Renin-Angiotensin-Aldosterone System Inhibitors Prevent the Onset of Oxaliplatin-Induced Peripheral Neuropathy: A Retrospective Multicenter Study and in Vitro Evaluation.

Oxaliplatin (OXA) is used in chemotherapy for various cancer types and is associated with acute and chronic neurotoxicity. However, a preventive strategy for OXA-induced peripheral neuropathy (OIPN) and its underlying mechanism remain unclear. We examined the effects of renin-angiotensin-aldosterone system inhibitors (RAASIs) on OIPN by performing a retrospective multicenter study and an in vitro assay. We retrospectively evaluated electronic medical records of 976 patients who underwent one or more courses of OXA-containing regimens at Ehime, Okayama, and Tokushima University Hospitals. The primary endpoint was the incidence of OIPN during or after OXA administration. The effects of RAASIs and OXA on the neurite length in PC12 cells were determined. The combined administration of an OXA-containing regimen and RAASI significantly inhibited the cumulative incidence grade-2 or higher OIPN (log-rank test; p = 0.0001). RAASIs markedly suppressed the development of both acute and chronic OIPN (multivariate analysis; p = 0.017 and p = 0.011). In an in vitro assay, 10 µM OXA suppressed the neurite length; treatment with 1 µM aliskiren, spironolactone, 10 µM candesartan, and enalapril significantly restored neurite length to the control level. Moreover, 1 µM SCH772984 (a selective inhibitor of extracellular signal-regulated kinase, ERK1/2) and 500 µM SQ22536 (a cell-permeable adenylate cyclase (AC) inhibitor) markedly abolished neurite-extending effects of candesartan and enalapril. These results indicate that RAASIs possess preventive or therapeutic effects in acute and chronic OIPN, candesartan and enalapril may increase in the activity of ERK1/2 and AC in PC12 cells.

Regulatory effects of nicotine on neurite outgrowth in rat superior cervical ganglia cells.

We have reported that nicotine has a neurotrophic action on peripheral adrenergic nerves in vivo, which is mediated by α7 nicotinic acetylcholine receptors (nAChRs). To clarify the possible mechanisms, the present study further investigated the effect of nicotine on neurite outgrowth in tyrosine hydroxylase (TH)-positive superior cervical ganglia (SCG) cells isolated from neonatal rats in vitro. Nicotine at low concentrations (0.01-0.3 mM) increased the number of neurite outgrowths in TH-immunopositive SCG cells, while high concentrations of nicotine (1-10 mM) gradually reduced it, and only 10 mM nicotine was markedly inhibited compared to the control. A 100 µM of nicotine-induced increase in neurite numbers depended on the exposure time and was inhibited by treatment with the nAChR antagonist hexamethonium (Hex) and α7 nAChR antagonist α-bungarotoxin (α-Bgtx). The nicotine (10 mM)-induced a significant decrease in neurite outgrowth in SCG, which was perfectly canceled by Hex to the control level but not by α-Bgtx. These results suggest that nicotine has a regulatory neurotrophic action mediated by both α7 nAChR and other subtypes in TH-positive SCG cells of rats.

Charge-separated spectra of suprathermal highly charged bismuth ions in a dual laser-produced plasma soft x-ray source.

We investigated the charge-separated spectra of highly charged suprathermal bismuth (Bi) ions from a dual laser-produced plasma soft x-ray source developed for soft x-ray microscopy. The charge distribution of these suprathermal ions emitted from a solid planar Bi target was measured by an electrostatic energy analyzer. The maximum ionic charge state was observed to be Z = 17 and to possess a maximum energy of about 200 keV. This evaluation provides important information essential for the development of debris mitigation schemes in a soft x-ray microscope.

Oral administration of Eucommia ulmoides Oliv. leaves extract protects against atherosclerosis by improving macrophage function in ApoE knockout mice.

