Biomedical subjects

Angel Pazos

Publications and source records attributed to Angel Pazos.

14 recordsLinked to original sources

PubMed2006

In vitro and in vivo characterization of F-97013-GD, a partial 5-HT1A agonist with antipsychotic- and antiparkinsonian-like properties.

In order to better define the role of 5-HT(1A) receptors in the modulation of extrapyramidal motor functions, we investigated the effect of 5-HT(1A) agonists on tacrine-induced tremulous jaw movements (TJM) in rats, a putative model of parkinsonian tremor. Acute injection of 5-HT(1A) agonists 8-OH-DPAT and buspirone dose-dependently counteracted the tacrine-induced oral movements (ED(50)=0.04 and 1.0mg/kg, respectively), an effect reversed by the selective 5-HT(1A) antagonist WAY 100,635. In contrast to classical antipsychotics, the atypical antipsychotics risperidone (ED(50)=0.3mg/kg) and clozapine (ED(50)=1.5mg/kg) blocked the oral movements induced by the cholinomimetic agent at or below the doses required for suppression of conditioned avoidance response. The compound F-97013-GD (6-methyl-2-[4-(naphtylpiperazin-1-yl)butyl]-3-(2H)-pyridazinone), a putative antipsychotic drug that in functional in vitro and in vivo assays behaved as a mixed dopamine D(2)-antagonist and 5-HT(1A)-partial agonist, also displayed a potent antitremorgenic effect in this paradigm (ED(50)=0.5mg/kg). Interestingly, pretreatment with WAY 100,635 blocked the inhibitory effect of F-97013-GD but not that of clozapine. The 5-HT depleting agent para-chlorophenylalanine (PCPA) partially attenuated tacrine-induced TJM but did not block the suppressive effect of 5-HT(1A) agonists. In addition, only high doses of F-97013-GD induced catalepsy in rodents and, like 8-OH-DPAT and clozapine, the compound reversed the haloperidol-induced catalepsy in rats. These results show that 5-HT(1A) receptors play a role in the regulation of tacrine-induced TJM and suggest that their activation by novel antipsychotics may not only reduce the extrapyramidal side effects EPS liability, but also be effective in the treatment of parkinsonian tremor.

5-Hydroxytryptophan↗

PubMed2006

Transmembrane signaling through phospholipase C-beta in the developing human prefrontal cortex.

To investigate changes in muscarinic receptor-stimulated phospholipase C-beta (PLC-beta) activity during brain development, we examined the functional coupling of each of the three major protein components of the phosphoinositide system (M1, M3, and M5 muscarinic receptor subtypes; Gq/11 proteins; PLC-beta1-4 isoforms) in membrane preparations from post-mortem human prefrontal cerebral cortex collected at several stages of prenatal and postnatal development. In human prenatal brain membranes, PLC was found to be present and could be activated by calcium, but the ability of guanosine-5'-o-3 thiotriphosphate (GTPgammaS) or carbachol (in the presence of GTPgammaS) to modulate prenatal PLC-beta was significantly weaker than that associated with postnatal PLC-beta. Western blot analysis revealed that the levels of Galphaq/11 did not change significantly during development. In contrast, dramatically higher levels of expression of PLC-beta1-4 isoforms and of M1, M3, and M5 muscarinic receptors were detected in the child vs. the fetal brain, a finding that might underlie the observed increased activity of PLC. Thus, inositol phosphate production may be more efficiently regulated by altering the amount of effectors (PLC-beta1-4) and receptors (M1,3,5 subtypes) than by altering the level of Galphaq/11 subunits. These results demonstrate that different PLC isoforms are expressed in the prefrontal cortex of the developing human brain in an age-specific manner, suggesting specific roles not only in synaptic transmission but also in the differentiation and maturation of neurons in the developing brain.

Actins↗

PubMed2005

Preclinical pharmacology of F-98214-TA, a novel potent serotonin and norepinephrine uptake inhibitor with antidepressant and anxiolytic properties.

