Bilateral analgesic effects of abobotulinumtoxinA (Dysport® ) following unilateral administration in the rat.

BACKGROUND: In addition to inhibition of muscle and glandular hyperactivity, botulinum neurotoxin (BoNT) type A also interferes with pain processing. Previously, in a rat model of paclitaxel-induced polyneuropathy, abobotulinumtoxinA (aboBoNT-A) elicited analgesic effects not only in the injected paw, but also in the contralateral, non-injected paw. METHODS: Here, we assessed bilateral analgesic effects of unilateral aboBoNT-A in several chronic pain models in Sprague-Dawley rats. Effects of aboBoNT-A on the paw withdrawal threshold in response to mechanical pressure was assessed in models of streptozotocin-induced diabetic polyneuropathy, chronic constriction injury (CCI)-associated mononeuropathy, and bilateral carrageenan-induced inflammatory pain. RESULTS: In diabetic polyneuropathy, aboBoNT-A (15, 20 U/kg) reversed hyperalgesia in the toxin-injected and non-injected paws. In unilateral CCI-exposed animals, 20 U/kg aboBoNT-A given ipsilateral to the injury reversed mechanical hyperalgesia, while 30 U/kg aboBoNT-A given contralateral to the injury had no effect. In carrageenan-induced bilateral inflammatory pain, aboBoNT-A (20, 30 U/kg) reversed hyperalgesia in both toxin-injected and non-injected paws. DISCUSSION: These results suggest that unilateral administration of aboBoNT-A results in bilateral reduction in mechanical hyperalgesia across neuropathic and inflammatory pain conditions, bilateral activation of sensory neurons being prerequisite for its expression. Future studies involving effects on other sensory modalities as well as those evaluating diffusion and migration of the toxin away from the injection site can shed light on mechanisms of this phenomenon. SIGNIFICANCE: The results expand evidence on bilateral analgesic effects of aboBoNT-A following unilateral administration across pain modalities, as the phenomenon is seen in more than one model of polyneuropathy as well as in a model of chronic inflammatory pain when the latter is rendered bilateral. The mechanism of bilateral analgesic effects of aboBoNT-A may require activation of the peripheral sensory neurons and involve retrograde axonal transport of the toxin into the spinal cord.

[Therapeutic strategies and Alzheimer's disease: contribution of animal models]. / Stratégies thérapeutiques et maladie d'Alzheimer : que peuvent apporter les modèles animaux ?

Alzheimer's disease (AD) is a human neurodegenerative disease characterized by two key histopathological hallmarks : beta amyloid plaques and neurofibrillary tangles. No animal species naturally develops AD. Lesions induced by toxic substances which modify neurotransmission have been used in rodents but are not suitable models for AD. More recently, transgenic mouse models reproducing physiopathologic aspects of AD have greatly contributed to our understanding of the disease and have provided models to evaluate new therapeutic approaches. While none of these models perfectly reproduces all the pathological characteristics of AD, they are extremely useful in the evaluation and development of novel therapeutic agents. Pharmacological evaluation should assess abnormal behavior, histopathologic lesions and biochemical or metabolic dysfunctions. New technologic tools such as neuroimaging and biological biomarkers have greatly facilitated these evaluations. Depending on the symptomatic or neuroprotective therapeutic objectives, these methods are becoming increasingly accurate and adaptable to the human patient. A multidisciplinary approach is going to optimize these models so that they can become more predictive and help bring forward new effective treatments for AD patients.

BN 80933 inhibits F2-isoprostane elevation in focal cerebral ischaemia and hypoxic neuronal cultures.

Formation of the lipid peroxidation product 8-epi-prostaglandin2alpha (8-epi-PGF2alpha) a bioactive marker of oxidative stress, was quantified in in vitro and in vivo models of neuronal death. In culture media of primary rat cortical neurones exposed to hypoxia followed by reoxygenation, a 3.7-fold increase of 8-epi-PGF2alpha concentration was observed in comparison to control cells. In rats submitted to 2h middle cerebral artery occlusion followed by a 22h reperfusion period, a 27-fold increase of 8-epi-PGF2alpha was observed in the ischaemic hemisphere compared with the corresponding hemisphere of sham-operated rats. Treatment with the neuroprotective agent BN 80933 significantly reduced both 8-epi-PGF2alpha elevations in vitro and in vivo. These data suggest that 8-epi-PGF2alpha elevations might reflect the damaging free radical overproduction and subsequent lipid peroxidation during neuronal injury induced by hypoxia and ischaemia. Inhibition of 8-epi-PGF2alpha elevations participates to the neuroprotective effects of BN 80933.