Eucommia leaf extract (ELE) is a traditional Chinese herbal medicine. We investigated the effect of ELE on the development of atherosclerosis and changes in peritoneal macrophage function in apolipoprotein E knockout (ApoE-/- ) mice. At 8 weeks of age, ApoE-/- mice were randomly divided into three groups that were fed a high-fat diet blended with 0% (control), 5% or 10% ELE for a period of 7 weeks. The 10% ELE dose caused an approximately 36% reduction in atherosclerotic lesions, as estimated by oil red O staining. Real-time PCR analysis showed that the 1-week treatment with ELE reduced mRNA levels of Tnf-alpha, Il-1, and Mif in peritoneal macrophages isolated from the ApoE-/- mice. Furthermore, a 1-week treatment with the 10% ELE diet significantly reduced migration and adhesion functions in peritoneal macrophages. These results suggest that a 10% ELE diet reduces atherosclerotic lesions and modulates macrophage function by reducing cytokine expression. PRACTICAL APPLICATION: Eucommia leaf extract (ELE) is a traditional Chinese herbal medicine that reduces atherosclerotic lesions and suppresses inflammatory cytokines expression.

Soft X-ray spectral analysis of laser produced molybdenum plasmas using the fundamental and second harmonics of a Nd:YAG laser.

Our measurement of the soft X-ray emission of Mo plasmas produced by picosecond Nd:YAG lasers emitting on the fundamental (1064 nm, 150 ps) and second (532 nm, 130 ps) harmonics is presented. The contrast in intensity between spectral peaks and the intensity outside them is lower for the second harmonic produced plasmas probably due to the presence more intense satellite emission and higher optical thickness. The measured spectra are absolutely calibrated and the observed output photon flux was (7 - 9) × 1013 photons/sr in the water-window (2.3 - 4.4 nm) spectral range for a laser energy of 160 mJ independent of laser wavelength. However, in the short wavelength range 1.5 - 2 nm, the emission using the second harmonic is strongly enhanced and is even higher than for the maximum energy of 220 mJ of the fundamental wavelength, so despite inevitable energy losses, laser wavelength conversion may lead to emission enhancement in certain spectral ranges. This enhancement is attributed to higher absorption of short wavelength laser light and higher charge state generation in denser plasmas.

Nerve growth factor (NGF) has an anti-tumor effects through perivascular innervation of neovessels in HT1080 fibrosarcoma and HepG2 hepatitis tumor in nude mice.

This study investigated whether NGF prevents tumor growth by promoting neuronal regulation of tumor blood flow. HT1080 fibrosarcoma cells or HepG2 hepatitis cells were subcutaneously implanted into nude mice. On Day 21 after the implantation of tumor cells, human NGF (40 or 80 ng/h for 14 days) was administered using a micro-osmotic pump. Growth rates of both tumors were significantly inhibited by the treatment of NGF, and the survival rate was also extended. Significant suppression of HT1080 tumor growth lasted after withdrawing NGF. NGF markedly increased the density of α-smooth muscle actin (α-SMA)-immunoreactive (ir) cells without changing neovessel density in HT1080 tumor tissues. Double immunostaining demonstrated protein gene product (PGP) 9.5-ir nerves around α-SMA-ir cells were found in HT1080 tumor tissue treated with NGF. The blood flow in HepG2 tumors treated with saline was significantly higher than in the non-tumor control area, but the tumor blood flow was markedly reduced by NGF treatment. In in vitro studies, NGF significantly accelerated migration of aortic smooth muscle cells but not endothelial cells, whereas NGF had no cytotoxic action on both cells. NGF inhibits tumor growth via indirect action, probably through innervation and maturation of tumor neovasculature, which regulates blood flow into tumor tissues.

Emission of water-window soft x-rays under optically thin conditions using low-density foam targets.

The effect of optical thickness in a bismuth water-window soft x-ray source is considered by comparing the emission from laser-produced plasmas of a 7.5% atomic density foam target and a solid-density target. The number of photons recorded in the 4 nm region was comparable for both targets at a plasma-initiating laser pulse duration of 6 ns. From experiments at different pulse durations of 150 ps and 6 ns, self-absorption (opacity) effects were found to be relatively small for bismuth plasmas as compared to those of tin, based on the same emission mechanism and which are used in 13.5 nm sources for extreme ultraviolet lithography.

