Cáncer de mama metaplásico: a propósito de un caso / Metaplastic breast cancer: A case report

Introducción: El carcinoma metaplásico de mama (CMM) es un tipo raro y agresivo de cáncer de mama que suele diagnosticarse en etapas avanzadas, con tumores de gran tamaño y grado histológico elevado. En este estudio, presentamos un caso de CMM, y realizamos una revisión y discusión de la literatura relacionada. Principales síntomas o hallazgos clínicos: Paciente de 35 años, sin antecedentes personales ni familiares relevantes, que consulta por tumoración mamaria de 2cm, de crecimiento progresivo, que agrega en la evolución umbilicación del pezón y dolor mamario. Se realiza ecografía mamaria que evidencia masa sólida polilobulada con características sospechosas. En suma: masa en mama izquierda BI-RADS 5. Diagnósticos principales, intervenciones terapéuticas y resultados: Se realiza core biopsia y la anatomía patológica evidencia un carcinoma ductal infiltrante, variedad metaplásico, triple negativo y con expresión PDL1>1%. Se realiza mastectomía radical modificada. En la evolución se diagnostica un secundarismo pulmonar, y la paciente recibió tratamiento sistémico de primera y segunda línea. Conclusiones: Dada la naturaleza agresiva de este tipo de tumor, y las limitadas opciones de tratamiento disponibles, la participación en ensayos clínicos puede considerarse para mejorar los resultados en estas pacientes. Un enfoque multidisciplinario, y la revisión en un comité de tumores son fundamentales para guiar las decisiones terapéuticas y proporcionar la mejor atención posible a estas pacientes(AU)

Introduction: Metaplastic breast carcinoma (MBC) is a rare and aggressive type of breast cancer that is often diagnosed in advanced stages, with large tumors and a high histological grade. In this study, we present a case of MBC, and conduct a review and discussion of the related literature. Main symptoms or clinical findings: A 35-year-old patient with no relevant personal or family history presents with a progressively growing 2 cm breast mass, which, over time, develops into nipple retraction and breast pain. A breast ultrasound reveals a suspicious-looking polilobulated solid mass. In summary: a BI-RADS 5 mass in the left breast. Main diagnoses, therapeutic interventions, and outcomes: A core biopsy is performed, and the pathology report reveals an infiltrating ductal carcinoma, metaplastic variety, triple-negative with PDL1 expression > 1%. A modified radical mastectomy is performed. During follow-up, pulmonary metastasis is diagnosed, and the patient receives first and second-line systemic treatment. Conclusions: Given the aggressive nature of this type of tumor and the limited treatment options available, participation in clinical trials may be considered to improve outcomes in these patients. A multidisciplinary approach, and review in a tumor committee are essential to guide therapeutic decisions and provide the best possible care for these patients.(AU)

The suprachiasmatic nucleus is part of a neural feedback circuit adapting blood pressure response.

The suprachiasmatic nucleus (SCN) is typically considered our autonomous clock synchronizing behavior with physiological parameters such as blood pressure (BP), just transmitting time independent of physiology. Yet several studies show that the SCN is involved in the etiology of hypertension. Here, we demonstrate that the SCN is incorporated in a neuronal feedback circuit arising from the nucleus tractus solitarius (NTS), modulating cardiovascular reactivity. Tracer injections into the SCN of male Wistar rats revealed retrogradely filled neurons in the caudal NTS, where BP information is integrated. These NTS projections to the SCN were shown to be glutamatergic and to terminate in the ventrolateral part of the SCN where light information also enters. BP elevations not only induced increased neuronal activity as measured by c-Fos in the NTS but also in the SCN. Lesioning the caudal NTS prevented this activation. The increase of SCN neuronal activity by hypertensive stimuli suggested involvement of the SCN in counteracting BP elevations. Examining this possibility we observed that elevation of BP, induced by α1-agonist infusion, was more than twice the magnitude in SCN-lesioned animals as compared to in controls, indicating indeed an active involvement of the SCN in short-term BP regulation. We propose that the SCN receives BP information directly from the NTS enabling it to react to hemodynamic perturbations, suggesting the SCN to be part of a homeostatic circuit adapting BP response. We discuss how these findings could explain why lifestyle conditions violating signals of the biological clock may, in the long-term, result in cardiovascular disease.

Evidence that some imidazoline derivatives inhibit peripherally the vasopressor sympathetic outflow in pithed rats.

