Hippocampal somatostatin receptors and modulation of adenylyl cyclase activity in histamine-treated rats

In the present study, the effects of an intracerebroventricular (i.c.v.) dose of histamine (0.1, 1.0 or 10.0 ¿g) on the hippocampal somatostatin (SS) receptor/effector system in Wistar rats were investigated. In view of the rapid onset of histamine action, the effects of histamine on the somatostatinergic system were studied 2 h after its administration. Hippocampal SS-like immunoreactivity (SSLI) levels were not modified by any of the histamine doses studied. SS-mediated inhibition of basal and forskolin (FK)-stimulated adenylyl cyclase (AC) activity was markedly increased in hippocampal membranes from rats treated with 10 ¿g of histamine (23% ± 1% vs. 17% ± 1% and 37% ± 2% vs. 23% ± 1%, respectively). In contrast, neither the basal nor the FK-stimulated enzyme activities were affected by histamine administration. The functional activity of the hippocampal guanine-nucleotide binding inhibitory protein (G(i) protein), as assessed by the capacity of the stable GTP analogue 5'-guanylylimidodiphosphate (Gpp[NH]p) to inhibit FK-stimulated AC activity, was not modified by histamine administration. These data suggest that the increased response of the enzyme to SS was not related to an increased functional activity of G(i) proteins. In fact, the increased AC response to SS in hippocampal membranes from histamine (10 ¿g)-treated rats was associated with quantitative changes in the SS receptors. Equilibrium binding data obtained with [125I]Tyr11-SS indicate an increase in the number of specific SS receptors (541 ± 24 vs. 365 ± 16 fmol/mg protein, P < 0.001) together with a decrease in their apparent affinity (0.57 ± 0.04 vs. 0.41 ± 0.03 nM, P < 0.05) in rat hippocampal membranes from histamine (10 ¿g)-treated rats as compared to control animals. With the aim of determining if these changes were related to histamine binding to its specific receptor sites, the histaminergic H1 and H2 receptor antagonists mepyramine and cimetidine, respectively, were administered 1 h before histamine injection. The pretreatment with mepyramine or cimetidine induced an increase in the number and affinity constant of the SS receptors whereas the simultaneous pretreatment with both histamine antagonists prevented the histamine-induced changes in SS binding to its receptors. Since the hippocampal SS receptor/effector system is modulated by histamine, it is tempting to speculate that in the hippocampus, SS could be involved as a mediator of the histamine effects on behaviors such as learning and memory.This work was supported by a Grant from the Dirección General de lnvestigación Científicay Técnica of Spain

Influence of fluoxetine and p-chloroamphetamine on the somatostatin receptor-adenylyl cyclase system in the rat frontoparietal cortex

There is evidence that suggests a reciprocal functional link between the serotonergic and the somatostatinergic system in the rat frontoparietal cortex. However, to date, the role of endogenous 5-hydroxytryptamine (serotonin) on the regulation of the somatostatin (SS) receptor-adenylyl cyclase (AC) system remains unclear. In the present study, the administration of fluoxetine (10 mg/kg i.p.), a 5-hydroxytryptamine uptake inhibitor in a single dose or administered daily for 14 days increased the number of specific [125I]Tyr11-SS receptors, with no change in the receptor affinity, in rat frontoparietal cortical membranes. However, the capacity of SS to inhibit forskolin (FK)-stimulated AC activity in these membranes was lower than in the control groups. The ability of the stable GTP analogue 5'-guanylylimidodiphosphate (Gpp(NH)p) to inhibit FK-stimulated AC activity in frontoparietal cortical membranes was also decreased in rats acutely and chronically treated with fluoxetine. p-Chloroamphetamine (5 mg/kg i.p.), which leads to a lasting reduction of 5-hydroxytryptamine innervation, administered,on days 1, 3 and 5 and the rats sacrificed 1 or 3 weeks after the first injection, decreased the number of SS receptors without changing the receptor affinity. In this experimental group, SS also caused a significantly lower inhibition of FK-stimulated AC activity. p-Chloroamphetamine had no effect on the ability of Gpp(NH)p to inhibit FK-stimulated AC activity in frontoparietal cortical membranes at all the time periods studied. The present results suggest that under normal circumstances some SS receptors are under a tonic stimulatory control through the serotonergic system

Las relaciones laborales a través del cine: incorporación de mejoras metodológicas en la enseñanza del derecho

Memoria ID-0052. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

Wikipedia como herramienta de aprendizaje en la docencia de derecho del trabajo y de la seguridad social

Memoria ID12-0223. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2012-2013

Propuesta metodológica para la zonificación funcional de áreas naturales protegidas terrestres desde la perspectiva del paisaje. Methodological proposal for functional zoning of terrestrial natural areas protected from the landscape perspective.

