Longitudinal studies of ischemic penumbra by using 18F-FDG PET and MRI techniques in permanent and transient focal cerebral ischemia in rats.

At present, the goal of stroke research is the identification of a potential recoverable tissue surrounding the ischemic core, suggested as ischemic penumbra, with the aim of applying a treatment that attenuates the growth of this area. Our purpose was to determine whether a combination of imaging techniques, including (18)F-FDG PET and MRI could identify the penumbra area. Longitudinal studies of (18)F-FDG PET and MRI were performed in rats 3 h, 24 h and 48 h after the onset of ischemia. A transient and a permanent model of focal cerebral ischemia were performed. Regions of interest were located, covering the ischemic core, the border that progresses to infarction (recruited tissue), and the border that recovers (recoverable tissue) with early reperfusion. Analyses show that permanent ischemia produces severe damage, whereas the transient ischemia model does not produce clear damage in ADC maps at the earliest time studied. The only significant differences between values for recoverable tissue, (18)F-FDG (84±2%), ADC (108±5%) and PWI (70±8%), and recruited tissue, (18)F-FDG (77±3%), ADC (109±4%) and PWI (77±4%), are shown in (18)F-FDG ratios. We also show that recoverable tissue values are different from those in non-infarcted tissue. The combination of (18)F-FDG PET, ADC and PWI MRI is useful for identification of ischemic penumbra, with (18)F-FDG PET being the most sensitive approach to its study at early times after stroke, when a clear DWI deficit is not observed.

"Full moon" endoscopic sign in intraventricular neurocysticercosis.

INTRODUCTION: Despite improvements in sanitation, diagnosis and treatment, neurocysticercosis is still a public health problem in many countries. In symptomatic patients, there is a broad spectrum of clinical manifestations. When cysticerci are lodged in the ventricles or the subarachnoid space, the flow of cerebrospinal fluid can be obstructed and lead to hydrocephalus and intracranial hypertension. The endoscopic view may be useful as a diagnostic tool. PATIENTS: This report clearly shows a common endoscopic pattern in 4 selected patients with ventricular cysticercosis (2 third ventricle/2 lateral ventricle). The endoscopic view of the cysts in the ventricles resembles a "full moon". This analogy helped to identify the features of cysticerci with intact walls and the vesicular stage, malleable due to its cystic content and having an irregular surface, as evidence of the microscopic structure of the cyst wall in a cysticercus. CONCLUSIONS: This finding is not seen in other intraventricular cysts or tumors that can actually be considered as an additional diagnostic criterion among the definitive findings to establish the diagnosis of cysticercosis, since it involves direct endoscopic visualization of a cysticercus under histopathological demonstration. Additionally, the endoscopic approach can be used as primary treatment for these cases, following the minimally invasive approach principle.

Switch from facilitation to inhibition of excitatory synaptic transmission by group I mGluR desensitization.

We have explored whether the desensitization of metabotropic glutamate receptors (mGluRs) coupled to phosphoinositide hydrolysis affects the role that they play in modulating glutamate release. In hippocampal nerve terminals, the agonist 3,5-dihydroxyphenylglycine (DHPG) facilitated evoked glutamate release, but a second stimulation 5 min later reduced rather than facilitated release. After a 30 min interval between stimulations, DHPG again facilitated glutamate release. In hippocampal slices, DHPG caused an inhibition of excitatory postsynaptic currents (EPSCs) recorded from CA1 neurons. However, when the effects of ambient glutamate were prevented, mGluR activation initially induced a facilitation of synaptic transmission, followed by an inhibition. We conclude that group I mGluRs have a dual action on glutamate release, switching from facilitatory to inhibitory upon receptor desensitization triggered by low concentrations of glutamate.

[Control of blood pressure by using an intelligent telephone application with feedback and competitiveness strategy. HTApp Control project]. / Control de la presión arterial mediante el uso de una aplicación para teléfono inteligente con estrategia de retroalimentación y competitividad. Proyecto Control HTApp.

INTRODUCTION AND OBJECTIVE: Arterial hypertension is a highly important cardiovascular risk factor, with low control percentages. New technologies can help to obtain a better control of this disease. The intention is to know if a mobile application can help achieve this goal. METHOD: A mobile phone application is used to give feedback to physicians with the aim of generate competitiveness in achieving objectives. The application could, at any time, determine the rate of controlled patients (<140/90mmHg) by each physician, and compare them with the mean number of the patients controlled by the group. The possible changes in the therapeutic attitude of physicians are also analysed and the differences in achieving objectives are compared based on specific characteristics of patients. RESULTS: The study included 220 patients aged 18-80 years, with mean blood pressure>140/90mmHg, despite medical treatment, tracked for 4 visits. At the end of the follow-up, 69.03% achieved good control, compared to 12.8% in the baseline study (P<.001), with no differences between gender (control of 68.6 and 69.29% of women and men, respectively), nor among the different levels of cardiovascular risk. CONCLUSIONS: The use of interactive tools that allow the dynamic process of feedback on the results fosters the motivation and improves the therapeutic inertia in the control of blood pressure.

