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M V Conde

Publications and source records attributed to M V Conde.

At least 19 recordsLinked to original sources
PubMed2000

Regulation of beta-adrenoceptor-mediated relaxation of the rat aorta is modulated by endogenous ovarian hormones.

The aim of this study was to assess the influence of the endogenous status of ovarian hormones on the relaxation induced by the beta-adrenoceptor agonists isoprenaline (isoproterenol) and dobutamine in thoracic aorta segments, precontracted with noradrenaline, from age-matched (13-week-old) virgin (oestrus) and ovariectomized (OVX) prepubertal female Wistar rats. Isoprenaline-induced relaxation was decreased in intact aortic segments from OVX rats compared with that in segments from oestrus rats. Relaxation was significantly reduced by endothelium removal, 1 micromol/l propranolol or 100 micromol/l N(G)-nitro-L-arginine methyl ester (L-NAME). The beta(1)-adrenoceptor agonist dobutamine induced less relaxation in intact arteries from oestrus rats than did isoprenaline, and dobutamine-induced relaxation was markedly less in intact segments from OVX compared with oestrus rats. This dobutamine-induced relaxation was abolished by endothelium removal, and reduced by 1 micromol/l propranolol, 100 micromol/l L-NAME or 1 micromol/l yohimbine. Cholera toxin (an activator of the stimulatory G-protein G(s)) caused relaxation in intact arteries from oestrus rats; this relaxation was decreased by both deprivation of ovarian hormones and endothelium removal. Forskolin (a direct activator of the catalytic subunit of adenylate cyclase) and sodium nitroprusside (a nitric oxide donor and cGMP-dependent vasodilator agonist) induced similar endothelium-independent relaxation in arteries from both oestrus and OVX rats. These results suggest that the relaxation elicited by endothelial beta-adrenoceptor activation in the rat thoracic aorta is impaired by deprivation of female ovarian hormones; this impairment is caused, at least in part, by decreases in both the endothelial release of NO and G(s) function.

Adrenergic beta-Agonists↗
PubMed1999

Superoxide anion and K+ channels mediate electrical stimulation-induced relaxation in the rat basilar artery.

Electrical field stimulation (a single pulse, 0.2 ms) caused a rapid relaxation of rat basilar artery segments precontracted with different agents, but not with 30 mM KCl. This relaxation was not modified by endothelium removal, 10 microM tetrodotoxin, 1 microM propranolol, 1 microM atropine, 30 microM indomethacin, 10 microM methylene blue, 100 microM N(G)-nitro-L-arginine methyl ester or 1 microM cimetidine but it was significantly reduced by 50 and 100 U/ml superoxide dismutase. Charybdotoxin (0.1 and 0.2 microM), a blocker of large-conductance Ca2+-activated K+ channels (BK(Ca)), decreased the relaxation elicited by electrical stimulation, whereas it was unaltered by 10 microM glibenclamide or 1 microM apamin, blockers of ATP-sensitive (K(ATP)) or small-conductance K(Ca) channels, respectively. Thapsigargin (0.01 and 0.1 microM), an inhibitor of sarcoplasmic reticulum Ca2+-ATPase, increased the electrical stimulation-induced relaxation, which was nearly abolished by charybdotoxin. These results show that electrical stimulation induces endothelium-independent and non-neurogenic relaxations in the rat basilar artery. This response appears to involve generation of superoxide anion, increase of cytosolic free Ca2+ concentration and subsequent activation of BK(Ca) channels.

Acetylcholine↗
PubMed1997

Involvement of protein kinase C in the supersensitivity to 5-HT caused by oxidized low-density lipoproteins.

The effect of native (n-LDL) and oxidized (ox-LDL) low-density lipoproteins and lysophosphatidylcholines (LPCs) on: (1) vasodilator responses induced by acetylcholine (ACh) in intact rabbit aorta segments, and (2) vasoconstrictor responses to serotonin (5-HT), and potassium (K+) in endothelium denuded segments was investigated. In intact vessels, 100 microg/ml ox-LDL did not modify ACh-induced relaxation, while it was diminished by 300 microg/ml ox-LDL and abolished by 50 microM LPCs. In contrast, this relaxation was unaltered by n-LDL (100 or 300 microg/ml). In deendothelialized arteries, 100 and 300 microg/ml n-LDL as well as 50 microM LPCs did not modify the contractions induced by 5-HT or K+, while 100 or 300 microg/ml ox-LDL increased the 5-HT-induced contraction, without altering those induced by 75 mM K+. Incubation with 100 or 300 microg/ml ox-LDL increased the contractile response to the protein kinase C (PKC) activator phorbol 12,13-dibutyrate (PDB) (0.1-1 microM) in a concentration-dependent manner, which was blocked by staurosporine (0.1 microM), and unaltered by (50 microM) calphostin C or (50 microM) chelerythrine, the three are PKC inhibitors. Preincubation with 0.05 microM PDB increased the contraction elicited by 5-HT, while staurosporine decreased the PDB-induced contraction, and prevented the 5-HT response increase caused by 300 microg/ml ox-LDL. These results suggest that only ox-LDL reduces endothelium-dependent relaxation and elicits PKC activation, and that this activation mediates, at least in part, the vasoconstrictor response to 5-HT.

