Pomolic acid reduces contractility and modulates excitation-contraction coupling in rat cardiomyocytes.

Pomolic acid (PA) isolated from Licania pittieri has hypotensive effects in rats, inhibits human platelet aggregation and elicits endothelium-dependent relaxation in rat aortic rings. The present study was designed to investigate the effects of PA on cardiomyocytes. Trabeculae and enzymatically isolated cardiomyocytes from rats were used to evaluate the concentration-dependent effects of PA on cardiac muscle tension and excitation-contraction coupling (ECC) by recording Ca2+ transients reported with Fluo-3 and Fura-2, as well as L-type Ca2+ currents (LTCC). PA reduced the contractile force in rat cardiac trabeculae with an EC50 = 14.3 ±â€¯2.4 µM. PA also reduced the amplitude of Ca2+ transients in a concentration-dependent manner, with an EC50 = 10.5 ±â€¯1.3 µM, without reducing sarcoplasmic reticulum (SR) Ca2+ loading. PA decreased the half width of the Ca2+ transient by 31.7 ±â€¯3.3% and increased the decay time and decay time constant (τ) by 7.6 ±â€¯2.7% and 75.6 ±â€¯3.7%, respectively, which was associated with increased phospholamban (PLN) phosphorylation. PA also reversibly reduced the macroscopic LTCC in the cardiomyocyte membrane, but did not demonstrate any effects on skeletal muscle ECC. In conclusion, PA reduces LTCC, Ca2+ transients and cardiomyocyte force, which along with its vasorelaxant effects explain its hypotensive properties. Increased PLN phosphorylation protected the SR from Ca2+ depletion. Considering the effects of PA on platelet aggregation and the cardiovascular system, we propose it as a new potential, multitarget cardiovascular agent with a demonstrated safety profile.

Sodium-calcium exchanger modulates the L-glutamate Ca(i) (2+) signalling in type-1 cerebellar astrocytes.

We have previously demonstrated that rat type-1 cerebellar astrocytes express a very active Na(+)/Ca(2+) exchanger which accounts for most of the total plasma membrane Ca(2+) fluxes and for the clearance of Ca (i) (2+) induced by physiological agonist. In this chapter, we have explored the mechanism by which the reverse Na(+)/Ca(2+) exchange is involved in agonist-induced Ca(2+) signalling in rat cerebellar astrocytes. Laser-scanning confocal microscopy experiments using immunofluorescence labelling of Na(+)/Ca(2+) exchanger and RyRs demonstrated that they are highly co-localized. The most important finding presented in this chapter is that L-glutamate activates the reverse mode of the Na(+)/Ca(2+) exchange by inducing a Na(+) entry through the electrogenic Na(+)-glutamate co-transporter and not through the ionophoric L-glutamate receptors as confirmed by pharmacological experiments with specific blockers of ionophoric L-glutamate receptors, electrogenic glutamate transporters and the Na/Ca exchange.

The activity of the Na+/Ca2+ exchanger largely modulates the Ca2+i signal induced by hypo-osmotic stress in rat cerebellar astrocytes. The effect of osmolarity on exchange activity.

We recently demonstrated that rat cerebellar Type-1 astrocytes express a very active Na(+)/Ca(2+) exchanger highly colocalized with ryanodine receptors (RyRs), which in turn play a key role in glutamate-induced Ca(2+) signaling through a calcium-induced calcium release (CICR) mechanism. In this work we have explored whether the Na(+)/Ca(2+) exchanger has any role in the Ca(2+)(i) signal induced by hypo-osmotic stress in these cells, using microspectrofluorometric measurements with Fura-2, pharmacological tools, and confocal microscopy image analysis. We present evidence for the first time that the increase in [Ca(2+)](i) in rat cerebellar Type-1 astrocytes, resulting from moderate hypotonic shock, is mediated by Ca(2+) release from ryanodine-operated Ca(2+)(i) stores, and that the magnitude of the intracellular Ca(2+) signal induced by hypotonicity in the short term (up to 240 s) is small and controlled by the activity of the Na(+)/Ca(2+) exchanger operating in its extrusion mode. With longer times in the hypotonic medium, intracellular Ca(2+) store depletion leads to Ca(2+) entry through store-operated Ca(2+) channels. We found it interesting that the activity of the Na(+)/Ca(2+) exchanger measured during this reverse mode operation (Ca(2+) entry in exchange for internal Na(+)) was found to be greatly increased in hypotonic solutions and decreased in hypertonic ones. The buffering of the [Ca(2+)](i) rise induced by hypo-osmotic stress may prevent excessive increases in [Ca(2+)](i), which otherwise might impair the normal function of this glial cell.

Na+ entry via glutamate transporter activates the reverse Na+/Ca2+ exchange and triggers Ca(i)2+-induced Ca2+ release in rat cerebellar Type-1 astrocytes.