Imidazoline derivatives (e.g. clonidine and moxonidine) and alpha(2)-adrenoceptor agonists (e.g. B-HT 933) have been shown to inhibit sympathetically-induced [(3)H]noradrenaline release in several isolated blood vessels. The present study has compared the potential capability of agonists at imidazoline I(1/2) receptors and/or alpha(1/2)-adrenoceptors to inhibit the sympathetically-induced vasopressor responses in pithed rats. For this purpose, male Wistar rats were pithed and prepared for measurement of diastolic blood pressure and heart rate. Then, the vasopressor responses induced by either selective electrical stimulation (2 ms, 60 V; 0.03, 0.1, 0.3, 1 and 3 Hz) of the vascular sympathetic outflow (T(7)-T(9)) or i.v. bolus injections of exogenous noradrenaline (0.03, 0.1, 0.3, 1 and 3 microg/kg) were determined before and during i.v. continuous infusions of the agonists B-HT 933 (alpha(2)), clonidine (alpha(2), I(1)), moxonidine (alpha(2), I(1)), cirazoline (alpha(1), I(2)), agmatine (putative endogenous ligand of imidazoline receptors) and methoxamine (alpha(1)), or equivalent volumes of physiological saline. Electrical sympathetic stimulation elicited frequency-dependent vasopressor responses which were significantly inhibited during the continuous infusions of B-HT 933, clonidine, moxonidine, cirazoline and agmatine, but not of physiological saline. Interestingly, the vasopressor responses to exogenous noradrenaline, which remained unaffected during the infusions of physiological saline, B-HT 933, moxonidine, cirazoline and agmatine, were significantly blocked during the infusions of clonidine or methoxamine. These results suggest that B-HT 933, moxonidine, cirazoline and agmatine induced a prejunctional inhibition of the vasopressor sympathetic outflow in pithed rats, whilst clonidine inhibited the vasopressor sympathetic outflow by both prejunctional and postjunctional mechanisms.

Pharmacological profile of the clonidine-induced inhibition of vasodepressor sensory outflow in pithed rats: correlation with alpha(2A/2C)-adrenoceptors.

BACKGROUND AND PURPOSE: Resistance blood vessels are innervated by sympathetic and primary sensory nerves, which modulate vascular tone through the release of noradrenaline and calcitonin gene-related peptide (CGRP), respectively. Moreover, electrical stimulation of the perivascular sensory outflow in pithed rats results in vasodepressor responses which are mainly mediated by CGRP release. The present study has investigated the role of alpha(2)-adrenoceptors in the inhibition of these vasodepressor responses. EXPERIMENTAL APPROACH: 144 pithed male Wistar rats were pretreated with hexamethonium (2 mg kg(-1) min(-1)) followed by i.v. continuous infusions of either methoxamine (15 and 30 microg kg(-1) min(-1)) or clonidine (3, 10 and 30 microg kg(-1) min(-1)). Under these conditions, electrical stimulation (0.56-5.6 Hz; 50 V and 2 ms) of the spinal cord (T(9)-T(12)) resulted in frequency-dependent decreases in diastolic blood pressure. KEY RESULTS: The infusion of clonidine (10 microg kg(-1) min(-1)), as compared to those of methoxamine (15 or 30 microg kg(-1) min(-1)), inhibited the vasodepressor responses to electrical stimulation without affecting those to i.v. bolus injections of alpha-CGRP (0.1-1 microg kg(-1)). This inhibition by clonidine was: (i) antagonized by 300 microg kg(-1) rauwolscine (alpha(2A/2B/2C)), 300 and 1000 microg kg(-1) BRL44408 (alpha(2A)), or 10 and 30 microg kg(-1) MK912 (alpha(2C)); and (ii) unaffected by 1 ml kg(-1) saline, 100 microg kg(-1) BRL44408, 3000 and 10,000 microg kg(-1) imiloxan (alpha(2B)) or 3 microg kg(-1) MK912. CONCLUSIONS AND IMPLICATIONS: The inhibition produced by 10 microg kg(-1) min(-1) clonidine on the vasodepressor (perivascular) sensory outflow in rats may be mainly mediated by prejunctional alpha(2A)/alpha(2C)-adrenoceptors.

Characterization of the postjunctional alpha 2C-adrenoceptor mediating vasoconstriction to UK14304 in porcine pulmonary veins.

BACKGROUND AND PURPOSE: In terms of postjunctional alpha(2)-adrenoceptors in the pulmonary circulation, no evidence is available with regard to the receptor subtypes mediating vasoconstriction. Therefore, we characterized the alpha(2)-adrenoceptor subtypes mediating contraction in isolated porcine pulmonary veins. EXPERIMENTAL APPROACH: alpha-adrenoceptor-mediated vasoconstriction was studied using a tissue bath protocol. mRNA profile and relative quantification of alpha(2)-adrenoceptor subtypes were determined in porcine pulmonary veins using reverse-transcriptase polymerase chain reaction (RT-PCR) and real-time PCR. KEY RESULTS: In porcine pulmonary veins, noradrenaline, phenylephrine (alpha(1)-adrenoceptor agonist), UK14304 and clonidine (alpha(2)-adrenoceptor agonists) caused concentration-dependent contractions. The rank order of agonist potency was: NA approximately UK14304 approximately clonidine > phenylephrine. UK14304 responses were antagonised by MK912 (noncompetitive antagonist parameter pD'(2): 10.1), rauwolscine (pK(B): 9.5), yohimbine (pK(B): 9.1), WB4101 (pK(B): 8.7), ARC239 (pK(B): 7.5), prazosin (pK(B): 7.1) and BRL44408 (pK(B): 7.0). Antagonist potencies fitted best with radioligand binding data (pK(i)) at the human recombinant alpha(2C)-adrenoceptor (r(2)=0.96, P=0.0001). Correlation with alpha(2B)-adrenoceptors was lower (r(2)=0.74, P>0.01) and no correlation was obtained with alpha(2A)-adrenoceptors. Moreover, RT-PCR studies in porcine pulmonary veins showed mRNA signals for alpha(2A)- and alpha(2C)-adrenoceptors, but not for alpha(2B)-adrenoceptors, whilst real-time PCR studies indicated a prominent expression of alpha(2C)-adrenoceptor mRNA. CONCLUSIONS AND IMPLICATIONS: Postjunctional alpha(2C)-adrenoceptors mediated contraction in porcine pulmonary veins. alpha(1)-Adrenoceptors also seem to be present in this tissue. Since alpha(2)-adrenoceptor responsiveness is increased when pulmonary vascular tone is elevated, alpha(2C)-adrenoceptor antagonists may be beneficial in diseases such as pulmonary hypertension or congestive heart failure.