La división de un área natural protegida en zonas de manejo es un proceso arduo y complejo, para lo cual es necesario un sistema de evaluación y clasificación de la superficie del territorio en cuestión que permita el reconocimiento en el terreno de los sitios donde se llevarán a cabo las acciones para la protección y el manejo de los valores y recursos del área. El presente trabajo propone una guía metodológica que describe, analiza y privilegia como soporte teórico-metodológico la Geoecología de los Paisajes como vía para llegar a la propuesta de zonificación funcional de un Área Natural Protegida terrestre, partiendo de la delimitación, clasificación y cartografía de las unidades de paisaje con el empleo de los Sistemas de Información Geográfica; el análisis de algunas de las propiedades sistémicas de los paisajes y el cálculo de indicadores como naturalidad, heterogeneidad, peligro, estabilidad y sensibilidad entre otros, así como la evaluación de los potenciales y los conflictos de uso como parte del diagnóstico, permitirá realizar la propuesta de zonificación funcional con una visión integral del territorio y determinar para cada zona y subzona las acciones a desarrollar para mitigar los impactos, atenuar o eliminar las amenazas, mejorar la salud de los objetos de conservación y proteger los valores en cada una de las áreas identificadas con problemas.The division of a protected natural area in managed territories is a difficult and complex process for which an assessment and classification system of the surface of the territory, allowing the recognition of the places, where actions to protect the manage values and the resources of the area will be carried out, is necessary. This paper proposes a methodological guide, describes, assesses and favors, as a theoretical and methodological medium, the Geoecology of Landscapes as a means to reach the functional zoning proposal of a terrestrial protected area from defining, classifying and mapping landscape units with the use of GIS; the analysis of some of the systemic properties of landscapes and the calculation of indicators such as naturalness, diversity, danger, stability and sensitivity, among others, as well as the evaluation of the potentials and the use conflicts as part of the diagnosis to carry out the functional zoning proposal with a comprehensive approach of the territory and determine the steps to be taken to mitigate impacts, reduce or eliminate threats, improve the health of the objects of preservation and protect the values in every zone and sub-zon

5-Hydroxytryptamine decreases somatostatin receptors and somatostatin-responsive adenylyl cyclase in rat pancreatic acinar membranes

Pretreatment of pancreatic acini with 5-hydroxytryptamine (5-HT) reduced the binding of the labeled somatostatin (SS) analogue 125I-Tyr3-SMS to pancreatic acinar membranes. This effect was dependent of the dose of 5-HT used and length of pretreatment. This inhibitory effect of 5-HT was abolished when pancreatic acini were pretreated with 5-HT in the presence of the 5-HT1P receptor-antagonist 5-hydroxytryptophyl-5-hydroxytryptophan amide (5-HTP-DP). Pretreatment of pancreatic acini with 5-HT reduced the inhibition by the stable SS analogue SMS 201-995 of basal and forskolin (FK)-stimulated adenylyl cyclase (AC) activity in pancreatic acinar membranes. There was no statistical difference established between IC50 values for the stable GTP analogue 5'-guanylylimidodiphosphate (Gpp(NH)p) which inhibits ligand binding to SMS receptors in controls and in 5-HT treated pancreatic cells, respectively. In addition, no significant differences were seen in the level of Gi proteins in the control and 5-HT treated panceatic acini. These data suggest that the decrease of the number of 125I-Tyr3-SMS receptors, would explain the decreased sensitivity of AC to SMS 201-995 in membranes from 5-HT-pretreated acini

Effect of nitric oxide on the somatostatinergic system in the rat exocrine pancreas

Nitric oxide (NO) and somatostatin (SS) are two important mediators of the exocrine and endocrine pancreas, exerting opposite effects on this organ. There is strong evidence suggesting an interaction between pancreatic NO and SS. The aim of this study was to determine whether L-arginine (L-Arg), the substrate for NO synthase (NOS), and Nω-nitro-L-arginine methyl ester (L-NAME), a NOS inhibitor, regulate pancreatic somatostatin-like immunoreactivity (SSLI) content and the SS mechanism of action in pancreatic acinar cell membranes. L-Arg (150 mg/kg, intraperitoneally (i.p.)), L-NAME (50 mg/kg, i.p.) or L-NAME plus L-Arg were injected twice daily at 8 h intervals for 8 days. L-Arg decreased pancreatic SSLI content as well as the number of SS receptors in pancreatic acinar cell membranes whereas L-NAME increased both parameters. The stable SS analogue SMS 201-995 induced a significantly lower inhibition of forskolin-stimulated adenylyl cyclase activity in pancreatic acinar cell membranes from L-Arg-treated rats whereas an increased inhibition was observed in pancreatic acinar membranes from L-NAME-treated rats. These results indicate that the NO system may contribute to the regulation of the pancreatic somatostatinergic system

Cine y relaciones laborales: nuevas propuestas didácticas para la enseñanza

Memoria ID-0175. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2015-2016