Acetylcholine↗
PubMed1995

Cat cerebral arteries are functionally innervated by serotoninergic fibers from central and peripheral origins.

BACKGROUND AND PURPOSE: Tryptophan hydroxylase activity and responses to tyramine were analyzed in cat cerebral arteries to investigate serotoninergic innervation. METHODS: Enzymatic activity and responses to tyramine were measured in vessels from animals subjected to cervical gangliectomy and dorsal and median raphe nuclei lesions. RESULTS: Tryptophan hydroxylase activity in cat cerebral arteries was reduced after ganglia removal and raphe nuclei destruction. Contractile responses of the middle cerebral artery after gangliectomy were decreased by ketanserine. Dorsal raphe nucleus destruction had a significant effect on the contractile response, whereas median raphe nucleus destruction had only a slight effect. CONCLUSIONS: Cat cerebral arteries receive serotoninergic innervation from central and peripheral origins.

Animals↗
PubMed1994

Different influence of superoxide anions and hydrogen peroxide on endothelial function of isolated cat cerebral and pulmonary arteries.

1. Exogenous superoxide dismutase (SOD) or catalase did not modify isolated cat middle cerebral arterial basal tone. Catalase but not SOD reduced ACh relaxation. 2. H2O2 induced endothelium-independent relaxation which was abolished by catalase. 3. 3-Amino-1,2,4-triazole (AT) evoked endothelium-dependent contractions and diminished ACh relaxation. 4. Diethyldithio carbamic acid (DETC) induced endothelium-independent relaxation and did not modify ACh vasodilatation. 5. ACh relaxation of cat isolated pulmonary arteries was unaffected by SOD, catalase or AT, and diminished by DETC. 6. Endothelial catalase but neither SOD nor superoxide anions is involved in EDRF cerebral vasodilatation and H2O2 participates in ACh relaxation. In pulmonary arteries, only endothelial SOD activity plays a role.

Acetylcholine↗
PubMed1994

Serotonergic activity in rat cerebral arteries depends on dorsal raphe nucleus but not on median raphe nucleus.

The effect of Chlorimipramine and Muscimol on serotonergic activity in rat cerebral arteries and in dorsal and median raphe nuclei were used to study the presence of a serotonergic innervation in the cerebral blood vessels functionally dependent on the brainstem nuclei activity. Serotonergic activity was appraised in rat cerebral arteries from 5-hydroxyindoleacetic acid (5-HIAA) disappearance rate or 5-hydroxytryptophan (5-HTP) accumulation after inhibiting monoamine oxidase (MAO) or aromatic amino acids decarboxylase, respectively. In dorsal and median raphe nuclei the decay with time of 5-HIAA after MAO inhibition was used to estimate serotonergic activity. Chlorimipramine significantly reduced serotonergic activity in cerebral blood vessels and in both raphe nuclei. 5-HIAA basal levels in these blood vessels were not altered by treatment with the drug. Muscimol evoked only a decrease in the serotonergic activity of the median raphe nucleus. These results suggest that rat cerebral arteries receive serotonergic fibers functionally active arising mainly from dorsal raphe nucleus.

5-Hydroxytryptophan↗
PubMed1993

Effects of L-arginine analogues in isolated cat cerebral arteries.

The possible contribution of nitric oxide (NO) to the endothelium-dependent relaxation of isolated cat cerebral arteries was studied by examining the effects of the L-arginine (L-ARG) analogues L-canavanine and NG-nitro-L-arginine (L-NOARG) on acetylcholine-induced relaxation. L-canavanine (100 microM) as well as L-NOARG (10 microM) decreased significantly the relaxant response of acetylcholine, their effect being significantly reversed by L-arginine (10 microM) but not by D-arginine (10 microM). In resting conditions, L-NOARG (10 microM) elicited a contraction of 314 +/- 42 mg in arteries endowed with endothelium that was significantly diminished by endothelium removal to 88 +/- 35 mg, and by (10 microM) L-arginine to 135 +/- 54 mg. L-canavanine (100 microM) induced contractions in arteries with and without endothelial cells which were not statistically different. The results suggest that the endothelium of cat cerebral arteries has the ability to synthesize nitric oxide from L-arginine and to release it, even in the absence of a stimulus such as that of acetylcholine. L-NOARG seems to be a specific and powerful inhibitor of nitric oxide synthesis.

