Biomedical subjects

R Rodríguez-Puertas

Publications and source records attributed to R Rodríguez-Puertas.

9 recordsLinked to original sources

PubMed2002

Neurotransmitter receptor-mediated activation of G-proteins in brains of suicide victims with mood disorders: selective supersensitivity of alpha(2A)-adrenoceptors.

Abnormalities in the density of neuroreceptors that regulate norepinephrine and serotonin release have been repeatedly reported in brains of suicide victims with mood disorders. Recently, the modulation of the [(35)S]GTPgammaS binding to G-proteins has been introduced as a suitable measure of receptor activity in postmortem human brain. The present study sought to evaluate the function of several G-protein coupled receptors in postmortem brain of suicide victims with mood disorders. Concentration-response curves of the [(35)S]GTPgammaS binding stimulation by selective agonists of alpha(2)-adrenoceptors, 5-HT(1A) serotonin, mu-opioid, GABA(B), and cholinergic muscarinic receptors were performed in frontal cortical membranes from 28 suicide victims with major depression or bipolar disorder and 28 subjects who were matched for gender, age and postmortem delay. The receptor-independent [(35)S]GTPgammaS binding stimulation by mastoparan and the G-protein density were also examined. The alpha(2A)-adrenoceptor-mediated stimulation of [(35)S]GTPgammaS binding with the agonist UK14304 displayed a 4.6-fold greater sensitivity in suicide victims than in controls, without changes in the maximal stimulation. No significant differences were found in parameters of 5-HT(1A) serotonin receptor and other receptor-mediated [(35)S]GTPgammaS binding stimulations. The receptor-independent activation of G-proteins was similar in both groups. Immunoreactive densities of G(alphai1/2)-, G(alphai3)-, G(alphao)-, and G(alphas)-proteins did not differ between suicide victims and controls. In conclusion, alpha(2A)-adrenoceptor sensitivity is increased in the frontal cortex of suicide victims with mood disorders. This receptor supersensitivity is not related to an increased amount or enhanced intrinsic activity of G-proteins. The new finding provides functional support to the involvement of alpha(2)-adrenoceptors in the pathogenesis of mood disorders.

Adult↗

PubMed2000

Characterization of receptor-mediated [35S]GTPgammaS binding to cortical membranes from postmortem human brain.

The [35S]GTPgammaS binding assay represents a functional approach to assess the coupling between receptors and G-proteins. The optimal conditions for [35S]GTPgammaS binding to human brain homogenates were established in postmortem samples of prefrontal cortex. The influence of protein content, incubation time, GDP, Mg(2+), and NaCl concentrations on the [35S]GTPgammaS binding were assessed in the absence and presence of the alpha(2)-adrenoceptor agonist UK14304 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine). In conditions of 50 microM GDP and 100 mM NaCl, UK14304 increased the apparent affinity of the specific [35S]GTPgammaS binding without changing the apparent density. Concentration-response curves to agonists of alpha(2)-adrenoceptors, mu-opioid, 5-HT(1A), cholinergic muscarinic, and GABA(B) receptors displayed, in the presence of NaCl, maximal stimulations between 24% and 61% with EC(50) values in the micromolar range. Selective antagonists shifted to the right the agonist-induced stimulation curves. The G(i)/G(o)-protein alkylating agent N-ethylmaleimide decreased basal [35S]GTPgammaS binding in a concentration-dependent manner and inhibited the stimulation induced by the different agonists. In cortical sections, [35S]GTPgammaS binding to gray matter was stimulated by the agonist UK14304. The present study demonstrates that functional studies of the receptor coupling to G(i)/G(o)-proteins can be performed in postmortem human brain samples.

Adrenergic alpha-2 Receptor Agonists↗

PubMed2000

Autoradiography of receptor-activated G-proteins in post mortem human brain.

