSION: Thrombin-induced relaxation of renal arteries appears to be mediated by nitric oxide and vasodilator prostaglandins liberated from the endothelium, whereas uterine arterial contraction is caused by an endothelium-independent mechanism.