In vitro antioxidant neuroprotective activity of BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation.

BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation, prevents in vivo brain ischemic/reperfusion injury. In the present study, BN 80933 was shown to protect neurons from hypoxia-induced cell death in primary cultures of cortical neurons. BN 80933 prevented lactate dehydrogenase activity elevation induced by hypoxia, displaying an IC50 value of 0.15 +/- 0.05 microM. This effect was likely due to the antioxidant properties of BN 80933 because Trolox, but not NG-nitro-L-arginine, also elicited protection. The antioxidant property of BN 80933 was then further investigated on HT-22 cells subjected to buthionine sulfoximine- or glutamate-induced glutathione depletion. The relative order of potency of the various compounds to inhibit oxidative stress-induced neuronal death (BN 80933 > U104067 > butylated hydroxytoluene > 17beta-estradiol > Trolox > vitamin E) correlated with their ability to inhibit brain membrane lipid peroxidation (correlation coefficient = 0.939). BN 80933 afforded protection even when added 6 h after glutamate exposure. BN 80933 did not reverse intracellular glutathione depletion but prevented elevation of the level of beta-epiprostaglandin F2alpha (8-isoprostane), which appeared to be a delayed phenomenon. In conclusion, BN 80933 induces a potent cytoprotection that may be mediated by inhibition of delayed lipid peroxidation.

BN 80933, a dual inhibitor of neuronal nitric oxide synthase and lipid peroxidation: a promising neuroprotective strategy.

Nitric oxide (NO) and reactive oxygen species (ROS) act independently as well as cooperatively to induce neuronal death in acute neurological disorders. Inhibition of neuronal nitric oxide synthase (nNOS) and inhibition of lipid peroxidation induced by ROS have both been proposed as neuroprotective strategies in stroke and trauma. Recently, in our laboratory, the combination of the two strategies was found to be synergistic in reducing neuronal damage. Here, we report that BN 80933 [(S)-N-[4-[4-[(3,4-dihydro-6-hydroxy-2, 5,7, 8-tetramethyl-2H-1-benzopyran-2-yl)carbonyl]-1-piperazinyl]phenyl]-2- thiophenecarboximidamide], a compound that combines potent antioxidant and selective nNOS inhibitory properties in vitro, affords remarkable neuronal protection in vivo. Intravenous administration of BN 80933 significantly reduced brain damage induced by head trauma in mice, global ischemia in gerbils, and transient focal ischemia in rats. Treatment with BN 80933 (0.3-10 mg/kg) significantly reduced infarct volume (>60% protection) and enhanced behavioral recovery in rats subjected to transient (2-h) middle cerebral artery occlusion and 48-h or 7-day reperfusion. Furthermore, treatment with BN 80933 commencing up to 8 h after the onset of ischemia resulted in a significant improvement of neurological outcome. All these results indicate that BN 80933 represents a class of potentially useful therapeutic agents for the treatment of stroke or trauma and possibly neurodegenerative disorders that involve both NO and ROS.

Nitric oxide synthases: targets for therapeutic strategies in neurological diseases.

Glutamate excitotoxicity, oxidative stress, and mitochondrial dysfunctions are common features leading to neuronal death in cerebral ischemia, traumatic brain injury, Parkinson's disease, Huntington's disease, Alzheimer's disease and amyotrophic lateral sclerosis. Nitric oxide (NO) alone or in cooperation with superoxide anion and peroxynitrite is emerging as a predominant effector of neurodegeneration The use of NO synthase (NOS) inhibitors and mutant mice lacking each NOS isoform have provided evidence for the injurious effects of NO derived from neuronal or inducible isoforms. New neuroprotective strategies have been proposed with selective NOS inhibitors for the neuronal (ARL17477) or the inducible (1400 W) isoforms or with compounds combining in one molecule selective nNOS inhibition and antioxidant properties (BN 80933), in experimental ischemia-induced acute neuronal damage. The efficacy of these new strategies is well established in acute neuronal injury but remains to be determined in more chronic neurological diseases.