Three-dimensional measurement of an inner surface profile using a supercontinuum beam.

We demonstrate an inner surface profile measurement that has a smooth spatial distribution. A supercontinuum beam suppresses the speckle contrast to 22% and the standard deviation of the point cloud to 40%, compared to equivalent values obtained by use of a conventional green He-Ne laser at a wavelength of 543.5 nm. A compact probe for the inner surface profile measurements using the supercontinuum beam measures the depth removed by wear of a small hole in an automobile component. The radial spatial resolution was evaluated to be 2 µm, which was of the same order as the wavelength of the supercontinuum beam. The supercontinuum beam enables fivefold improvement of the radial spatial resolution compared to the monochromatic wavelength beam because of a reduction in speckle effects.

Preventive Effects of Renin-angiotensin System Inhibitors on Oxaliplatin-induced Peripheral Neuropathy: A Retrospective Observational Study.

PURPOSE: Oxaliplatin-induced peripheral neuropathy has remained an unresolved issue in clinical practice. Our previous study hypothesized that inhibition of the renin-angiotensin system (RAS) may produce a preventive effect on oxaliplatin-induced neuropathy. The aim of this study was to clarify whether RAS inhibitors prevent oxaliplatin-induced peripheral neuropathy. METHODS: This study retrospectively analyzed data from cancer patients who had received chemotherapy including oxaliplatin and were treated with or without RAS inhibitors. This retrospective observational study was conducted at Ehime University Hospital using electronic medical records from May 2009 to December 2016. The primary end point was the incidence of severe peripheral neuropathy during or after oxaliplatin treatment, according to the Common Terminology Criteria for Adverse Events, version 4.0. A multivariate Cox proportional hazards model analysis was used to identify risk factors. FINDINGS: A total of 150 patients were included in the study. The estimated incidence of peripheral neuropathy was 36.9% and 91.7% in the RAS inhibitor group and the non-RAS inhibitor group, respectively. The multivariate analysis using a Cox proportional hazards model showed that the RAS inhibitor group was slightly associated with a decreased risk of neurotoxicity (adjusted hazard ratio, 0.42 [95% CI, 0.18-0.99]; P = 0.048). IMPLICATIONS: The present findings suggest that RAS inhibitors have the ability to prevent oxaliplatin-induced peripheral neuropathy.

Effect of Eucommia ulmoides Leaf Extract on Chronic Dextran Sodium Sulfate-Induced Colitis in Mice.

Ulcerative colitis (UC) is a refractory disease that causes chronic inflammation or ulceration in the mucosa of the large intestine with multiple relapses. Although several drugs, including 5-aminosalicylic acid, steroids, immunosuppressants, and infliximab, are used for UC therapy, patients suffer from side effects of these drugs, and a new safer therapeutic agent is desired. Eucommia ulmoides OLIV. leaf extract (ELE) has an anti-inflammatory effect. Therefore, we examined the effect of ELE on UC using a chronic dextran sulfate sodium (DSS)-induced colitis model in mice. Chronic DSS-induced colitis was triggered by alternately repeating 5 days' DSS and 7 days' water administration in mice for 29 d. The severity of DSS-induced colitis was evaluated by daily body weight and bloody stool score, and colon length and myeloperoxidase (MPO) activity in colon tissue on day 29. ELE (3 or 9%) was administered in combination by feeding for 29 d, and the effect on colitis was evaluated. The mice given DSS exhibited chronic colitis symptoms with body weight loss, increased bloody stool score and MPO activity, and shortened colon length. Administration of 3 or 9% ELE suppressed the body weight loss, bloody stool score, colon shortening, and MPO activity in a dose-dependent manner. Histological analysis showed that the ELE-treated mice had less damages and leukocyte infiltration in the mucosal layer of the large intestine compared to DSS alone group. These results suggested that ELE has the potential to prevent the development of DSS-induced colitis and a therapeutic effect on UC in a safe manner.