We have previously demonstrated that rat cerebellar Type-1 astrocytes express a very active genistein sensitive Na(+)/Ca(2+) exchanger, which accounts for most of the total plasma membrane Ca(2+) fluxes and for the clearance of loads induced by physiological agonists. In this work, we have explored the mechanism by which the reverse Na(+)/Ca(2+) exchange is involved in agonist-induced Ca(2+) signaling in rat cerebellar astrocytes. Microspectrofluorometric measurements of Cai(2+) with Fluo-3 demonstrate that the Cai(2+) signals associated long (> 20 s) periods of reverse operation of the Na(+)/Ca(2+) exchange are amplified by a mechanism compatible with calcium-calcium release, while those associated with short (< 20 s) pulses are not amplified. This was confirmed by pharmacological experiments using ryanodine receptors agonist (4-chloro-m-cresol) and the endoplasmic reticulum ATPase inhibitor (thapsigargin). Confocal microscopy demonstrates a high co-localization of immunofluorescent labeled Na(+)/Ca(2+) exchanger and RyRs. Low (< 50 micromol/L) or high (> 500 micromol/L) concentrations of L-glutamate (L-Glu) or L-aspartate causes a rise in which is completely blocked by the Na(+)/Ca(2+) exchange inhibitors KB-R7943 and SEA0400. The most important novel finding presented in this work is that L-Glu activates the reverse mode of the Na(+)/Ca(2+) exchange by inducing Na(+) entry through the electrogenic Na(+)-Glu-co-transporter and not through the ionophoric L-Glu receptors, as confirmed by pharmacological experiments with specific blockers of the ionophoric L-Glu receptors and the electrogenic Glu transporter.

Role of Na+/Ca2+ exchange in [Ca2+]i clearance in rat culture Purkinje neurons requires reevaluation.

Previous studies have shown that in contrast to other neuronal cells, Na(+)/Ca(2+) exchange contributes little to Ca(i)(2+) homeostasis in rat cerebellar Purkinje neurons under intracellular perfused conditions and at room temperature [Fierro et al.: J Physiol (Lond) 510: 499-512, 1998]. The purpose of this study was to clarify the role of this transporter in cerebellar Purkinje neurons by using intact cells at nearly physiological body temperature. Using Fluo-3 microfluorometry, we have examined the role of the Na(+)/Ca(2+) exchange in the buffering of calcium loads in cultured rat Purkinje neurons at two temperatures: 20 and 34 degrees C. At 20 degrees C, the recovery of the K(+)-induced [Ca(2+)](i) signal was little affected by the presence of external Na(+) (tau(e) = 35.5 +/- 1.2 s [n = 49]), or by its absence (tau(e) = 36.6 +/- 2.2 s [n = 29]), i.e. in a Li(+)-containing medium. In contrast, at 34 degrees C, the recovery of the [Ca(2+)](i) signal was highly dependent on external Na, i.e. tau(e) = 19.9 +/- 1.2 s (n = 119) and tau(e) = 41.7 +/- 2.6 s (n = 39), in Li(+)-containing media, respectively. A comparison of the rate of clearance of [Ca(2+)](i) in Na(+) or Li(+) media, shows that at a room temperature of 20 degrees C, the Na(+)/Ca(2+) exchange contributes at most to 15-20% of the total [Ca(2+)](i) clearance, compared to 55-65% at 34-36 degrees C. We also demonstrate that under normal physiological conditions forward and reverse Na(+)/Ca(2+) exchanges operate in the same neuron. We conclude that the Na(+)/Ca(2+) exchange is strongly suppressed at room temperature and therefore its role should be reevaluated among different neuronal preparations.

Hipercinesia un equivalente epiléptico: beneficio del tratamiento integral / Hiperkinesy a epileptic equivalent: integral of treatment benefit

De un grupo de doscientos setenta y ocho pacientes hiperactivos en el INAPSI, durante los años 1988 a 1992, se tomó una muestra de setenta y cuatro. El tratamiento farmacológico utilizado fue la Difenilhidantoína o la Carbamazepina, por considerar la hiperactividad, trastornos caracteriales (irritabilidad, impulsividad, baja tolerancia a las frustraciones), sueño intranquilo, bruxismo y sonambulismo, un "equivalente epiléptico". Se obtuvo un buen resultado. Desde 1965 el doctor A. Pimentel utiliza estos dos medicamentos y posteriormente el Clonazepán en pacientes adultos con hiperactividad, trastornos caracteriales, del sueño, algunos cuadros depresivos y otros, con resultados igualmente satisfactorios, pareciendo apoyar nuestras observaciones en niños. El tratamiento multidisciplinario consistió en ofrecer simultáneamente el control farmacológico, educación y orientación familiar, psicoterapia grupal, terapia educativa y otras terapias especiales según requerimientos del paciente