Donitriptan, but not sumatriptan, inhibits capsaicin-induced canine external carotid vasodilatation via 5-HT1B rather than 5-HT1D receptors.

BACKGROUND AND PURPOSE: It has been suggested that during a migraine attack capsaicin-sensitive trigeminal sensory nerves release calcitonin gene-related peptide (CGRP), resulting in cranial vasodilatation and central nociception; hence, trigeminal inhibition may prevent this vasodilatation and abort migraine headache. This study investigated the effects of the agonists sumatriptan (5-HT(1B/1D) water-soluble), donitriptan (5-HT(1B/1D) lipid-soluble), PNU-142633 (5-HT(1D) water-soluble) and PNU-109291 (5-HT(1D) lipid-soluble) on vasodilator responses to capsaicin, alpha-CGRP and acetylcholine in dog external carotid artery. EXPERIMENTAL APPROACH: 59 vagosympathectomized dogs were anaesthetized with sodium pentobarbitone. Blood pressure and heart rate were recorded with a pressure transducer, connected to a cannula inserted into a femoral artery. A precalibrated flow probe was placed around the common carotid artery, with ligation of the internal carotid and occipital branches, and connected to an ultrasonic flowmeter. The thyroid artery was cannulated for infusion of agonists. KEY RESULTS: Intracarotid infusions of capsaicin, alpha-CGRP and acetylcholine dose-dependently increased blood flow through the carotid artery. These responses remained unaffected after intravenous (i.v.) infusions of sumatriptan, PNU-142633, PNU-109291 or physiological saline; in contrast, donitriptan significantly attenuated the vasodilator responses to capsaicin, but not those to alpha-CGRP or acetylcholine. Only sumatriptan and donitriptan dose-dependently decreased the carotid blood flow. Interestingly, i.v. administration of the antagonist, SB224289 (5-HT(1B)), but not of BRL15572 (5-HT(1D)), abolished the inhibition by donitriptan. CONCLUSIONS AND IMPLICATIONS: Our results suggest that the inhibition produced by donitriptan of capsaicin-induced external carotid vasodilatation is mainly mediated by 5-HT(1B), rather than 5-HT(1D), receptors, probably by a central mechanism.

Experimental migraine models and their relevance in migraine therapy.

Although the understanding of migraine pathophysiology is incomplete, it is now well accepted that this neurovascular syndrome is mainly due to a cranial vasodilation with activation of the trigeminal system. Several experimental migraine models, based on vascular and neuronal involvement, have been developed. Obviously, the migraine models do not entail all facets of this clinically heterogeneous disorder, but their contribution at several levels (molecular, in vitro, in vivo) has been crucial in the development of novel antimigraine drugs and in the understanding of migraine pathophysiology. One important vascular in vivo model, based on an assumption that migraine headache involves cranial vasodilation, determines porcine arteriovenous anastomotic blood flow. Other models utilize electrical stimulation of the trigeminal ganglion/nerve to study neurogenic dural inflammation, while the superior sagittal sinus stimulation model takes into account the transmission of trigeminal nociceptive input in the brainstem. More recently, the introduction of integrated models, namely electrical stimulation of the trigeminal ganglion or systemic administration of capsaicin, allows studying the activation of the trigeminal system and its effect on the cranial vasculature. Studies using in vitro models have contributed enormously during the preclinical stage to characterizing the receptors in cranial blood vessels and to studying the effects of several putative antimigraine agents. The aforementioned migraine models have advantages as well as some limitations. The present review is devoted to discussing various migraine models and their relevance to antimigraine therapy.

Lack of effect of the adenosine A1 receptor agonist, GR79236, on capsaicin-induced CGRP release in anaesthetized pigs.