Effect of Nerve Growth Factor on Innervation of Perivascular Nerves in Neovasculatures of Mouse Cornea.

Angiogenesis, which is the generation of new vascular networks from existing blood vessels, occurs under normal and pathophysiological conditions. Perivascular nerves, which innervate mature vasculatures, maintain vascular tone and regulate tissue blood flow. However, little is known whether perivascular nerves innervate newborn blood vessels. Therefore, the aim of this study was to investigate the distribution and characterization of perivascular nerves in neovasculatures, which were generated by the mouse corneal micropocket method. Under anesthesia, a pellet containing basic fibroblast growth factor (bFGF) (100 ng/pellet) was implanted into a mouse cornea in one side of the eyeball. Nerve growth factor (NGF) was locally (2 or 20 ng) applied with the pellet, or subcutaneously (40 ng/h for 7 d) administered with an osmotic mini-pump. After the implantation, vascular endothelial cells, smooth muscle cells, and perivascular nerves in the cornea were immunohistochemically studied. Neovessels generated from existing limbal vessels were observed in pellet-implanted cornea. Immunostaining of neovasculatures showed the presence of CD31-like immunoreactive (LI) endothelial cells and α-smooth muscle actin-LI vascular smooth muscles. Perivascular nerves immunostained by protein gene product (PGP) 9.5, an axonal marker, were found in the existing limbal vessels, but they were not observed in neovasculatures. Local and subcutaneous treatment of NGF inhibits bFGF-derived angiogenesis and resulted in loop-shaped vessels that had many anastomoses, and produced innervation of PGP 9.5-LI perivascular nerves around bFGF-derived neovessels. These findings suggest that neovasculatures have no innervation of perivascular nerves, and that NGF facilitates innervations of perivascular nerves to regulate the blood flow in neovessels.

Effects of endogenous nitric oxide on adrenergic nerve-mediated vasoconstriction and calcitonin gene-related peptide-containing nerve-mediated vasodilation in pithed rats.

Vascular adrenergic nerves mainly regulate the tone of blood vessels. Calcitonin gene-related peptide-containing (CGRPergic) vasodilator nerves also participate in the regulation of vascular tone. Furthermore, there are nitric oxide (NO)-containing (nitrergic) nerves, which include NO in blood vessels as vasodilator nerves, but it remains unclear whether nitrergic nerves participate in vascular regulation. The present study investigated the role of nitrergic nerves in vascular responses to spinal cord stimulation (SCS) and vasoactive agents in pithed rats. Wistar rats were anesthetized and pithed, and vasopressor responses to SCS and injections of norepinephrine were observed. To evaluate vasorelaxant responses, the BP was increased by a continuous infusion of methoxamine with hexamethonium to block autonomic outflow. After the elevated BP stabilized, SCS and injections of acetylcholine (ACh), sodium nitroprusside (SNP), and CGRP were intravenously administered. We then evaluated the effects of the NO synthase (NOS) inhibitor, N-ω-nitro-L-arginine methylester hydrochloride (L-NAME), on these vascular responses. Pressor responses to SCS and norepinephrine in pithed rats were enhanced by L-NAME, while the combined infusion of L-NAME and L-arginine had no effect on these responses. L-NAME infusion significantly increased the release of norepinephrine evoked by SCS. In pithed rats with artificially increased BP and L-NAME infusion, depressor response to ACh (except for 0.05nmol/kg) was suppressed and SNP (only 2nmol/kg) was enhanced. However, depressor responses to SCS and CGRP were similar to control responses. The present results suggest endogenous NO regulates vascular tone through endothelium function and inhibition of adrenergic neurotransmission, but not through CGRPergic nerves.

Nerve Growth Factor Facilitates the Innervation of Perivascular Nerves in Tumor-Derived Neovasculature in the Mouse Cornea.

