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G Porras

Publications and source records attributed to G Porras.

6 recordsLinked to original sources
PubMed2001

Neurochemical and electrophysiological evidence that 5-HT4 receptors exert a state-dependent facilitatory control in vivo on nigrostriatal, but not mesoaccumbal, dopaminergic function.

In this study we investigated, using in vivo microdialysis and single unit recordings, the role of serotonin4 (5-HT4) receptors in the control of nigrostriatal and mesoaccumbal dopaminergic (DA) pathway activity. In freely moving rats, the 5-HT4 antagonist GR 125487 (1 mg/kg, i.p.), without effect on its own, significantly reduced the enhancement of striatal DA outflow induced by 0.01 (-35%) and 0.1 (-66%), but not 1 mg/kg, s.c. haloperidol (HAL). Intrastriatal infusion of GR 125487 (1 microM) had no influence on basal DA outflow, but attenuated (-49%) the effect of 0.01 mg/kg HAL. Systemic administration of GR 125487 modified neither basal nor 0.01 mg/kg HAL-stimulated accumbal DA outflow. In halothane-anaesthetized rats, 1 or 10 mg/kg GR 125487, without effect by itself, failed to modify the changes in accumbal and striatal DA outflow elicited by electrical stimulation (300 microA, 1 ms, 20 Hz, 15 min) of the dorsal raphe nucleus. Finally, GR 125487 (444 microg/kg, i.v.), whilst not affecting basal firing of DA neurons within either the substantia nigra or the ventral tegmental area, reduced HAL-stimulated (1--300 microg/kg, i.v.) impulse flow of nigrostriatal DA neurons only. These results indicate that 5-HT4 receptors exert a facilitatory control on both striatal DA release and nigral DA neuron impulse flow only when nigrostriatal DA transmission is under activated conditions. Furthermore, they indicate that the striatum constitutes a major site for the expression of the control exerted by 5-HT4 receptors on DA release. In contrast, 5-HT4 receptors have no influence on mesoaccumbal DA activity in either basal or activated conditions.

Action Potentials↗
PubMed2000

Endogenous serotonin enhances the release of dopamine in the striatum only when nigro-striatal dopaminergic transmission is activated.

In this study, we use in vivo microdialysis to investigate the influence of endogenous serotonin (5-HT) on striatal dopamine (DA) and 5-hydroxyidoleacetic acid (5-HIAA) efflux in both basal and activated conditions. The selective serotonin reuptake inhibitors citalopram and fluoxetine were used to mobilize endogenous 5-HT. In halothane-anaesthetized rats, citalopram (5 mg/kg, i.p.), administered either alone or in combination with the 5-HT(1A) receptor antagonist WAY 100635 (0.1 mg/kg, s.c.), while reducing striatal 5-HIAA outflow (-25 and -15%, respectively), had no effect on basal DA output. When locally applied into the striatum, citalopram had no effect at 1 microM concentration, but enhanced DA release after its perfusion at 25 and 100 mircroM concentrations (+27% and +67%, respectively). However, the injection of the neurotoxin 5,7-dihydroxytryptamine into the dorsal raphe nucleus, which markedly depleted 5-HT in the striatum, failed to modify the effect of 25 microM citalopram. In freely-moving rats, the intrastriatal infusion of citalopram or fluoxetine (1 microM each), had no effect on its own, but significantly enhanced the increase in DA outflow induced by the subcutaneous administration of 0.01 mg/kg haloperidol (+31% and +30% for citalopram and fluoxetine, respectively). These findings indicate that, in the striatum, endogenous 5-HT has no influence on DA release under basal conditions, but positively modulates DA outflow when nigro-striatal DA transmission is activated.

5,7-Dihydroxytryptamine↗
PubMed1997

Selecting the surgical procedure for simple and complicated esophageal achalasia in children.

BACKGROUND/PURPOSE: Surgical experience in children who have achalasia is limited. Surgical treatment requires esophagocardiomyotomy and an antireflux procedure. However, when these operations fail, other procedures are needed. To summarize the experience treating children who have this condition, the authors reviewed retrospectively all case histories of patients treated from 1971 to 1996 at their hospital. METHODS: Three boys and a girl, ranging in age from 18 months to 11 years, were treated. All had multiple previous dilatations. Two then underwent operation using an abdominal approach for a Heller procedure and a posterior fundoplasty (Guarner operation). Two children were previously treated in another hospital. One underwent a Heller operation complicated by perforation of the anterior mucosa. The other had undergone three previous abdominal approaches for esophagocardiomyotomy and a Nissen fundoplication. Symptoms persisted and imaging and endoscopy showed stenosis in both patients. In the first patient an esophagocardioplasty with transverse closure (Wendel procedure) and a posterior fundoplasty was performed. In the second child, the three previous abdominal surgical approaches mandated a transthoracic approach with transdiaphragmatic latero-lateral esophagogastric anastomosis (Heyrowsky operation) and a modified Guarner operation using the remaining fundus and gastric body. RESULTS: There were no intraoperative or postoperative complications. Follow-up time ranged from 3 months to 17 years. All patients experienced dramatic relief of symptoms and satisfactory weight gain. No recurrence of symptomatology has occurred. CONCLUSIONS: Esophagocardiotomy associated with an antireflux procedure may be the first option in the surgical treatment of children who have achalasia. However, if this fails, esophagocardioplasty and the latero-lateral esophagogastric anastomosis associated with antireflux procedure may be successful alternatives.

Anastomosis, Surgical↗
PubMed1996

[Ocular toxoplasmosis in human immunodeficiency virus infected patients without concurrent central nervous system infection. Report of two cases].

Ocular toxoplasmosis is an uncommon complication of acquired immunodeficiency syndrome (AIDS), and it is generally described associated with central nervous system (CNS) lesions. We describe two cases of ocular toxoplasmosis in human immunodeficiency virus (HIV) infected patients, without concurrent CNS infection. Both developed bilateral or unilateral choriorretinitis with favorable response to antitoxoplasma therapy. None of them presented toxoplasmosis of the CNS coexisting with ocular lesions. Ocular toxoplasmosis should be considered in HIV infected patients although no involvement of the CNS is found.

Adult↗