RATIONALE: Serotonin (5-HT) and norepinephrine (NE) re-uptake inhibitors (SNRIs) have been proposed to have a higher efficacy and/or faster onset of action than previously available antidepressants. OBJECTIVES: We examined in biochemical, electrophysiological and behavioural assays the antidepressant properties of (S)-(-)-4-[(3-fluorophenoxy)-phenyl]methyl-piperidine (F-98214-TA), a compound that displays very high affinity for 5-HT and NE transporters. RESULTS: F-98214-TA potently inhibited the uptake of both 5-HT and NE into rat brain synaptosomes (IC50 = 1.9 and 11.2 nM, respectively) and decreased the electrical activity of dorsal raphe serotonergic neurones (ED50 = 530.3 microg/kg i.v.), an effect completely abolished by the 5-HT(1A) antagonist WAY100,635. In acute behavioural assays in mice, the orally administered compound potentiated the 5-hydroxy-tryptophan (5-HTP)-induced syndrome [minimal effective dose (MED) = 10 mg/kg], antagonized the hypothermia induced by a high dose of apomorphine (ED50 = 2 mg/kg) and reduced the immobility in the tail suspension test (MED = 10 mg/kg). Moreover, it also decreased the immobility in the forced swimming test in mice and rats (30 mg/kg, p.o.). Chronic administration of F-98214-TA (14 days, 30 mg kg(-1) day(-1), p.o.) attenuated the hyperactivity induced by olfactory bulbectomy in rats, confirming its antidepressant-like properties. Interestingly, the same dosage regimen significantly increased the social interaction time in rats, suggesting an additional potential anxiolytic activity. In most assays the compound was more potent than fluoxetine, venlafaxine and desipramine. CONCLUSIONS: F-98214-TA is a novel SNRI that displays greater potency than other reference antidepressants in animal models predictive of antidepressant and anxiolytic activities.

Adrenergic Uptake Inhibitors↗

PubMed2005

Strategies for producing faster acting antidepressants.

Existing antidepressant treatments exhibit limited efficacy and a slow onset of action. Several neurobiological adaptive mechanisms might delay the clinical effects of antidepressants, whose therapeutic action is primarily triggered by an increase of serotonergic and noradrenergic neurotransmission. Here, we review several potential mechanisms that could be useful to increase the speed of current antidepressant drugs, such as additional blockade of aminergic autoreceptors or antagonism of certain postsynaptic (5-HT2A, 5-HT2C) receptors. The potential use of strategies not based on monoaminergic transmission, such as CRF and NK1 receptor antagonists, or more novel strategies, based on glutamatergic or GABAergic transmission or on intracellular messengers, are also reviewed.

Animals↗

PubMed2005

Cell proliferation is reduced in the dentate gyrus of aged but not young Ts65Dn mice, a model of Down syndrome.

Reduced number of neurons is a common feature in Down's syndrome (DS) brains. Since reduced neuronal number also occurs in the dentate gyrus of Ts65Dn mice (TS), a model for DS, hippocampal cell proliferation and survival were analyzed in young and old TS mice. For evaluating proliferation and survival, half of the mice were sacrificed 1 day, and the other half 30 days after the last bromodeoxyuridine injection, respectively. No difference was found in the number of proliferating or surviving cells of young TS and control mice. An age-associated decline in total cell number and density has been found in both genotypes, this decline being more pronounced in TS animals. Thus, aged TS mice showed reduced cell proliferation and density of surviving cells compared to CO mice. Due to the putative involvement of newborn cells in the dentate gyrus in learning processes, the reduced proliferative capacity found in TS mice could be involved in the cognitive problems found in this model of Down syndrome.

Age Factors↗

PubMed2005

Autoradiographic characterisation of [35S]GTPgammaS binding stimulation mediated by 5-HT1B receptor in postmortem human brain.