Differential effects of tyrosine kinase inhibitors on contraction and relaxation of the aortas of normotensive and hypertensive rats.

The contribution of tyrosine kinase activity to vasoreactivity in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats was investigated on isolated aortic preparations by the use of two tyrosine kinase inhibitors: methyl-2,5-dihydroxycinnamate (30 microM) and genistein (30 microM). The pretreatment of endothelium denuded aorta with methyl-2,5-dihydroxycinnamate reduced the sensitivity of the rings to noradrenaline to a larger extent in SHR than in WKY. The relaxing effects evoked by methyl-2,5-dihydroxycinnamate and genistein on the sustained contraction induced by endothelin-1 were also more pronounced in SHR denuded rings. Furthermore, in presence of methyl-2,5-dihydroxycinnamate, the endothelium-independent contractile responses to equipotent doses of cyclopiazonic acid were more depressed in SHR than in WKY. In WKY and SHR endothelium-intact aortas contracted with either phenylephrine or endothelin-1, carbachol and cyclopiazonic acid evoked endothelium derived relaxing factor (EDRF)/nitric oxide (NO)-dependent relaxations which were reduced by pretreatment of the rings with methyl-2,5-dihydroxycinnamate or genistein. These inhibitory effects were larger in WKY rings and more important on the cyclopiazonic acid response. In addition, sodium orthovanadate (30 microM) potentiated the noradrenaline-mediated contractions of endothelium-denuded SHR rings and reduced the cyclopiazonic acid-induced relaxation of endothelium-intact WKY rings. The present study suggests a regulatory role for tyrosine kinase in the smooth muscle contraction and the endothelium-dependent relaxation in WKY and SHR aortas and demonstrates the existence of a different relationship in the effect of tyrosine kinase inhibitors on vasoreactivity between SHR and WKY. We propose that an increase in the tyrosine kinase activity in SHR could lead to an enhanced reactivity of Ca2+-linked contractile mechanisms. In addition, our results suggest a link between the loss of tyrosine kinase activity and the altered endothelium-dependent relaxation associated with hypertension.

Synergistic protective effects of antioxidant and nitric oxide synthase inhibitor in transient focal ischemia.

Both nitric oxide synthase (NOS) inhibitors and free radical scavengers have been shown to protect brain tissue in ischemia-reperfusion injury. Nitric oxide and superoxide anion act via distinct mechanisms and react together to form the highly deleterious peroxynitrite. Therefore the authors examined the effects and the interaction between the NOS inhibitor, NG nitro-L-arginine (LNA) and the antioxidant/superoxide scavenger, di-tert-butyl-hydroxybenzoic acid (DtBHB) in the rat submitted to 2 hours of middle cerebral artery occlusion. Posttreatment was initiated 4 hours after the onset of ischemia and infarct volume was measured at 48 hours. The dose-related effect of LNA resulted in a bell-shaped curve: 15, 56, 65, and 33% reduction of total infarct for 0.03, 0.1, 0.3, and 1 mg/kg (intravenously [IV]) respectively and 11% increase in infarct volume for 3 mg/kg (IV). Whereas DtBHB (20 mg/kg; intraperitoneally [IP]) was ineffective, the dose of 60 mg/kg produced 65% protection in infarct volume. The combination of a subthreshold dose of LNA (0.03 mg/kg; IV) and DtBHB (20 mg/kg; IP) resulted in significant reduction (49%) in infarct volume. These results show that LNA and DtBHB act synergistically to provide a consistent neuroprotection against ischemic injury when administered 4 hours after ischemia. This suggests that nitric oxide and free radicals are involved and interact in synergy in ischemia-reperfusion injury.

Endothelin receptors in testosterone-induced prostatic hypertrophy in rats.