Migraine is a common neurological disorder that is associated with an increase in plasma calcitonin gene-related peptide (CGRP) levels. CGRP, a potent vasodilator released from the activated trigeminal sensory nerves, dilates intracranial blood vessels and transmits vascular nociception. Hence, inhibition of trigeminal CGRP release may prevent neurotransmission and, thereby, ameliorate migraine headache. Therefore, the present study in anaesthetized pigs investigates the effects of a selective adenosine A(1) receptor agonist, GR79236 (3, 10 and 30 microg/kg, i.v.) on capsaicin-induced carotid haemodynamic changes and on plasma CGRP release. Intracarotid (i.c.) infusion of capsaicin (10 microg/kg/min, i.c.) increased the total carotid blood flow and conductance as well as carotid pulsations, but decreased the difference between arterial and jugular venous oxygen saturations. These responses to capsaicin were dose-dependently attenuated by GR79236. However, the increases in the plasma CGRP concentrations by capsaicin remained essentially unmodified after GR79236 treatment. The above results suggest that GR79236 may have an antimigraine potential due to its postjunctional effects (carotid vasoconstriction) rather than to prejunctional inhibition of trigeminal CGRP release.

An introduction to migraine: from ancient treatment to functional pharmacology and antimigraine therapy.

Migraine treatment has evolved from the realms of the supernatural into the scientific arena, but it seems still controversial whether migraine is primarily a vascular or a neurological dysfunction. Irrespective of this controversy, the levels of serotonin (5-hydroxytryptamine; 5-HT), a vasoconstrictor and a central neurotransmitter, seem to decrease during migraine (with associated carotid vasodilatation) whereas an i.v. infusion of 5-HT can abort migraine. In fact, 5-HT as well as ergotamine, dihydroergotamine and other antimigraine agents invariably produce vasoconstriction in the external carotid circulation. The last decade has witnessed the advent of sumatriptan and second generation triptans (e.g. zolmitriptan, rizatriptan, naratriptan), which belong to a new class of drugs, now known as 5-HT1B/1D/1F receptor agonists. Compared to sumatriptan, the second-generation triptans have a higher oral bioavailability and longer plasma half-life. In line with the vascular and neurogenic theories of migraine, all triptans produce selective carotid vasoconstriction (via 5-HT1B receptors) and presynaptic inhibition of the trigeminovascular inflammatory responses implicated in migraine (via 5-HT1D/5-ht1F receptors). Moreover, selective agonists at 5-HT1D (PNU-142633) and 5-ht1F (LY344864) receptors inhibit the trigeminovascular system without producing vasoconstriction. Nevertheless, PNU-142633 proved to be ineffective in the acute treatment of migraine, whilst LY344864 did show some efficacy when used in doses which interact with 5-HT1B receptors. Finally, although the triptans are effective antimigraine agents producing selective cranial vasoconstriction, efforts are being made to develop other effective antimigraine alternatives acting via the direct blockade of vasodilator mechanisms (e.g. antagonists at CGRP receptors, antagonists at 5-HT7 receptors, inhibitors of nitric oxide biosynthesis, etc). These alternatives will hopefully lead to fewer side-effects.

Evidence for 5-HT(1B/1D) and 5-HT(2A) receptors mediating constriction of the canine internal carotid circulation.

The present study has investigated the preliminary pharmacological profile of the receptors mediating vasoconstriction to 5-hydroxytryptamine (5-HT) in the internal carotid bed of vagosympathectomised dogs. One minute intracarotid infusions of the agonists 5-HT (0.1 - 10 microg min(-1)), sumatriptan (0.3 - 10 microg min(-1); 5-HT(1B/1D)), 5-methoxytryptamine (1 - 100 microg min(-1); 5-HT(1), 5-HT(2), 5-HT(4), 5-ht(6) and 5-HT(7)) or DOI (0.31 - 10 microg min(-1); 5-HT(2)), but not 5-carboxamidotryptamine (0.01 - 0.3 microg min(-1); 5-HT(1), 5-ht(5A) and 5-HT(7)), 1-(m-chlorophenyl)-biguanide (mCPBG; 1 - 1000 microg min(-1); 5-HT(3)) or cisapride (1 - 1000 microg min(-1); 5-HT(4)), resulted in dose-dependent decreases in internal carotid blood flow, without changing blood pressure or heart rate. The vasoconstrictor responses to 5-HT, which remained unaffected after saline, were resistant to blockade by i.v. administration of the antagonists ritanserin (100 microg kg(-1); 5-HT(2A/2B/2C)) in combination with tropisetron (3000 microg kg(-1); 5-HT(3/4)) or the cyclo-oxygenase inhibitor, indomethacin (5000 microg kg(-1)), but were abolished by the 5-HT(1B/1D) receptor antagonist, GR127935 (30 microg kg(-1)). Interestingly, after administration of GR127935, the subsequent administration of ritanserin unmasked a dose-dependent vasodilator component. GR127935 or saline did not practically modify the vasoconstrictor effects of 5-MeO-T. In animals receiving GR127935, the subsequent administration of ritanserin abolished the vasoconstrictor responses to 5-MeO-T unmasking a dose-dependent vasodilator component. The vasoconstriction induced by sumatriptan was antagonized by GR127935, but not by ritanserin. Furthermore, ritanserin (100 microg kg(-1)) or ketanserin (100 microg kg(-1); 5-HT(2A)), but not GR127935, abolished DOI-induced vasoconstrictor responses. The above results suggest that 5-HT-induced internal carotid vasoconstriction is predominantly mediated by 5-HT(1B/1D) and 5-HT(2A) receptors.