G-protein activation mediated by 5-HT1B receptors was studied in human brain by [35S]GTPgammaS autoradiographic methods. 5-HT (10 microM) increased [35S]GTPgammaS binding in caudate-putamen nucleus, globus pallidus, dentate gyrus, CA1, entorhinal cortex and substantia nigra. In basal ganglia and midbrain, this effect was blocked by GR 127935 (5-HT(1B/1D) antagonist). In contrast, WAY 100635 (selective 5-HT1A antagonist) reversed the effect of 5-HT in hippocampus and entorhinal cortex. Therefore, a detailed pharmacological study was carried out in basal ganglia and substantia nigra using 5-HT and the 5-HT(1B/1D) agonists GTI and CP 93129. In these areas, these agonists stimulated [35S]GTPgammaS binding in a concentration-dependent manner, with no significant differences in the potency for a given structure. Furthermore, GTI was more potent in the putamen than in globus pallidus. In caudate-putamen, the three agonists showed the same efficacy, while in globus pallidus and substantia nigra the efficacy of 5-HT was higher than GTI and CP 93129. The selective 5-HT1B antagonist SB-224289 inhibited GTI- and CP 93129-stimulated [35S]GTPgammaS binding in basal ganglia and substantia nigra, while coincubation with BRL 15572 (selective 5-HT1D antagonist) did not result in any significant change. Here we report the anatomical pattern of distribution of 5-HT1B-dependent functionality by using specific pharmacological tools in human brain sections.

Aged↗

PubMed2004

A single in-vivo exposure to delta 9THC blocks endocannabinoid-mediated synaptic plasticity.

Endogenous cannabinoids (eCB) mediate synaptic plasticity in brain regions involved in learning and reward. Here we show that in mice, a single in-vivo exposure to Delta 9-tetrahydrocannabinol (THC) abolishes the retrograde signaling that underlies eCB-mediated synaptic plasticity in both nucleus accumbens (NAc) and hippocampus in vitro. This effect is reversible within 3 days and is associated with a transient modification in the functional properties of cannabinoid receptors.

Animals↗

PubMed2003

Adenylate cyclase activity in postmortem brain of suicide subjects: reduced response to beta-adrenergic stimulation.

BACKGROUND: Biochemical research on the etiopathogenesis of affective disorders has focused on transduction mechanisms beyond receptors, such as adenylate cyclase activity. METHODS: Adenylate cyclase activity (AC) was measured in postmortem frontal cortex samples from 11 suicide victims with a firm antemortem diagnosis of major depressive disorder and 11 matched control cases. We analyzed the basal activity of the enzyme and that following stimulation with forskolin, guanine nucleotides, and the beta(1)-adrenoceptor agonist xamoterol. RESULTS: A significant negative correlation between the period of tissue storage and the response of AC to the different stimuli assayed was observed. No difference was found in the levels of basal, forskolin-, and GTPgammaS-stimulated activity between control and major depressive disorder cases, both in the drug-free and the drug-treated subgroups. In contrast, we found a significant lower response to beta(1)-adrenoceptors agonist-stimulated AC activity in the major depressive disorder group (p <.01). This pattern of reduced response was also found in the subgroup of patients with negative toxicology for antidepressants. CONCLUSIONS: These results, directly obtained from the brain of depressed patients, reinforce the involvement of noradrenergic neurotransmission in depressive illness. They also support the relevance of cyclic adenosine monophosphate signaling pathways in the etiopathogenesis of affective disorders.

Adenylyl Cyclases↗

PubMed2003

Autoradiographic distribution of 5-HT7 receptors in the human brain using [3H]mesulergine: comparison to other mammalian species.