BACKGROUND: Tumor neovascular vessels are not innervated by perivascular nerves. This study was an investigation of the effects of the nerve growth factor (NGF) on the distribution of perivascular nerves and neovessel formation in tumor tissues. METHODS: A gel containing DU145 prostate carcinoma cells or HT1080 fibrosarcoma cells was implanted into mouse corneas. NGF was subcutaneously administered using an osmotic mini-pump. The distribution of perivascular nerves in mouse corneas and densities of CD31-immunopositive neovessels and smooth muscles (α-smooth muscle actin, α-SMA) in tumor tissues were quantified. SUMMARY: Neovessels generated from corneal limber arteries in tumor tissues were observed 4-14 days after the implantation of tumor cells. The density of CD31-immunopositive cells in endothelium increased after the implantation of DU145 or HT1080 cells, while that of α-SMA-immunopositive cells slightly increased. The NGF treatment significantly increased the density of α-SMA- but not that of CD31-immunopositive cells (except for DU145 cells) and resulted in the innervation of perivascular nerves around tumor-derived neovessels, whereas no innervation was observed in the control group. Key Messages: These results suggest that NGF facilitates the innervation of perivascular nerves to regulate blood flow into tumor-derived neovessels.

Nerve growth factor facilitates perivascular innervation in neovasculatures of mice.

It is well known that blood vessels including arterioles have a perivascular innervation. It is also widely accepted that perivascular nerves maintain vascular tone and regulate blood flow. Although there are currently prevailing opinions, unified views on the innervation of microcirculation in any organs have not been established. The present study was designed to investigate whether there are perivascular nerves innervated in microvessels and neovessels. Furthermore, we examined whether nerve growth factor (NGF) can exert a promotional effect on perivascular nerve innervation in neovessels of Matrigel plugs. A Matrigel was subcutaneously implanted in mouse. The presence of perivascular nerves in Matrigel on Day 7-21 after the implantation was immunohistochemically studied. NGF or saline was subcutaneously administered by an osmotic mini-pump for a period of 3-14 days. The immunostaining of neovasculatures in Matrigel showed the presence of perivascular nerves on Day 21 after Matrigel injection. Perivascular nerve innervation of neovessels within Matrigel implanted in NGF-treated mice was observed in Day 17 after Matrigel implantation. However, NGF treatment did not increase numbers of neovessels in Matrigel. These results suggest that perivascular nerves innervate neovessels as neovasculatures mature and that NGF accelerates the innervation of perivascular nerves in neovessels.

Vascular responses to compound 48/80 in rat mesenteric vascular beds.

A further investigation was performed on the vascular effect of endogenous histamine using the histamine releaser, compound 48/80, in rat mesenteric vascular beds with active tone. In preparations with intact endothelium, low concentrations of compound 48/80 (1.53 × 10(-5) - 3 × 1.53 × 10(-5) mg/mL) perfusion for 1 min only induced a small vasodilation. High concentrations of compound 48/80 (1.53 × 10(-4) - 3 × 1.53 × 10(-2) mg/mL) induced a biphasic vascular responses, an initial vasoconstriction followed a subsequent long-lasting vasodilation. The vasodilation induced by low concentrations of compound 48/80 and the vasoconstriction induced by high concentration of compound 48/80 was inhibited by olopatadine. However, cimetidine did not affect the responses induced by compound 48/80. Endothelium removal enlarged the compound 48/80-induced phase-2 vasoconstriction, while it attenuated the phase-3 vasodilation. Additionally, indomethacin and seratrodast significantly inhibited vasoconstriction but it did not affect the long-lasting vasodilation induced by high concentrations of compound 48/80. Ruthenium red inhibited the vasodilation induced by low concentrations and high concentrations of compound 48/80. These results suggest that the vasoconstriction induce by high concentrations of compound 48/80 is mediated by endogenous histamine released from mast cells. It is also suggested that thromboxane A2 released from mast cells is related to the vasoconstriction.