The agonist-stimulated guanosine 5'-(gamma-[(35)S]thio)triphosphate binding assay was used to anatomically localize receptor-activated G-proteins by autoradiography in post mortem human brain. The optimal conditions for guanosine 5'-(gamma-[(35)S]thio)triphosphate binding to human brain sections were established in post mortem samples of the prefrontal cortex, hippocampus, basal ganglia, brainstem and cerebellar cortex. An excess of GDP (2mM) was required to decrease basal activity and obtain effective stimulation by specific agonists. guanosine 5'-(gamma-[(35)S]Thio)triphosphate binding was increased after stimulation with specific agonists of different G-protein-coupled receptors. They include cannabinoid (WIN55212-2), mu-opioid ([D-Ala(2),N-Me-Phe(4), Gly(5)-ol]enkephalin), serotonin-1A [(+/-)-8-hydroxy-2-(di-n-propylamino)tetralin] and serotonin-1B/1D (sumatriptan), cholinergic muscarinic receptors (carbachol) and alpha(2)-adrenoceptors (UK14304). Such stimulation reached 1458%, 440%, 188%, 219%, 61% and 339%, respectively, over the basal levels. In tissue sections, the use of the above-mentioned agonists (10(-4)M) showed patterns of anatomical distribution similar to those already described by receptor autoradiography, with high densities over the hippocampus (serotonin-1A receptors), cortex (alpha(2)-adrenoceptors) and striatum (mu-opioid receptors). The highest binding levels were reached with the cannabinoid receptor agonist in most of the analysed brain regions. Carbachol produced only moderate stimulation of those same regions. The blockage of agonist-stimulated guanosine 5'-(gamma-[(35)S]thio)triphosphate binding by selective antagonists verified that the effect was receptor mediated. This technique provides a method to identify modifications of the receptor-mediated activation of G-proteins in post mortem human brain with anatomical resolution. It also provides valuable information on the level of drug efficacy in the human species.

Adult↗

PubMed1999

Dopamine D1 receptor modulation of glutamate receptor messenger RNA levels in the neocortex and neostriatum of unilaterally 6-hydroxydopamine-lesioned rats.

The effect of treatment with the D1 dopamine receptor agonist SKF 38393 on the expression of metabotropic glutamate receptor 1, 3, 4 and 5 receptor subtypes and of the glutamate N-methyl-D-aspartate ionotropic receptor subunits NRI, NR2A and NR2B was analysed using in situ hybridization. We studied the neocortex and neostriatum of normal rats and of rats unilaterally treated with 6-hydroxydopamine, a neurotoxin that, after intracerebral injection into the ventral tegmental area, causes selective degeneration of the ascending dopamine pathway. In the 6-hydroxydopamine-lesioned rats, metabotropic glutamate receptor subtype 3 messenger RNA levels were ipsilaterally increased in the neocortex and neostriatum, while the levels of metabotropic glutamate receptor subtype 4 messenger RNA were bilaterally increased in both regions. When administered to the 6-hydroxydopamine-lesioned rats, the D1 receptor agonist SKF 38393 (3 x 20 mg/kg, s.c.) produced a bilateral decrease in the expression of the metabotropic glutamate receptor subtype 1 and 5 receptor messenger RNA levels in the neocortex and neostriatum. In the neostriatum, SKF 38393 attenuated the ipsilateral increase in the expression of striatal metabotropic glutamate receptor subtype 3 messenger RNA produced by the 6-hydroxydopamine lesion. Furthermore, SKF 38393 produced a bilateral decrease in the levels of NRI receptor subunit messenger RNA and, in contrast, an increase in the striatal NR2B messenger RNA levels. All of these effects were abolished by the D1 receptor antagonist SCH 23360. These results indicate a differential D1 receptor-mediated modulation of the expression of some glutamate receptor subtypes in the neostriatum and neocortex, in agreement with the idea of a functional coupling between dopamine and excitatory amino acid systems in both regions. Thus, pharmacological targeting of excitatory amino acid systems could provide alternative or complementary treatment strategies for diseases involving dopaminergic systems in the striatum (e.g., Parkinson's disease) and cortex (e.g., schizophrenia).

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1997

Autoradiographic distribution of M1, M2, M3, and M4 muscarinic receptor subtypes in Alzheimer's disease.

We studied the autoradiographic densities of all pharmacologically characterised muscarinic receptors (MR) in frontal, temporal, and visual cortex, hippocampal formation, and striatum in autopsied brains from 19 histopathologically verified patients of Alzheimer's disease (AD) and in matched controls. Almost all (16 of 19) of the AD cases were severe. In AD brains, total MR, M1, and M3 MR subtypes were found to be significantly decreased in entorhinal cortex and in most hippocampal strata. Total MR and M1 receptors were also significantly reduced in visual area and in frontal cortex of AD brains, respectively. M2 receptors were significantly reduced over hippocampal formation but increased significantly in striatum of AD brains as compared with controls. M3 receptors in AD were in the range of controls in neocortex and striatum, whereas the M4 receptor subtype was also preserved in all brain regions in AD brains when compared with controls. This is the first autoradiographic study analysing the distribution of all MR subtypes in AD brains. These changes in MR densities concur with the general pattern of neuronal degeneration occurring in AD brains and partly explain the poor response of AD cognitive decline to present cholinergic supplementation therapies. Although M3 and M4 MR were labelled with nonselective approaches, the preservation of M4 and to a lesser degree M3 MR subtypes in AD brains could open an alternative way for the symptomatic therapy of AD dementia.