Endothelin receptors were characterized in rat prostate and potential modification of these receptors was investigated in prostatic hypertrophy induced by testosterone. Both ET(A) and ET(B) endothelin receptor mRNA were detected in rat prostate, whereas binding experiments show the presence of only ET(A) receptors. Testosterone administration produced a 75% increase in prostate weight. Although the density of prostatic endothelin receptors was decreased from 348 +/- 75.0 fmol/mg protein in control rats to 252 +/- 39.9 fmol/mg protein in testosterone-treated animals, the total amount of receptors per prostate was unchanged. The steady-state level of ET(A)- and ET(B)-receptor mRNA was not altered by testosterone treatment. These results suggest that endothelin receptors are not affected in prostatic hypertrophy induced by testosterone.

Comparison between endothelial and neuronal nitric oxide pathways in rat aorta and gastric fundus.

This study examines the ability of different nitric oxide synthase (NOS) inhibitors and NO donors to inhibit the endothelium-dependent relaxation of the rat aorta and the NANC relaxation of the rat gastric fundus. NG-Nitro-L-arginine, N-monomethyl-L-arginine, and S-methyl-L-thiocitrulline elicite comparable potency in the aorta and in the fundus. However, 1-(2-trifluoromethyl)imidazole (TRIM), unlike 7-nitroindazole, is more potent on the fundus than on the aorta, showing that TRIM elicits a selective functional inhibition of the neural NOS isoform. (1H)-(1,2,4)Oxadiazole(4,3-a)quinoxalin-1-one, a selective inhibitor of soluble guanylyl cyclase, inhibits the dilator response in both tissues and the cyclic GMP mimetic, 8-Br-cGMP, is 16 times more potent for inducing relaxation in the gastric fundus than in the aorta. However, methylene blue and LY-83583, two other inhibitors of soluble guanylyl cyclase and superoxide anion-generating agents, are at least 100 times less potent on fundus strips than on aortic rings. The data suggest that once released into the extracellular space, NO is more susceptible to inactivation by superoxide anions in the vascular tissue than in the gastric fundus. Thus, the study shows that selective inhibition of NO in a target tissue may be reached not only at the NOS isoform level but also by the manipulation of the NO pathway.

Effects of ANF infusion on the renal responses to lower-body negative pressure in humans.

To investigate the role of atrial natriuretic factor (ANF) in renal responses to a decrease in central blood volume, we examined the effects of ANF infusion on renal function and hormones during prolonged lower-body negative pressure (LBNP). Ten healthy volunteers participated in two experimental sequences, each comprising a 120-min baseline period followed by the application of -20 mm Hg LBNP for 90 min. During one of the two sequences, ANF was infused throughout LBNP application at the constant rate of 2.5 ng/kg/min. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by using inulin and p-aminohippuric acid clearance techniques. LBNP induced a significant decrease in ERPF (534 +/- 28 to 457 +/- 26 ml/min; p < 0.05), GFR (120 +/- 2.5 to 112 +/- 2.5 ml/min; p < or = 0.01), in urine excretion (12 +/- 0.9 to 5.6 +/- 0.5 ml/min; p < 0.001), in sodium excretion (0.36 +/- 0.03 to 0.30 +/- 0.02 mmol/min; p < 0.05), and in plasma ANF (19 +/- 3 to 11 +/- 2 pg/ml; p = 0.001) concomitant with an increase in plasma renin activity (PRA; 0.48 +/- 0.09 to 0.87 +/- 0.16 ng/ml/h; p = 0.01) and of forearm vascular resistance (FVR; p < 0.05). The combination of ANF infusion with LBNP led to a slight increase in plasma ANF from baseline (from 20 +/- 2 to 28 +/- 3 pg/ml; p < 0.05). Compared with values obtained during LBNP with saline vehicle infusion, values obtained during LBNP with ANF infusion were similar for ERPF (463 +/- 23 vs. 457 +/- 26 ml/min), for GFR (111 +/- 2 vs. 112 +/- 2 ml/min), and for urine excretion (7 +/- 0.6 vs. 5.6 +/- 0.5 ml/min; p = 0.07), but greater for fractional excretion of sodium (2.38 +/- 0.25% vs. 1.91 +/- 0.11%; p < 0.05) and FVR (p < 0.05), and smaller for PRA (0.49 +/- 0.1 vs. 0.87 +/- 0.16 ng/ml/h; p < 0.01). These data show that ANF infusion attenuates the antinatriuretic effect of low-level LBNP and its PRA-increasing effects without altering renal hemodynamic responses to LBNP, although there is a decrease in the LBNP-induced forearm vasoconstriction. These results were obtained with plasma ANF levels slightly higher than those in baseline. They support the hypothesis that a decrease in ANF secretion might contribute to the antinatriuretic effect of LBNP.