The GR127935-sensitive 5-HT(1) receptors mediating canine internal carotid vasoconstriction: resemblance to the 5-HT(1B), but not to the 5-HT(1D) or 5-ht(1F), receptor subtype.

This study has further investigated the pharmacological profile of the GR127935-sensitive 5-HT(1) receptors mediating vasoconstriction in the internal carotid bed of anaesthetized vagosympathectomized dogs. One-minute intracarotid infusions of the agonists 5-hydroxytryptamine (5-HT; 0.1 - 10 microg min(-1); endogenous ligand) and sumatriptan (0.3 - 10 microg min(-1); 5-HT(1B/1D)), but not PNU-142633 (1 - 1000 microg min(-1); 5-HT(1D)) or LY344864 (1 - 1000 microg min(-1); 5-ht(1F)), produced dose-dependent decreases in internal carotid blood flow without changing blood pressure or heart rate. The responses to 5-HT were apparently resistant to blockade by i.v. administration of the antagonists SB224289 (300 microg kg(-1); 5-HT(1B)), BRL15572 (300 microg kg(-1); 5-HT(1D)) or ritanserin (100 microg kg(-1); 5-HT(2)). In contrast, the responses to sumatriptan were antagonized by SB224289, but not by BRL15572. In the animals receiving SB224289, but not those receiving BRL15572, the subsequent administration of ritanserin abolished the 5-HT-induced vasoconstriction and unmasked a vasodilator component. Similarly, in ritanserin-treated animals, the subsequent administration of SB224289, but not BRL15572, completely blocked the 5-HT-induced vasoconstriction, revealing vasodilatation. In animals receiving initially BRL15572, the subsequent administration of SB224289 did not affect (except at 10 microg min(-1)) the vasoconstrictor responses to 5-HT. Notably, in animals pretreated with 1000 microg kg(-1) of mesulergine, a 5-HT(2/7) receptor antagonist, 5-HT produced a dose-dependent vasoconstriction, which was practically abolished by SB224289. After BRL15572, no further blockade was produced and the subsequent administration of ritanserin was similarly inactive. These results suggest that the GR127935-sensitive 5-HT(1) receptors mediating canine internal carotid vasoconstriction resemble the 5-HT(1B) but not the 5-HT(1D) or 5-ht(1F), receptor subtype.

Unravelling the pharmacological profile of the canine external carotid vasodilator '5-HT1-like' receptors: coexistence of sympatho-inhibitory 5-HT1B and postjunctional 5-HT7 receptors.

It has been suggested that the external carotid vasodilatation produced by serotonin (5-hydroxytryptamine; 5-HT) in anaesthetised dogs with intact vagosympathetic trunks is mediated by sympatho-inhibitory '5-HT1D' receptors and musculotropic '5-HT1-like' receptors. The present study has re-analysed this suggestion with regard to the classification schemes recently proposed by the NC-IUPHAR subcommittee on 5-HT receptors. In pentobarbital-anaesthetised dogs with intact vagosympathetic trunks, 1-min intracarotid (i.c.) infusions of 5-carboxamidotryptamine (5-CT; 0.01-0.3 microg/min), 5-HT (0.3-30 microg/ min), 5-methoxytryptamine (5-MeO-T; 1-100 microg/min) or sumatriptan (1-100 microg/min) dose-dependently increased the external carotid blood flow without affecting blood pressure or heart rate. The selective 5-HT1D receptor agonist, PNU-142633 (1-1000 microg/min), was essentially inactive. After mesulergine (300 microg/kg, i.v.), an antagonist at cardiovascular 5-HT7 receptors, the above responses to 5-HT, 5-CT and 5-MeO-T were blocked, whilst those to sumatriptan remained unaffected. In contrast, after the 5-HT1B/1D receptor antagonist, GR127935 (10 microg/kg, i.v.), the responses to 5-HT, 5-CT and 5-MeO-T were not affected, but those to sumatriptan were abolished. Furthermore, after the selective 5-HT1B receptor antagonist, SB224289 (300 microg/kg, i.v.), the responses to 5-HT, 5-CT and 5-MeO-T were significantly enhanced, whereas those to sumatriptan were abolished. Interestingly, the responses to all these agonists remained unmodified after the selective 5-HT1D receptor antagonist, BRL15572 (300 microg/kg, i.v.). The above results suggest that the '5-HT1-like' receptors, which mediate canine external carotid vasodilatation, display the pharmacological profile of sympatho-inhibitory 5-HT1B receptors and musculotropic 5-HT7 receptors, and confirm the existence of vasoconstrictor 5-HT1B receptors.