Presynaptic receptors and the control of glutamate exocytosis.

When a typical glutamate-containing neurone fires, an action potential is propagated down the branching axon through more than a thousand varicosities. At each of these release sites the probability that a synaptic vesicle will be exocytosed into the synaptic cleft is individually controlled by means of presynaptic receptors: autoreceptors responding by positive or negative feedback to previously released transmitter, or heteroreceptors under the influence of other neurotransmitters or modulators. The simplest system in which to investigate presynaptic modulation is the isolated nerve terminal or synaptosome; studies with this preparation have revealed a complex interplay of signal-transduction pathways.

Influence of the conformational state on the isoelectric points of rat brain synaptosomes, mitochondria and mitoplasts.

The isoelectric points of rat brain synaptosomes, mitochondria and mitoplasts have been determined by using different charged two-phase systems containing dextran and poly(ethylene glycol). The cross-partition diagrams of these organelles show isoelectric points at pH 4.1, 4.5 and 4.7, respectively. The influence of the conformational state of mitochondrial membranes upon their partition in two-phase systems has been studied. Shrunk mitoplasts showed a large change in their partition behavior as reflected by an increased affinity for the lower dextran phase, while shrinkage of mitochondria did not affect their partition. Shrunk mitoplasts showed the same isoelectric point of pH 4.7 as swollen mitoplasts, which indicates that no charge changes occurred on the outer side of the inner mitochondrial membrane during shrinkage of mitoplasts.

Phorbol ester translocation of protein kinase C in guinea-pig synaptosomes and the potentiation of calcium-dependent glutamate release.

The distribution of protein kinase C activity and specific phorbol ester binding sites between soluble and particulate fractions of isolated guinea-pig cerebral cortical synaptosomes is examined following preincubation with phorbol esters. Half-maximal decrease in cytosolic activity requires 10 nM 4 beta-phorbol myristoyl acetate. Specific [3H]phorbol dibutyrate binding sites are translocated from cytoplasmic to particulate fractions in parallel with protein kinase C activity. Depolarization of the plasma membrane by 30 mM KCl does not cause translocation of protein kinase C. 1 microM 4 beta-phorbol myristoyl acetate and 1 microM 4 beta-phorbol didecanoate (but not 1 microM 4 alpha-phorbol didecanoate) enhance the release of glutamate from synaptosomes partially depolarized by 10 mM KCl; however, 4 beta-phorbol myristoyl acetate is ineffective at 20 nM. 1 microM 4 beta-phorbol myristoyl acetate slightly increases the cytosolic free Ca2+ concentration of polarized synaptosomes, but not that following partial depolarization. 4 beta-Phorbol myristoyl acetate causes a concentration-dependent increase in the Ca2+-dependent glutamate release induced by sub-optimal ionomycin concentrations, but is without effect on the release induced by maximal ionomycin. It is concluded that phorbol esters stereospecifically enhance the Ca2+-sensitivity of glutamate release, but that higher concentrations may be required than for protein kinase C translocation in the same preparation. Instead the enhancement may be related to the rapid inactivation of protein kinase C which occurs with phorbol esters.

Inhibition of N- and P/Q-type Ca2+ channels by cannabinoid receptors in single cerebrocortical nerve terminals.

Since cannabinoid receptors inhibit excitatory synaptic transmission by reducing glutamate release, we have examined whether this might occur through the direct inhibition of presynaptic Ca2+ channels. In cerebrocortical nerve terminals, activation of cannabinoid receptors with WIN55,212-2 reduces the KCl-evoked release of glutamate. However, this inhibition is attenuated when N- and P/Q-type Ca2+ channels are blocked. Through Ca2+ imaging in single nerve terminals, we found that WIN55,212-2 reduced the influx of Ca2+ both in nerve terminals that contain N-type Ca2+ channels and those that contain P/Q-type Ca2+ channels. Thus, cannabinoid receptors modulate the two major Ca2+ channels coupled to glutamate release in the cerebral cortex.

Dual signaling by mGluR5a results in bi-directional modulation of N-type Ca2+ channels.