Augmented endothelium-dependent contraction to angiotensin II in the SHR aorta: role of an inducible cyclooxygenase metabolite.

The purpose of this study was to investigate the mechanisms involved in the angiotensin II-induced increase in the contractile response of the hypertensive wall after prolonged incubation in the organ-bath buffer. In 5-h incubated rings, the contractile response to angiotensin II in aortic rings with endothelium from spontaneously hypertensive rats (SHRs) was markedly exaggerated in comparison to 2-h incubated rings. No such potentiation was observed in SHR rings after removal of the endothelium or in intact and denuded Wistar-Kyoto (WKY) rat rings. Aspirin and SQ29548 inhibited and cycloheximide and actinomycin D reduced the time-dependent enhanced response to angiotensin II in rings with endothelium from SHRs. In SHR rings with endothelium incubated for 2 h, the contractions caused by angiotensin II were potently inhibited by piroxicam but were unaffected by NS-398. Conversely, in rings incubated for 5 h, the hyperresponsiveness to angiotensin II was inhibited to a greater extent by NS-398 than by piroxicam. Piroxicam but not NS-398 had a further inhibitory effect on the residual angiotensin II-induced contraction in actinomycin D-treated rings incubated for 5 h. In conclusion, our study shows that long-term incubation leads to hyperresponsiveness to angiotensin II in SHR aorta with endothelium. The enhanced response is associated with the induced release of vasoconstrictor prostanoids sensitive to the inhibitory effect of NS-398, a preferential inhibitor of COX-2.

Alpha1-adrenoceptors in testosterone-induced prostatic hypertrophy.

Modifications of rat prostatic alpha1-adrenoceptors were investigated in testosterone-induced prostatic hypertrophy. [3H]prazosin bound to a single class of binding sites with a dissociation constant of 57.9+/-5.02 pM. The greater part of the binding capacity (24.6+/-1.02 fmol/mg protein) was made up of chloroethylclonidine-resistant binding sites that showed high-affinity for oxymetazoline and 5-methyl-urapidil, and was identified as alpha1A-adrenoceptors. The remaining chloroethylclonidine-sensitive binding sites that showed low-affinity for oxymetazoline and 5-methyl-urapidil were preferentially identified as alpha1B-adrenoceptors. mRNA for the three alpha1-adrenoceptors (alpha1a, alpha1b and alpha1d) was detected. Testosterone administration produced a 23% decrease of alpha1-adrenoceptor density, likely by an increase of prostatic glandular epithelium and a decrease in the relative proportion of smooth muscle, thus of alpha1-adrenoceptor density. The steady state level of mRNAs for alpha1-adrenoceptors was not modified by testosterone treatment. These results indicate that prostate alpha1-adrenoceptors are not affected in the prostatic hypertrophy induced by testosterone.

Renal and vascular effects of C-type and atrial natriuretic peptides in humans.

C-type natriuretic peptide (CNP) may affect renal and vascular functions differently from atrial natriuretic peptide (ANP). The objective of this study was to compare the renal and vascular actions of CNP to those of ANP in normal men. CNP or ANP (0.005, 0.01, and 0.05 microg x kg(-1) x min(-1)) were given by infusion to eight healthy volunteers. CNP caused dose-dependent increases in natriuresis (U(Na)) and in the fractional excretion of sodium (FE(Na)) with no effect on diuresis (UV), renal plasma flow, and glomerular filtration rate (GFR). Fraction of filtration (FF) increased only with the 0.05 microg x kg(-1) x min(-1) CNP dose. ANP caused larger increases in U(Na), FE(Na), and FF than CNP and also increased UV at 0.01 and 0.05 microg x kg(-1) x min(-1) and GFR at 0.05 microg x kg(-1) x min(-1). Although the ANP and CNP infusions produced similar elevation in the respective peptides plasma levels, urinary and nephrogenous guanosine 3',5'-cyclic monophosphate increased less in response to CNP than to ANP. Blood pressure, forearm blood flow, plasma renin activity, and aldosterone remained unaffected during the peptides infusion. Plasma ANP increased slightly during CNP infusion. Our data indicate a higher threshold of renal response to CNP than to ANP. In contrast to ANP, CNP probably may not act as an endocrine factor in humans.