Survival and characterization of Escherichia coli strains in a typical Mexican acid-fermented food.

In this study, the presence and pathogenic characteristics of Escherichia coli strains in pozol, an acid-fermented maize beverage consumed in South-eastern Mexico, were determined. Seventy-three E. coli strains were isolated at early and late times (6 and 48 h) during the pozol fermentation process, when pH values of the doughs were 6.7-4.7 (6 h) and 4.7-3.7 (48 h). Serotypes that belong to diarrheagenic E. coli serogroups O18, O88, O8, O11, O20, O173 were identified. HEp-2 cell adherence in vitro assays showed localized, diffuse and aggregative adherence patterns among some of these strains. A DNA colony hybridization analysis with different probes showed the presence of virulence genes related to diarrheal pathogenesis. Thirty-three percent of the E. coli strains were tetracycline-resistant and 95% had a 20 kb plasmid. The presence and survival of potentially pathogenic E. coli in acid-fermented pozol suggest that such foods may be a potential source of foodborne outbreaks.

Mediation of 5-HT-induced internal carotid vasodilatation in GR127935- and ritanserin-pretreated dogs by 5-HT7 receptors.

The vasoconstrictor effects of 5-hydroxytryptamine (5-HT) in the internal carotid bed of anaesthetised dogs with bilateral vagosympathectomy are mainly mediated by both 5-HT1B and 5-HT2 receptors. The blockade of this vasoconstrictor effect of 5-HT by the combined use of the antagonists, GR127935 (5-HT1B/1D) and ritanserin (5-HT2), unmasks a dose-dependent vasodilator effect of 5-HT, but not of sumatriptan. Therefore, the present study set out to analyse the pharmacological profile of this vasodilator 5-HT receptor in the internal carotid bed of vagosympathectomized dogs systematically pretreated with intravenous (i.v.) injections of GR127935 (30 microg/kg) and ritanserin (100 microg/kg). One-minute (1-min) intracarotid (i.c.) infusions of 5-HT (0.1-10 microg/min), 5-carboxamidotryptamine (5-CT; 0.01-0.3 microg/min), 5-methoxytryptamine (5-MeO-T; 1-100 microg/min) and acetylcholine (ACh; 0.003-0.1 microg/min) resulted in dose-dependent increases in internal carotid blood flow (without changes in blood pressure or heart rate) with a rank order of agonist potency of ACh > 5-CT >> 5-HT > or =5-MeO-T. The internal carotid vasodilator responses to 5-HT, 5-CT and 5-MeO-T, which remained unaffected after saline (0.03 ml/kg and 0.1 ml/kg, i.v.), were specifically and dose-dependently blocked by i.v. administration of lisuride (10 microg/kg and 30 microg/kg), clozapine (1000 microg/kg), mesulergine (300 microg/kg and 1000 microg/kg) and LY215840 (300 microg/kg and 1000 microg/kg) with the following apparent rank order of potency: lisuride >> mesulergine = LY215840 > or = clozapine. The above results suggest that the 5-HT receptor mediating internal carotid vasodilatation in vagosympathectomized dogs pretreated with GR127935 and ritanserin is operationally similar to other 5-HT7 receptors mediating vascular and non-vascular responses.

Further pharmacological analysis of the orphan 5-HT receptors mediating feline vasodepressor responses: close resemblance to the 5-HT7, receptor.

It has been suggested that the late hypotensive response to serotonin (5-hydroxytryptamine; 5-HT) in vagosympathectomised cats, being potently mimicked by 5-carboxamidotryptamine (5-CT), not modified by ketanserin and blocked by methiothepin or methysergide, is mediated by '5-HT1-like' receptors. Nevertheless, current guidelines for 5-HT receptor classification refer to this receptor as an orphan receptor. Thus, the present study set out to reanalyse the above suggestion in terms of the classification schemes proposed in 1994 and 1998 by the NC-IUPHAR subcommittee on the classification of 5-HT receptors. Intravenous (i.v.) bolus injections of 5-CT (0.003-0.3 microg/kg), 5-HT (1-100 microg/kg) and 5-methoxytryptamine (5-MeO-T; 1-100 microg/kg) produced dose-dependent vasodepressor responses with a rank order of agonist potency of 5-CT >> 5-HT = 5-MeO-T with sumatriptan (10-300 microg/kg) virtually inactive. The vasodepressor responses to 5-HT, 5-CT and 5-MeO-T were not attenuated following i.v. administration of the antagonists GR127935 (5-HT(IB/ID); 30 microg/kg), tropisetron (5-HT3/4; 3000 microg/kg), (+/-)-pindolol (beta-adrenergic and 5-HT1A; 4000 microg/kg) or equivalent volumes of physiological saline. In contrast, the above vasodepressor responses were markedly and specifically antagonised by i.v. methiothepin (100 microg/kg), lisuride (30 microg/kg and 100 microg/kg), mesulergine (300 microg/kg and 1000 microg/kg) or LY215840 (300 microg/kg and 1000 microg/kg). The above lines of evidence, therefore, indicate that the orphan receptors mediating the vasodepressor responses to 5-HT in vagosympathectomised cats are pharmacologically similar to other 5-HT7 receptors mediating vascular and non-vascular responses (e.g. relaxation of the canine external carotid artery and guinea-pig ileum as well as feline tachycardia).