1. The main aim of this investigation was to delineate the distribution of the 5-HT(7) receptor in human brain. Autoradiographic studies in guinea-pig and rat brain were also carried out in order to revisit and compare the anatomical distribution of 5-HT(7) receptors in different mammalian species. 2. Binding studies were performed in rat frontal cortex membranes using 10 nm [(3)H]mesulergine in the presence of raclopride (10 microm) and DOI (0.8 microm). Under these conditions, a binding site with pharmacological characteristics consistent with those of the 5-HT(7) receptors was identified (rank order of binding affinity values: 5-CT>5-HT>5-MeOT>mesulergine approximately methiothepin>8-OH-DPAT=spiperone approximately (+)-butaclamol>>imipramine approximately (+/-)-pindolol>>ondansetron approximately clonidine approximately prazosin). 3. The autoradiographic studies revealed that the anatomical distribution of 5-HT(7) receptors throughout the human brain was heterogenous. High densities were found over the caudate and putamen nuclei, the pyramidal layer of the CA2 field of the hippocampus, the centromedial thalamic nucleus, and the dorsal raphe nucleus. The inner layer of the frontal cortex, the dentate gyrus of the hippocampus, the subthalamic nucleus and superior colliculus, among others, presented intermediate concentrations of 5-HT(7) receptors. A similar brain anatomical distribution of 5-HT(7) receptors was observed in all three mammalian species studied. 4. By using [(3)H]mesulergine, we have mapped for the first time the anatomical distribution of 5-HT(7) receptors in the human brain, overcoming the limitations previously found in radiometric studies with other radioligands, and also revisiting the distribution in guinea-pig and rat brain.

5-Methoxytryptamine↗

PubMed2003

Chronic fluoxetine induces opposite changes in G protein coupling at pre and postsynaptic 5-HT1A receptors in rat brain.

Chronic treatment with the antidepressant fluoxetine may lead to changes in the properties of pre- and postsynaptic 5-HT(1A) receptors due to modifications in the receptor-G protein coupling process. We have evaluated, in rats, the effect of chronic fluoxetine (10 mg/kg/day) at brain 5-HT(1A) receptors using different techniques. The density of 5-HT(1A) receptors was unchanged in fluoxetine-treated rats vs. vehicle group. Stimulation of [(35)S]GTPgammaS binding induced by (+/-)8-OH-DPAT was significantly attenuated in dorsal raphe nucleus after fluoxetine (+3.7 vs. +31.2% in vehicle). The inhibition of dorsal raphe firing by (+/-)8-OH-DPAT (ED(50) in vehicle = 2.1 microg/kg, i.v.) was also attenuated in rats treated with fluoxetine (ED(50)=4.7 microg/kg). In contrast, a significant increase on (+/-)8-OH-DPAT-induced stimulation of [(35)S]GTPgammaS binding was observed in CA(1) (+53.4 vs.+20.2% in vehicle) and dentate gyrus (+105.7 vs. +52.6% in vehicle) but not in entorhinal cortex. Our data demonstrate that fluoxetine-induced desensitization of 5-HT(1A) autoreceptors occurs at G protein level. Moreover, a relevant finding is the region-specific hypersensitivity of postsynaptic 5-HT(1A) receptors, in the hippocampus but not in entorhinal cortex, following chronic fluoxetine. These differential adaptive changes in brain 5-HT(1A) receptors could underlie the mechanism of action of antidepressants and also contribute to their clinical effects.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2003

Ontogenetic development of cannabinoid receptor expression and signal transduction functionality in the human brain.

Previous evidence suggests that the endogenous cannabinoid system emerges relatively early during brain development in the rat. However, the pre- and postnatal pattern of appearance of CB1 cannabinoid receptors in humans has not been analysed in detail. Furthermore, there is a complete lack of information about the functional ability of these proteins to activate signal transduction mechanisms during human development. In the present study we have explored CB1 receptor expression throughout the different areas of the developing human brain by [3H]CP55 940 autoradiography. We have also assessed CB1 functional coupling to G proteins during brain development by agonist-stimulated [35S]GTPgammaS autoradiography in the same cases. Our results indicate a significant density of cannabinoid receptors at 19 weeks' gestation in the same areas that contain these receptors in the adult human brain. Autoradiographic levels of CB1 receptors in these structures seem to increase progressively from early prenatal stages to adulthood. Interestingly, high densities of cannabinoid receptors have also been detected during prenatal development in fibre-enriched areas that are practically devoid of them in the adult brain. In parallel with these data, we have found that brain cannabinoid receptors are functionally coupled to signal transduction mechanisms from early prenatal stages. This early pattern of expression of functionally active cannabinoid receptors, along with the transient and atypical localization of these proteins in white matter areas during the prenatal stages, suggest an specific role of the endocannabinoid system in the events related to human neural development.