Acetylcholine↗
PubMed1991

Lesion of the dorsal raphe nucleus induces supersensitivity to serotonin in isolated cat middle cerebral artery.

Simultaneous lesions of dorsal and median raphe nuclei were induced after 15 days postjunctional supersensitivity to serotonin in isolated segments of cat middle cerebral artery. The same result was obtained when only the dorsal raphe nucleus was destroyed. The lesion of the median raphe nucleus brought about an increased contractile response to serotonin only at the three first doses used. The contractile response to noradrenaline was unaffected by these treatments. These results suggest the existence of a serotonergic innervation of the cat middle cerebral artery whose main origin might be the dorsal raphe nucleus.

Acetylcholine↗
PubMed1991

Response of isolated cat middle cerebral artery to platelets: effect of endothelium removal.

1. Platelets induced an endothelium-independent contraction in isolated cat middle cerebral artery under resting conditions. In precontracted segments they evoked an endothelium-dependent contraction followed by a relaxation. 2. The contraction induced by serotonin was unaffected by endothelium removal either in the absence or in the presence of a previous tone. 3. The contractile response to platelets and serotonin under resting tension was blocked in the same way by ketanserin, methysergide or cyproheptadine. 4. After adding the platelets, serotonin could be measured in the bath medium. 5. These results suggest that the endothelium plays a minor role in the contraction induced by platelets, which is partly due to serotonin release.

Animals↗
PubMed1991

Different influence of endothelium in the mechanical responses of human and cat isolated cerebral arteries to several agents.

The present work was undertaken to elucidate the role of the vascular endothelium in the changes of isometric tension elicited by different compounds in isolated cylinders of human and cat cerebral arteries and cat pulmonary arteries. Endothelium removal by rubbing significantly reduced the relaxing response to acetylcholine (ACh) of isolated segments of all the arteries. The same treatment did not modify the contraction elicited by 5-hydroxytryptamine (5-HT) in the human and cat cerebral segments but increased the contractile effect of the amine in cat pulmonary arteries. The mechanical responses to vasopressin, ATP and adenosine in isolated segments of cat cerebral arteries were unaffected after removing the endothelial layer. L-Arginine, but not D-arginine (10(-5) M), enhanced significantly the relaxation induced by increasing doses of ACh in unrubbed cat cerebral arteries whereas it did not modify the response to ACh in rubbed ones. However, L-arginine had no effect on the dose-response curve to 5-HT in both kinds of preparation and did not change the tone in precontracted unrubbed cat cerebral segments. These results suggest that the endothelium of the cerebrovascular bed plays a minor role in regulating the mechanical response induced by several vasoactive agents, although it retains its ability to produce an endothelium-derived relaxing factor.

Acetylcholine↗
PubMed1987

In vitro studies of the carotid rete mirabile of Artiodactyla.

The carotid rete of Artiodactyla, an intracranial arterial plexus which supplies blood to the brain, has intrigued investigators for a long time. This study was designed to examine the responsiveness of isolated retial arteries (250-700 microns in external diameter) of goat, pig, and cattle. The findings in these arteries were compared to those observed in cerebral arteries (250-650 microns in external diameter) of the same animal species. The magnitude of the arterial responses to potassium chloride varied with the resting tension applied to the tissue. The two types of vessels exhibited similar resting tension values (0.3 g) for maximal tension development in response to potassium chloride; however, the ability of retial vessels to contract in the presence of potassium chloride was consistently smaller than that of cerebral arteries. The contractile response of retial arteries to norepinephrine (10(-9) to 10(-4) M), tyramine (10(-8) to 10(-3) M), and field electrical stimulation (2-16 Hz) was negligible. The same retial arteries exhibited dose-dependent contractions in response to 5-hydroxytryptamine (10(-9) to 10(-5) M) and histamine (10(-9) to 3 X 10(-4) M). Cerebral arteries exhibited larger responses to the vasoactive agents than retial arteries. Our findings indicate that retial arteries have a small vasomotor activity in response to adrenergic stimulation or to vasoactive agents. Therefore, the carotid rete of Artiodactyla may have a low ability to change resistance to blood flow under neural or hormonal influences.

Animals↗
PubMed1984

Indirect adrenergic effect of histamine in human cerebral arteries: influence of post-mortem period.