We have studied how N-type Ca2+ channels are modulated by the metabotropic glutamate receptor 5a (mGluR5a) in Xenopus oocytes. Stimulation of the receptor with glutamate initiated two parallel responses, a rapid inhibition followed by an upregulation of the Ca2+ current. Although a subsequent stimulation did not upregulate the Ca2+ current, it did still produce a reduction in the amplitude of the current. The upregulation of Ca2+ channels was prevented by the protein kinases inhibitor staurosporine and it was mimicked by the activation of PKC with phorbol esters. In contrast, the inhibition of the Ca2+ current was insensitive to staurosporine. These results show that mGluR5a exerts a bi-directional influence on Ca2+ channels, which may explain how group I mGluRs facilitate and inhibit glutamate release at central synapses.

PKC-independent inhibition of glutamate exocytosis by arachidonic acid in rat cerebrocortical synaptosomes.

In rat cerebrocortical synaptosomes, the addition of 4 beta-phorbol dibutyrate (4 beta-PDBu) and arachidonic acid enhances and decreases, respectively, the glutamate release evoked by 4-aminopyridine. Pretreatment of synaptosomes with 12-O-tetradecanoylphorbol 13-acetate (TPA) or pre-incubation with staurosporine, prevent the stimulatory effect of 4 beta-PDBu, but are without effect on the inhibitory action of arachidonic acid. Moreover, methyl arachidonate, which is not effective as a PKC activator, also strongly inhibits glutamate exocytosis. These results suggest that PKC is not involved in the inhibition of glutamate release by arachidonic acid.

Protein phosphatase 2B inhibitors mimic the action of arachidonic acid and prolong the facilitation of glutamate release by group I mGlu receptors.

We have addressed the role of arachidonic acid in the facilitation of glutamate release by group I metabotropic glutamate (mGlu) receptors. The activation of these receptors with the specific agonist 3,5-dihydroxyphenylglycine (DHPG) failed to enhance the cumulative Ca(2+)-dependent release of glutamate evoked by a 5 min depolarization with 4-aminopyridine, in the absence but not in the presence of arachidonic acid. However, DHPG, in the absence of arachidonic acid, transiently enhanced diacylglycerol levels, transiently potentiated 4AP-evoked depolarization, and significantly enhanced the fast but not the slow component of glutamate release observed after prolonged stimulations of nerve terminals. Further evidence that DHPG was able to initiate release facilitation in the absence of arachidonic acid was obtained in experiments where the protein phosphatase 2B (cyclosporine A and cypermethrine) but not protein phosphatase 1 or 2A inhibitors (okadaic acid and calyculin A) facilited glutamate release to a maximal extent comparable to that induced by arachidonic acid. We conclude that an active protein phosphatase 2B (calcineurin) dephosphorylates the presynaptic target/s responsible for facilitation of glutamate release.

The metabotropic glutamate receptor 1 is not involved in the facilitation of glutamate release in cerebrocortical nerve terminals.

In this study we have addressed the identification of the metabotropic glutamate receptor (mGluR) involved in the facilitation of glutamate release in nerve terminals from the cerebral cortex. mGluR1 and 5 are coupled to phosphoinositide hydrolysis and the activation of these receptors with the specific agonist 3,5-dihydroxyphenylglycine (DHPG) enhances the release of glutamate. We have examined whether mGluR1 is responsible for this modulatory effect by preparing nerve terminals from mGluR 1 deficient mice. The Ca2+-dependent glutamate release evoked by a submaximal depolarization is enhanced by the agonist DHPG in nerve terminals from both wild and mutant mice. This result is consistent with the finding that the mGluR agonist also induces a similar increase in the levels of diacylglycerol (DAG) in the nerve terminals from wild and mutant mice. Moreover, the activity-dependent switch from facilitation to inhibition of release, observed when a second stimulation of the receptor is applied shortly after (5 min) the first pulse, was also observed in the mutant mice. These results indicate therefore, that the facilitation of glutamate release is unlikely to be due to the activation of mGluR1 but related to another phosphoinositide coupled mGluR.

Co-existence and interaction between facilitatory and inhibitory metabotropic glutamate receptors and the inhibitory adenosine A1 receptor in cerebrocortical nerve terminals.