Aged↗

PubMed1997

125I-galanin binding sites in Alzheimer's disease: increases in hippocampal subfields and a decrease in the caudate nucleus.

Using iodinated human galanin and autoradiography, galanin binding sites were studied in cortical and hippocampal areas and in some brainstem nuclei in the brains of eight patients with senile dementia of the Alzheimer type (SDAT) and of nine matched control cases. The highest density of binding sites was found in the substantia nigra with a less intense labeling in the hippocampus and cortical regions. In the SDAT cases a significant increase in number of galanin binding sites was found in some hippocampal areas, a decrease in the caudate nucleus, and no significant changes in frontal and entorhinal cortices. These findings suggest that some central galanin systems may be deranged in SDAT.

Aged↗

PubMed1994

Cholinergic markers in degenerative parkinsonism: autoradiographic demonstration of high-affinity choline uptake carrier hyperactivity.

[3H]Hemicholinium-3 ([3H]HC-3) binding, as a marker of the presynaptic high-affinity choline uptake carrier (HACU), and cholinergic muscarinic receptors were measured by autoradiography in several brain regions of levodopa-responsive parkinsonism and matched cases. A significant increase in the density of [3H]HC-3 binding sites was found in the striatum of parkinsonian brains, while there was a slight decrease in the parkinsonian hippocampus. Total, M1 and non-M1 muscarinic receptors remained unchanged in frontal cortex and striatum of parkinsonian brains as compared to controls. Total and non-M1 muscarinic receptors were significantly reduced in the parkinsonian hippocampus, whereas hippocampal M1 receptors were preserved. These data demonstrate a hyperactivity of the HACU, and thus of the acetylcholine synthesis, in parkinsonian brains probably compensatory of the loss of both dopaminergic terminals in the striatum and of basal forebrain neurons in the hippocampus. Our results emphasize the value of [3H]HC-3 binding in the study of the functional status of the cholinergic synapse in neurodegenerative disorders.

Aged↗

PubMed1994

Selective cortical decrease of high-affinity choline uptake carrier in Alzheimer's disease: an autoradiographic study using 3H-hemicholinium-3.

3H-hemicholinium-3 (3H-HC-3) binding, a marker of the presynaptic high-affinity choline uptake carrier (HACU), was measured by autoradiography in several brain regions of 17 Alzheimer's disease (AD) patients and of 11 matched controls. A significant decrease in the density of 3H-HC-3 binding sites was found in entorhinal cortex, hippocampus and layers I-III of the frontal cortex. By contrast, in the caudate-putamen the number of 3H-HC-3 binding sites in AD cases was comparable to that of control striata. These data concur with previous results using classical presynaptic markers and reflect the loss in the activity of HACU, and, hence, in the synthesis of acetylcholine, that selectively occurs in cortical areas of AD brains due to the degeneration of presynaptic cholinergic terminals arising from the basal forebrain. However, the relatively low mean reduction in HACU in cortical areas (-40%), together with the apparent indemnity of this marker in certain severely demented AD cases, suggest that AD dementia cannot be explained simply by the loss of presynaptic terminals originating in the basal forebrain. These data seem to be a good explanation for the poor response to cholinergic replacement in AD.

Aged↗

PubMedDate not supplied

Regional and subcellular distribution of soluble aminopeptidase in the human and the rat brain: a comparative study.

In an attempt to elucidate the cellular function of the soluble aminopeptidases, we have analysed their activity in several subcellular fractions (synaptosomal, mitochondrial, microsomal, nuclear and cytosolic fraction) and in different areas (amygdala, hypothalamus, hippocampus, striatum, frontal cortex, occipital cortex and parietal cortex) of the human and the rat brain. The enzymes assayed in this study were five cytosolic aminopeptidases identified inmammalian brain tissues: alanyl-aminopeptidase, arginyl-aminopeptidase, leucyl-aminopeptidase, pyroglutamyl-peptidase I and aspartyl-aminopeptidase. The regional comparative study revealed significantly higher activities of alanyl-aminopeptidase activity in the human brain, with arginyl-aminopeptidase activities being higher in the rat brain. In the subcellular study, while the alanyl- and arginyl-aminopeptidase activities were quite homogeneous in all the subcellular fractions, the leucyl-aminopeptidase, pyroglutamyl-peptidase I and aspartyl-aminopeptidase activities were significantly higher in the synaptosomal fraction. The differential distribution of these enzymes could suggest that these activities have different functions in the distinct subcellular structures of the human and the rat brain.

Aminopeptidases↗