5-Hydroxytryptamine inhibits the tachycardia induced by selective preganglionic sympathetic stimulation in pithed rats.

It has been shown in several species that serotonin (5-hydroxytryptamine; 5-HT) is able to inhibit the responses produced by sympathetic stimulation in a wide variety of blood vessels and other organs, including the heart. However, in pithed rats, the analysis of potential sympatho-inhibitory actions of 5-HT is hampered by the fact that 5-HT (given as i.v. bolus injections) produces tachycardia per se. Moreover, most studies have investigated 5-HT-induced sympatho-inhibition at only one frequency of stimulation. Thus, the present study set out to find the experimental conditions to overcome these problems. In this regard, we analyzed the potential ability of 5-HT, administered as i.v. continuous infusions, to inhibit the tachycardia caused by stimulation of the preganglionic (C7-T1) sympathetic outflow in pithed rats. Sympathetic cardiostimulation (0.01-3 Hz) resulted in frequency-dependent increases in heart rate; these responses were potentiated after desipramine (50 microg/kg, i.v.). During continuous infusions of 5-HT (3.1-10 microg/kg.min, i.v.), but not saline, the sympathetically-induced tachycardia was dose-dependently inhibited in both control and desipramine-pretreated rats. This inhibitory effect of 5-HT was significantly more pronounced at lower frequencies of stimulation. In contrast, the above infusions of 5-HT did not inhibit the tachycardia induced by i.v. bolus injections of noradrenaline in both control and desipramine-pretreated rats. Taken together, the above findings confirm that 5-HT induces inhibition of the sympathetic chronotropic outflow in the rat by acting at receptors located prejunctionally, without evoking tachycardia, over a wide range of stimulation frequencies.

Canine external carotid vasoconstriction to methysergide, ergotamine and dihydroergotamine: role of 5-HT1B/1D receptors and alpha2-adrenoceptors.

The antimigraine drugs methysergide, ergotamine and dihydroergotamine (DHE) produce selective vasoconstriction in the external carotid bed of vagosympathectomized dogs anaesthetized with pentobarbital and artificially respired, but the receptors involved have not yet been completely characterized. Since the above drugs display affinity for several binding sites, including alpha-adrenoceptors and several 5-HT1 and 5-HT2 receptor subtypes, this study has analysed the mechanisms involved in the above responses. Intracarotid (i.c.) infusions during 1 min of methysergide (31-310 microg min(-1)), ergotamine (0.56-5.6 microg min(-1)) or DHE (5.6-31 microg min(-1)) dose-dependently reduced external carotid blood flow (ECBF) by up to 46+/-4, 37+/-4 and 49+/-5%, respectively. Blood pressure and heart rate remained unchanged. The reductions in ECBF by methysergide were abolished and even reversed to increases in animals pre-treated with GR127935 (10 microg kg(-1), i.v.). The reductions in ECBF by ergotamine and DHE remained unchanged in animals pre-treated (i.v.) with prazosin (300 microg kg(-1)), but were partly antagonized in animals pre-treated with either GR127935 (10 or 30 microg kg(-1)) or yohimbine (1000 microg kg(-1)). Pre-treatment with a combination of GR127935 (30 microg kg(-1)) and yohimbine (1000 microg kg(-1)) abolished the responses to both ergotamine and DHE. The above doses of antagonists were shown to produce selective antagonism at their respective receptors. These results suggest that the external carotid vasoconstrictor responses to methysergide primarily involve 5-HT1B/1D receptors, whereas those to ergotamine and DHE are mediated by 5-HT1B/1D receptors as well as alpha2-adrenoceptors.

5-HT receptors mediating external carotid vasoconstriction in vagosympathectomized dogs.