Pharmacological evidence that different alpha 1 adrenoceptor subtypes mediate contraction in rabbit prostate and hypogastric artery.

The alpha 1 adrenoceptor subtypes mediating contraction of rabbit prostate and hypogastric artery were pharmacologically characterized using an isolated organ bath technique. The prostate had the same sensitivity to the contractile action of methoxamine and phenylephrine, whereas the hypogastric artery was five times less sensitive to the action of methoxamine in comparison with phenylephrine. Clonidine elicited contraction in the hypogastric artery but not in the prostate. BMY7378 was about 70-fold more potent to antagonize the phenylephrine-induced contraction in the hypogastric artery (pA2 8.14) than in the prostate (pA2 6.28), and 5-methyl-urapidil was about three-fold more potent on prostrate than on hypogastric artery. The potency of different alpha 1-adrenoceptor antagonists tested in the rabbit prostate was significantly correlated with their binding affinity for the expressed recombinant alpha 1A-, but not alpha 1B- or alpha 1D-, adrenoceptor subtype, whereas, the potency of the alpha 1-adrenoceptor antagonists tested in the rabbit hypogastric artery was better correlated with the defined alpha 1D-adrenoceptor. Chloroethylclonidine produced a 10-fold rightward shift in the phenylephrine concentration-response curve in the hypogastric artery but only had a weak effect in the prostate. The results indicate that significant heterogeneity exists among alpha1-adrenoceptor in the rabbit hypogastric artery (alpha 1D-adrenoceptor) and the prostate (alpha 1A-adrenoceptor).

Effects of angiotensin I and angiotensin II in blood vessels: greater influence of converting enzyme activity in the rabbit basilar artery.

We investigated the constrictor effects of Angiotensin I (Ang I) and Angiotensin II (Ang II) on rabbit peripheral (aorta, carotid artery, mesenteric artery, saphenous artery) and cerebral (basilar artery) vessels and in rat aorta in functional organ bath studies. The effect of angiotensin converting enzyme (ACE) inhibition by captopril was also assessed in these preparations. Ang II elicited concentration-dependent contractions with comparable potency in rabbit and rat endothelium-free vascular rings (pD2 about 8.5) which indicates a lack of species and regional variation in the contractile responses to Ang II. The responses to Ang II were reduced by the presence of a functional endothelium in rabbit mesenteric artery and in rat aorta. Since ACE determines the plasma and tissue conversion of Ang I to active Ang II, we calculated the ratio R (EC50 Ang I-induced contraction: EC50 Ang II-induced contraction) as an indicator of the tissue ACE effectiveness. In the aorta without endothelium, Ang I was found to be much less potent than Ang II in the rabbit (R = 44) compared with the rat (R = 3.5). This species difference in the aortic conversion of Ang I to Ang II was confirmed by the use of captopril. Captopril (10(-6) M) shifted the Ang I concentration/ response curve by 2- and 14-fold to the right in rabbit and rat respectively. In other rabbit blood vessels, the rank order of potency to Ang I in endothelium denuded rings was basilar artery > > carotid artery > or = aorta > or = saphenous artery. In addition, the R value was the lowest for the basilar artery (R = 2.5). This is in agreement with the highest rightward shift (78-fold) of the Ang I concentration/response curve by captopril for basilar artery in comparison with only 3-, 8- and 3-fold shifts observed in carotid artery, saphenous artery and aorta respectively. In conclusion, our data provide evidence for a greater influence of ACE in rabbit basilar artery than in peripheral vessels.

Pharmacological characterization of alpha 1-adrenoceptor subtype mediating regulation of arterial pressure and urethral perfusion pressure in the anaesthetized rat.