We have investigated the interaction between facilitatory and inhibitory metabotropic glutamate receptors (mGluRs) and the inhibitory adenosine A1 receptor in cerebrocortical nerve terminals from young (3 weeks postnatal) rats. The adenosine A1 receptor agonist N6-cyclohexyladenosine (CHA) (1 microM) and the mGluR agonist L-2-amino-4-phosphonobutyrate (L-AP4) (100 microM) inhibited Ca(2+)-dependent release of glutamate evoked by depolarization of synaptosomes with 30 mM KCl to 33 +/- 6 and 30 +/- 4% of control values, respectively. The CHA and L-AP4 inhibition of release was consistent with the reduction of a component of Ca2+ entry in nerve terminals which was also sensitive to omega-Aga-IVA. When the inhibitory agonists were co-applied at optimal concentrations, no additivity of the inhibitory effects on either glutamate release or [Ca2+]c was observed. The nerve terminals from young rats also exhibit the facilitatory pathway for glutamate release that is observed during 4-aminopyridine-evoked depolarization after stimulation of mGluRs with the agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate (ACPD) in the presence of arachidonic acid (AA). The addition of ACPD or AA alone did not alter the ability of CHA and L-AP4 to reduce the release, however the co-application of AA and ACPD abolished the inhibitory effect induced by CHA and L-AP4 whether alone or in combination. These results indicate the co-existence of the three modulatory pathways of glutamate release and the dominant role of the ACPD/AA activated facilitatory pathway in its interaction with the inhibitory pathways activated by L-AP4 and CHA.

Group-I metabotropic glutamate receptors: hypotheses to explain their dual role in neurotoxicity and neuroprotection.

The role of group-I metabotropic glutamate receptors (mGlu1 and 5) in neurodegeneration is still controversial. While antagonists of these receptors are consistently neuroprotective, agonists have been found to either amplify or attenuate excitotoxic neuronal death. At least three variables affect responses to agonists: (i) the presence of the NR2C subunit in the NMDA receptor complex; (ii) the existence of an activity-dependent functional switch of group-I mGlu receptors, similar to that described for the regulation of glutamate release; and (iii) the presence of astrocytes expressing mGlu5 receptors. Thus, a number of factors, including the heteromeric composition of NMDA receptors, the exposure time to drugs or to ambient glutamate, and the function of astrocytes clearing extracellular glutamate and producing neurotoxic or neuroprotective factors, must be taken into account when examining the role of group-I mGlu receptors in neurodegeneration/neuroprotection.

Presynaptic group 1 metabotropic glutamate receptors may contribute to the expression of long-term potentiation in the hippocampal CA1 region.

In this study, we investigated the possible contribution of presynaptic group 1 metabotropic glutamate receptor activation to changes in synaptic efficacy by means of analysis of glutamate release in hippocampal synaptosomes. Data were interpreted in the context of group 1 metabotropic glutamate receptor involvement in synaptic plasticity in the CA1 region of freely moving rats. In synaptosomes, 3,5-dihydroxyphenylglycine enhanced diacylglycerol formation and facilitated vesicular Ca(2+)-dependent glutamate release, whereas trans-azetidine-2,4-dicarboxylic acid had no effect on these processes. Trans-azetidine-2,4-dicarboxylic acid enhanced glutamate release, but in a Ca(2+)-independent manner. This effect was mimicked by the L-glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid. (R,S)-alpha-Methyl-4-carboxyphenylglycine blocked the effects of 3,5-dihydroxyphenylglycine, but not trans-azetidine-2,4-dicarboxylic acid in synaptosomes. Short-term potentiation (100 Hz, three bursts of 10 stimuli, 0.1 ms stimulus duration, 10 s interburst interval) was induced in the CA1 region in vivo. The metabotropic glutamate receptor agonist 1S,3R-aminocyclopentane-2,3-dicarboxylic acid, or the group 1 metabotropic glutamate receptor agonists, 3,5-dihydroxyphenylglycine and trans-azetidine-2,4-dicarboxylic acid, dose-dependently facilitated short-term potentiation into long-term potentiation, which lasted > 24 h. The facilitation was inhibited by the metabotropic glutamate receptor antagonist, (R,S)-alpha-methyl-4-carboxyphenylglycine, and the group 1 metabotropic glutamate receptor antagonist, (S)-4-carboxy-phenylglycine, but not by the group 2 metabotropic glutamate receptor antagonist, (R,S)-alpha-methylserine-O-phosphate monophenyl ester. L-Trans-pyrrolidine-2,4-dicarboxylic acid dose-dependently facilitated short-term potentiation into long-term potentiation, which lasted < 4 h. These data suggest that activation of group 1 metabotropic glutamate receptors results in presynaptic modulation of glutamate release. This effect may contribute to group 1 metabotropic glutamate modulation of the expression of long-term potentiation in vivo.

Developmental change from inhibition to facilitation in the presynaptic control of glutamate exocytosis by metabotropic glutamate receptors.