Muscarinic acetylcholine receptor M1 and M3 subtypes mediate acetylcholine-induced endothelium-independent vasodilatation in rat mesenteric arteries.

The present study investigated pharmacological characterizations of muscarinic acetylcholine receptor (AChR) subtypes involving ACh-induced endothelium-independent vasodilatation in rat mesenteric arteries. Changes in perfusion pressure to periarterial nerve stimulation and ACh were measured before and after the perfusion of Krebs solution containing muscarinic receptor antagonists. Distributions of muscarinic AChR subtypes in mesenteric arteries with an intact endothelium were studied using Western blotting. The expression level of M1 and M3 was significantly greater than that of M2. Endothelium removal significantly decreased expression levels of M2 and M3, but not M1. In perfused mesenteric vascular beds with intact endothelium and active tone, exogenous ACh (1, 10, and 100 nmol) produced concentration-dependent and long-lasting vasodilatations. In endothelium-denuded preparations, relaxation to ACh (1 nmol) disappeared, but ACh at 10 and 100 nmol caused long-lasting vasodilatations, which were markedly blocked by the treatment of pirenzepine (M1 antagonist) or 4-DAMP (M1 and M3 antagonist) plus hexamethonium (nicotinic AChR antagonist), but not methoctramine (M2 and M4 antagonist). These results suggest that muscarinic AChR subtypes, mainly M1, distribute throughout the rat mesenteric arteries, and that activation of M1 and/or M3 which may be located on CGRPergic nerves releases CGRP, causing an endothelium-independent vasodilatation.

Factors Contributing to the Clinical Effectiveness of the DPP-4 Inhibitor Sitagliptin in Patients With Type 2 Diabetes.

PURPOSE: Treatment with dipeptidyl peptidase 4 (DPP-4) inhibitors may have responders or nonresponders. However, agreement on the effects of patient background and/or contributory factors that have a negative effect on the efficacy of DPP-4 inhibitors is lacking. The aim of the present study was to investigate the effect of resistance factors on the clinical efficacy of sitagliptin (SITA) for patients with type 2 diabetes. METHODS: We performed a retrospective study based on the medical records of patients who were treated with SITA alone (SITA-A; n = 16), a combination of a sulfonylurea (SU) without a change in dose and add-on SITA (SU + SITA; n = 29), SITA alone after the discontinuation of premedication with antidiabetic agents (SITA-AD; n = 18), or a combination of an SU with a dose reduction and SITA (L-SU + SITA; n = 17). Multivariate logistic regression analysis was employed to estimate the influence of resistance factors on hemoglobin (Hb) A1c lowering by SITA treatment for 3 months. FINDINGS: The HbA1c levels were significantly lower after 3-month treatment with SITA-A (6.3% [0.2%]), SU + SITA (7.1% [0.2%]), and L-SU + SITA (6.6% [0.2%]), but not with SITA-AD (6.3% [0.2%]), than baseline levels before treatment. Multivariate logistic regression analysis established that a decreased efficacy of SITA was markedly related to baseline HbA1c levels of ≥7.5% and dyslipidemia. IMPLICATIONS: These results suggest that checking for the presence or absence of resistance factors, including elevated HbA1c levels and dyslipidemia, may contribute to the appropriate usage of SITA.

Nerve growth factor facilitates redistribution of adrenergic and non-adrenergic non-cholinergic perivascular nerves injured by phenol in rat mesenteric resistance arteries.