One specific example reflecting the complexity of cardiovascular responses induced by serotonin (5-hydroxytryptamine; 5-HT) and the progress achieved in the pharmacological characterization of the receptors involved can be illustrated by the effects of 5-HT on the canine external carotid artery bed. Within this framework, it has been shown that the external carotid vasoconstrictor response to 5-HT in the dog is mediated by '5-HT1-like' receptors, which being blocked by the 5-HT1B/1D receptor antagonist GR127935, resemble 5-HT1B/1D (previously called 5-HT1D beta/1D alpha) receptors. It was proposed that these receptors could belong to the 5-HT1B, rather than the 5-HT1D, subtype on the basis of their resistance to blockade by a high dose of ritanserin (a potential 5-HT1D receptor antagonist) and the presence of mRNA for 5-HT1B(5-HT1D beta) receptors, but not for 5-HT1D(5-HT1D alpha) receptors, in vascular smooth muscle. With the advent of subtype-selective antagonists it was subsequently shown that external carotid vasoconstriction to 5-HT and sumatriptan is dose-dependently antagonized by the selective 5-HT1B receptor antagonist SB224289 (2,3,6,7-tetrahydro-1'-methyl-5-[2'-methyl-4' (5-methyl-1,2,4-oxadiazol-3-yl) biphenyl-4-carbonyl] furo [2,3-f] indole-3-spiro-4'-piperidine hydrochloride), whereas the selective 5-HT1D receptor antagonist BRL15572 (1-(3-chlorophenyl)-4-[3,3-diphenyl (2-(S,R) hydroxypropanyl) piperazine] hydrochloride) was ineffective. These findings represent the first in vivo evidence showing that vascular constriction induced by 5-HT and sumatriptan is mediated primarily via 5-HT1B, but not 5-HT1D receptors. The pharmacological profile of these receptors could be similar (isolated human temporal artery and porcine carotid arteriovenous anastomoses) to other putative 5-HT1B receptors mediating vasoconstrictor responses. In view of the putative pathophysiologic role of external carotid (and extracerebral) vasodilation in migraine, the constriction of these blood vessels by sumatriptan via 5-HT1B receptors may be, at least partly, responsible for its therapeutic efficacy in migraine.

The canine external carotid vasoconstrictor 5-HT1 receptor: blockade by 5-HT1B (SB224289), but not by 5-HT1D (BRL15572) receptor antagonists.

In vagosympathectomised dogs pre-treated intravenously (i.v.) with mesulergine (300 microg/kg), 1-min intracarotid (i.c.) infusions of 5-hydroxytryptamine (5-HT; 0.3-30 microg/min) and sumatriptan (1-30 microg/min) dose-dependently decreased external carotid blood flow, without affecting mean blood pressure or heart rate. Treatment with the selective 5-HT1B receptor antagonist SB224289 (2,3,6,7-tetrahydro-1'-methyl-5-[2'-methyl-4'(5-methyl-1,2,4-oxadiazo l-3-yl) biphenyl-4-carbonyl]furo[2,3f]indole-3-spiro-4'-piperidine hydrochloride; 30-300 microg/kg, i.v.) produced a potent, specific and dose-dependent blockade of this response, whereas the selective 5-HT1D receptor antagonist BRL15572 (1-(3-chlorophenyl)-4-[3,3-diphenyl(2-(S,R) hydroxypropanyl)piperazine]hydrochloride; 30-300 microg/kg, i.v.) was ineffective. It is concluded that mainly 5-HT1B, but not 5-HT1D receptors mediate the canine external carotid vasoconstriction by 5-HT and sumatriptan.

The 5-HT1-like receptors mediating inhibition of sympathetic vasopressor outflow in the pithed rat: operational correlation with the 5-HT1A, 5-HT1B and 5-HT1D subtypes.

1. It has been suggested that the inhibition of sympathetically-induced vasopressor responses produced by 5-hydroxytryptamine (5-HT) in pithed rats is mediated by 5-HT1-like receptors. The present study has re-analysed this suggestion with regard to the classification schemes recently proposed by the NC-IUPHAR subcommittee on 5-HT receptors. 2. Intravenous (i.v.) continuous infusions of 5-HT and the 5-HT1 receptor agonists, 8-OH-DPAT (5-HT1A), indorenate (5-HT1A), CP 93,129 (5-HT1B) and sumatriptan (5-HT(1B/1D)), resulted in a dose-dependent inhibition of sympathetically-induced vasopressor responses. 3. The sympatho-inhibitory responses induced by 5-HT, 8-OH-DPAT, indorenate, CP 93,129 or sumatriptan were analysed before and after i.v. treatment with blocking doses of the putative 5-HT receptor antagonists, WAY 100635 (5-HT1A), cyanopindolol (5-HT(1A/1B)) or GR 127935 (5-HT(1B/1D)). Thus, after WAY 100635, the responses to 5-HT and indorenate, but not to 8-OH-DPAT, CP 93,129 and sumatriptan, were blocked. After cyanopindolol, the responses to 5-HT, indorenate and CP 93,129 were abolished, whilst those to 8-OH-DPAT and sumatriptan (except at the lowest frequency of stimulation) remained unaltered. In contrast, after GR 127935, the responses to 5-HT, CP 93,129 and sumatriptan, but not to 8-OH-DPAT and indorenate, were abolished. 4. In additional experiments, the inhibition induced by 5-HT was not modified after 5-HT7 receptor blocking doses of mesulergine. 5. The above results suggest that the 5-HT1-like receptors, which inhibit the sympathetic vasopressor outflow in pithed rats, display the pharmacological profile of the 5-HT1A, 5-HT1B and 5-HT1D, but not that of 5-HT7, receptors.