We have addressed the role of presynaptic metabotropic glutamate receptors in the control of glutamate release from cerebrocortical nerve terminals. The metabotropic glutamate receptor agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid enhances the release evoked by a submaximal depolarization in the presence of low concentrations of arachidonic acid and in a staurosporine-sensitive manner. In contrast, (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid and L(+)-2-amino-4-phosphonobutyrate inhibit the release evoked by a maximal depolarization, in the absence of arachidonic acid and by a staurosporine-insensitive mechanism. Interestingly, the effects of the metabotropic glutamate receptors that inhibit glutamate release are only observed in the nerve terminals from young rats (one to three weeks), while the facilitatory effects are better seen in latter developmental stages (three to four weeks) and adult (two to three months) rats, coinciding with the development of the maximal capacity of glutamate uptake. These results indicate the existence of important developmental changes in the presynaptic control of glutamate release.

Modulation of glutamate release by a nitric oxide/cyclic GMP-dependent pathway.

The mechanism by which changes in cyclic GMP (cGMP) regulate glutamate release was investigated in rat cerebrocortical nerve terminals. The elevation of cGMP levels by inhibition of cGMP-phosphodiesterase with 2-o-propoxy-phenyl-8-azapurin-6-one (zaprinast) reduced the Ca(2+)-dependent glutamate release evoked by depolarization with 30 mM KCl or 1 mM 4-aminopyridine. The nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine also enhanced cGMP and reduced glutamate release. In addition, the membrane-permeable analogs 8-bromoguanosine 3':5'-cyclic monophosphate (8-Br-cGMP) and N,2'-o-dibutyrylguanosine (dbcGMP) at 10 microM also mimic glutamate release inhibition. The reduction in glutamate release was observed with no modifications in the ATP/ADP ratio, and was reversed in the presence of the protein kinases inhibitor [N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide, HCl] (H-8). Interestingly, higher concentrations of dbcGMP (1 mM) abolished the inhibition observed with low concentrations although no facilitation was observed. This finding seems to indicate the existence of a dual role for cGMP in the control of glutamate exocytosis.

Role of arachidonic acid in the facilitation of glutamate release from rat cerebrocortical synaptosomes independent of metabotropic glutamate receptor responses.

The role of arachidonic acid in the facilitation of glutamate release by the metabotropic glutamate receptor, mGluR, agonist (1S,3R)-1-amino-cyclo-pentane-1,3-dicarboxylate ((1S,3R)-ACP), was investigated in cerebrocortical nerve terminals from adult rats. mGluR activation with the agonist (1S,3R)-ACPD involved a transient increase in the intrasynaptosomal concentration of diacylglycerol that was not altered by the presence of arachidonic acid either in polarized synaptosomes, or in synaptosomes depolarized with 4-aminopyridine. These results suggest that the locus of the arachidonic acid action in the facilitation of glutamate release is downstream of the metabotropic glutamate receptor in the signal transduction pathway.

Glutamate exocytosis evoked by 4-aminopyridine is inhibited by free fatty acids released from rat cerebrocortical synaptosomes.

The Ca(2+)-dependent release of glutamate induced by 4-aminopyridine (4-AP) in rat cerebral cortical synaptosomes was reduced by removal of bovine serum albumin (BSA) from the incubation medium. The decrease in the glutamate release in the absence of BSA was consistent with a reduction in the rise in cytosolic free [Ca2+] after depolarization with 4-AP. Contrarily, neither the glutamate release nor the elevation in cytosolic free [Ca2+] after depolarization with 30 mM KCl was altered by the removal of BSA. The inhibitory action of the free fatty acids released during the incubation of synaptosomes was also observed when exogenous free fatty acids were added to the medium in the presence of BSA. The highest inhibition of 4-AP-induced release of glutamate was observed in the presence of arachidonic acid. The results strongly suggest an inhibitory action of free fatty acids by decreasing Ca2+ entry and glutamate release in rat cerebrocortical synaptosomes.

Unchanged exocytotic release of glutamic acid in cortex and neostriatum of the rat during aging.

The Ca(2+)-dependent release of glutamate induced by 4-aminopyridine in synaptosomes prepared both from the cerebral cortex and basal ganglia was unchanged in aged rats (27-30 months) when compared to adults rats (3 months). Consistent with the absence of changes in glutamate exocytosis during aging, the rise in the cytosolic free Ca2+ concentration, [Ca2+]c, induced by depolarization in synaptosomes from aged rats was similar to that found in control adult rats. The results suggest that during aging the nerve terminals from the cerebral cortex and basal ganglia maintain an intact ability to release glutamate by exocytosis.