We previously reported that nerve growth factor (NGF) facilitated perivascular sympathetic neuropeptide Y (NPY)- and calcitonin gene-related peptide (CGRP)-containing nerves injured by the topical application of phenol in the rat mesenteric artery. We also demonstrated that mesenteric arterial nerves were distributed into tyrosine hydroxylase (TH)-, substance P (SP)-, and neuronal nitric oxide synthase (nNOS)-containing nerves, which had axo-axonal interactions. In the present study, we examined the effects of NGF on phenol-injured perivascular nerves, including TH-, NPY-, nNOS-, CGRP-, and SP-containing nerves, in rat mesenteric arteries in more detail. Wistar rats underwent the in vivo topical application of 10% phenol to the superior mesenteric artery, proximal to the abdominal aorta, under pentobarbital-Na anesthesia. The distribution of perivascular nerves in the mesenteric arteries of the 2nd to 3rd-order branches isolated from 8-week-old Wistar rats was investigated immunohistochemically using antibodies against TH-, NPY-, nNOS-, CGRP-, and SP-containing nerves. The topical phenol treatment markedly reduced the density of all nerves in these arteries. The administration of NGF at a dose of 20µg/kg/day with an osmotic pump for 7 days significantly increased the density of all perivascular nerves over that of sham control levels. These results suggest that NGF facilitates the reinnervation of all perivascular nerves injured by phenol in small resistance arteries.

Characterization of Perivascular Nerve Distribution in Rat Mesenteric Small Arteries.

The distribution pattern of perivascular nerves in some branches of rat mesenteric arteries was studied. Mesenteric arteries isolated from 8-week-old Wistar rats were divided into the 1st-, 2nd-, and 3rd-order branches. The distribution of perivascular nerves in each branch was immunohistochemically evaluated using antibodies against neuropeptide Y (NPY), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), and neuronal nitric oxide synthase (nNOS). The density of NPY-, TH-, CGRP-, and SP-like immunoreactive (LI) nerves in the 2nd and 3rd branches was significantly greater than that in the 1st branch, and a negative relationship was found between nerve density and arterial diameter, except for TH-LI nerves. The density of NPY- and TH-LI nerves in all branches, which was similar, was greater than that of CGRP- (except for NPY-LI nerves in the 1st branch), SP-, or nNOS-LI nerves. Double immunostaining revealed that TH-LI nerves made contact with nNOS-LI, CGRP-LI, and SP-LI nerves and that CGRP-LI nerves made contact with TH-, NPY-, or nNOS-LI nerves, while TH-LI and CGRP-LI nerves nearly merged with NPY-LI and SP-LI nerves, respectively. These results suggest that the each branch of mesenteric arteries is densely innervated by vasoconstrictor nerves containing NPY, TH, and vasodilator CGRP nerves. They also suggest that the intense density of perivascular nerves in the 2nd and 3rd branches may contribute to maintaining vascular tone.

Nicotine facilitates reinnervation of phenol-injured perivascular adrenergic nerves in the rat mesenteric resistance artery.

Nicotine has been shown to have neuroprotective and neurotrophic actions in the central nervous system. To elucidate the peripheral neurotrophic effects of nicotine, we determined whether nicotine affected the reinnervation of mesenteric perivascular nerves following a topical phenol treatment. A topical phenol treatment was applied to the superior mesenteric artery proximal to the abdominal aorta in Wistar rats. We examined the immunohistochemistry of the distal small arteries 7 days after the treatment. The topical phenol treatment markedly reduced the density of tyrosine hydroxylase (TH)-LI and calcitonin gene-related peptide (CGRP)-LI fibers in these arteries. The administration of nicotine at a dose of 3 mg/kg/day (1.5 mg/kg/injection, twice a day), but not once a day or its continuous infusion using a mini-pump significantly increased the density of TH-LI nerves without affecting CGRP-LI nerves. A pretreatment with nicotinic acetylcholine receptor antagonists hexamethonium, mecamylamine, and methyllycaconitine, but not dextrometorphan, canceled the TH-LI nerve reinnervation induced by nicotine. Nicotine significantly increased NGF levels in the superior cervical ganglia (SCG) and mesenteric arteries, but not in the dorsal root ganglia, and also up-regulated the expression of NGF receptors (TrkA) in the SCG, which were canceled by hexamethonium. These results suggested that nicotine exhibited neurotrophic effects that facilitated the reinnervation of adrenergic TH-LI nerves by activating α7 nicotinic acetylcholine receptor and NGF in the SCG.