Histamine (10(-4) M) increased the radioactivity released from human cerebral arteries obtained within 6 h of death and preincubated with [3H]noradrenaline. In the presence of 10(-6) M cocaine or if 7 or more hours had elapsed since death, 10(-4) M histamine was unable to change basal levels of tritium outflow. The radioactivity retained by the tissue was higher when cerebral blood vessels were obtained within a post-mortem period of 6 h. These results suggest that histamine may release noradrenaline from the sympathetic innervation of human cerebral arteries and that the function of this innervation lasts only 6 h after death.

Adult↗
PubMed1984

Evidence for the direct effect of vasopressin on human and goat cerebral arteries.

The effects of vasopressin on the cerebral circulation were studied in conscious goats and in isolated human and goat cerebral arteries. Infusion of 1 to 12 mU of vasopressin into the internal maxillary artery of unanesthetized goats caused dose-dependent reductions in cerebral blood flow, a decrease of 36 +/- 4.7% (mean +/- S.E.) occurring with the highest dose. Cumulative application of vasopressin (10(-12) to 10(-6) M) markedly constricted human and goat cerebral arteries in vitro, the effect being more prominent in human vessels. (1-Deaminopenicillamine, 4-valine)-8-D-arginine-vasopressin, a competitive antagonist of the pressor effects of vasopressin, partially inhibited the cerebral vasoconstriction produced by vasopressin in vivo and in vitro without affecting the vasoconstrictor responses to norepinephrine, 5-hydroxytryptamine and potassium chloride. The results indicate that low concentrations of vasopressin produce constriction of cerebral vessels by direct excitatory effects on specific receptor sites. This effect should be considered in certain pathophysiological states in which vasopressin is released in amounts that could interfere with the proper blood supply to the brain.

Animals↗
PubMed1983

Rete mirabile of goat: in vitro effects of adrenergic stimulation.

The carotid rete of the goat, a network of small arteries, is placed in the pathway of the main arteries which supply the brain. This structure lies within the cavernous sinus on each side of the pituitary. The presence of a carotid rete in many mammals has led to frequent speculations about its physiological function. The present study was designed to examine comparatively the responsiveness of goat retial and cerebral arteries to direct or indirect adrenergic stimulation. The contractile response of isolated retial arteries (150-500 micron in external diameter) to norepinephrine (10(-8) - 10(-4)M), field electrical stimulation (2-16 c/s), and tyramine (10(-6) - 10(-3) M) was negligible. In contrast, cerebral arteries of 300-500 micron in external diameter exhibited dose- or frequency-dependent contractions qualitatively similar to those previously described in larger cerebral arteries. The norepinephrine content in the walls of retial arteries was about 13% of that measured in cerebral arteries. These results suggest that the role of the carotid rete in the regulation of resistance to blood flow during adrenergic stimulation is negligible or nonexistent.

Adrenergic Fibers↗
PubMed1983

Neurogenic vasoconstriction of cat cerebral and femoral arteries.

1. Segments of cat posterior communicating artery and femoral artery submitted to field electrical stimulation showed frequency-dependent contractile responses which were decreased by tetrodotoxin, bretylium, and reserpine pretreatment. Phentolamine could only reduce the response of femoral artery segments. Superior cervical gangliectomy also decreased the contractions of cerebral cylinders. 2. The tritium released by electrical stimulation from both kinds of vessels preloaded with [3H]noradrenaline appeared reduced in the presence of tetrodotoxin, bretylium, and after reserpine pretreatment. It was also decreased in cerebral segments after superior cervical gangliectomy. 3. These results suggest that the electrical field stimulates the sympathetic nerve endings of these vessels.

Animals↗
PubMed1981

Relaxation of isolated middle cerebral artery induced by diazoxide.

The effect of diazoxide on isometric tension of goat middle cerebral arteries was investigated both under resting conditions and under contraction produced by 10(-6) M serotonin. In addition, the inhibitory action of diazoxide was tested against contractile effects induced by different experimental interventions such as electrical field stimulation, norepinephrine, tyramine, histamine, and KCl. Diazoxide caused dose-dependent relaxation of cerebral arteries which was more pronounced when the vessels were previously contracted. High doses of diazoxide (10(-3) M) inhibited significantly the contraction induced by electrical field stimulation and all the vasoactive agents used. This inhibitory effect of diazoxide was greater for those drugs that directly or indirectly act through alpha-adrenergic receptor stimulation. Tritium release induced by electrical field stimulation of cerebral arteries previously labelled with 3H-norepinephrine was not affected in the presence of diazoxide. We conclude that diazoxide has a dilatory effect on goat brain vessels due to direct relaxation of smooth muscle together with a possible blockade of the alpha -adrenergic receptors. This effect might explain the maintenance of cerebral blood flow observed in vivo during diazoxide-induced arterial hypotension.

Animals↗