1. The alpha 1-adrenoceptor subtypes mediating the regulation of arterial pressure (AP) and urethral perfusion pressure (UP) in the anaesthetized rat were characterized by using selective alpha 1-adrenoceptor agonists and antagonists. 2. Intravenous administration of selective alpha 1-adrenoceptor agonists elicited a dose-dependent increase in AP and UP. The rank order of agonist potency: oxymetazoline (ED50, 6.2 and 8.2 nmol kg-1 > phenylephrine (ED50, 32 and 27 nmol kg-1 > methoxamine (ED50, 300 and 296 nmol kg-1 was the same for AP and UP, respectively. 3. The effects of phenylephrine on AP and UP were antagonized, in a dose related-manner, by pretreatment with alfuzosin, BMY 7378, 5-methyl-urapidil, phentolamine, prazosin, spiperone and WB 4101.5-methyl-urapidil was the only alpha 1-adrenoceptor antagonist more potent on UP than on AP. 4. The potency of the different alpha 1-adrenoceptor antagonists tested on AP and UP was significantly correlated with their binding affinity for the expressed recombinant alpha 1a-, but not alpha 1b- or alpha 1d-, adrenoceptor subtype. 5. The results suggest that in the anaesthetized rat (1) both AP and UP are regulated by the alpha 1A-adrenoceptor subtype; and (2) the urogenital selectivity of 5-methyl-urapidil may be due to the existence of multiple forms of the alpha 1A-adrenoceptor.

Growth factors and vascular wall.

The reactivity and the structure as well as the growth of the vascular wall depend on a variety of locally synthetised factors in a process of a permanent structure-function adaptation. These substances exert their inhibitory or stimulatory growth effects by paracrine or autocrine mechanisms. These factors command the reorganisation of the structure of existing blood vessel or the creation of new vessels. They are synthetised and secreted form either endothelial and smooth muscle cells or circulating cells (in particular macrophages, platelets). The growth factors are multiple and interactive insuring a role of physiological vascular modeling in normal conditions but they may participate and even induce dramatic structural dysfunctions that are observed in pathologies such as venous diseases, atherosclerosis or hypertension. Among them, the polypeptides PDGF (platelet derived growth factor), FGF (fibroblast growth factor) and TGF beta (transforming growth factor beta) play a major role. Other factors like cytokines, IGFs (insulin like growth factors), PAF (platelet activating factor) endothelins or nitric oxide have also to be considered. Thus, the vascular wall structure is under the influence of a complex group of growth factors which become to be identified and may be the targets of new therapies of the vessels.

Decrease in endothelin-1 renal receptors during the 1st month of life in the rat.

Endothelin-1 (Et1), like angiotensin II, is implicated in postnatal maturation and development. The present study was designed to identify Et1 receptors and subtype Et1 receptors present in rat kidney between 1 and 30 days of postnatal life. On day 1, high-affinity and high-density Et1 binding sites were identified in rat kidney. The dissociation constant and maximum binding for ET1 to membranes from whole kidney were 0.073 +/- 0.05 nM and 1,345.9 +/- 73 fmol/mg protein, respectively. On day 30, affinity and receptor density were markedly decreased. The dissociation constant and maximum binding were 0.147 +/- 0.021 nM (P < 0.01) and 633.2 +/- 56.4 fmol/mg protein (P < 0.001), respectively. Using BQ 123 (EtA-selective antagonist) and sarafotoxin S6c (EtB-selective agonist), the two Et1 receptor subtypes EtA and EtB were identified in 1- and 30-day-old rat kidney. BQ 123 selectively recognized EtA receptors with high affinity (2.9 +/- 0.44 on day 1 and 4.0 +/- 0.5 nM on day 30) and sarafotoxin S6c bound with higher affinity EtB receptors (0.871 +/- 0.14 on day 1 and 0.717 +/- 0.12 nM on day 30). Between birth and day 30, the EtA binding capacity was decreased (304 +/- 27 vs. 752 +/- 202 fmol/mg protein, P < 0.05), whereas EtB binding was not affected (514 +/- 87 vs. 656 +/- 171 fmol/mg protein, NS). The decrease in the total number of Et1 receptors during the 1st month of life may be due to the concomitant decrease in the number of EtA receptors. Increased Et1 receptor density in early postnatal life suggests an influence of Et1 on immature kidney circulation and/or kidney growth.