Brain↗

PubMed2002

Flip and flop splice variants of AMPA receptor subunits in the spinal cord of amyotrophic lateral sclerosis.

Excitotoxicity mediated by AMPA receptors has been suggested to be implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). To investigate the relevance of AMPA receptors to motor neuron degeneration in ALS, we evaluated the expression of mRNAs coding for flip and flop splice variants of AMPA receptor subunits (GluR-A to GluR-D) in the cervical segment of the spinal cord from control individuals and patients with ALS using in situ hybridization histochemistry. Transcript mRNAs coding for flop variants were significantly decreased in the ventral horn of the spinal cord from patients with ALS, whereas the mRNAs for flip variants were preserved. These findings suggest that the relative abundance of flip variants vs. flop variants is increased in spinal motor neurons of ALS patients when compared to that of control individuals. Flip variants promote assemblies of slowly desensitizing AMPA receptors. These results imply that spinal motor neurons of ALS patients possess more slowly desensitizing AMPA receptors than those of control individuals. This expression change of AMPA receptors in ALS may account for vulnerability of motor neurons in this disease.

Adult↗

PubMed2002

Cannabinoid receptor antagonism and inverse agonism in response to SR141716A on cAMP production in human and rat brain.

The effects of cannabinoid drugs on cAMP production were examined in mammalian brain. The cannabinoid receptor agonist (R)-(+)-[2,3-dihydro-5-methyl-3-[(4-morpholinyl)methyl]pyrrolo[1,2,3,-d,e-1,4-benzoxazin-6-yl]-(1-naphthalenyl) methanone (WIN55,212-2) decreased forskolin-induced cAMP accumulation in a concentration-dependent manner (10(-8)-10(-5) M) in membranes from several rat and human brain regions, this effect being antagonized by 10(-5) M N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A). Furthermore, high micromolar concentrations of SR141716A evoked a dose-dependent increase in basal cAMP in rat cerebellum and cortex, as well as in human frontal cortex. This effect was antagonized by WIN55,212-2 and abolished by N-ethylmaleimide, consistent with the involvement of cannabinoid CB(1) receptors through the activation of G(i/o) proteins. These results suggest a ligand-independent activity for cannabinoid CB(1) receptor signaling cascade in mammalian brain.

Animals↗

PubMed2000

Opioid tolerance and supersensitivity induce regional changes in the autoradiographic density of dihydropyridine-sensitive calcium channels in the rat central nervous system.

Chronic opioid administration induces adaptations in neurones resulting in opioid tolerance and dependence. The changes in dihydropyridine (DHP)-sensitive Ca(2+) channels (L-type) associated with tolerance and supersensitivity to the antinociceptive effect of the micro-opioid receptor agonist sufentanil were analyzed in the central nervous system (CNS) of rats. Autoradiographic assays were performed with [(3)H]PN-200-110 (isopropyl 4-(2,1, 3-benzoxadiazol-4-yl)-1,4-dihydro-2, 6-dimethyl-5-methoxycarbonylpyridine-3-carboxylate). Chronic s.c. infusion of sufentanil (2 microg/h) for 7 days, which has been shown to induce tolerance to the opioid antinociceptive effect, produced an up-regulation of DHP binding sites. The highest increases in density were localized in regions involved in nociceptive transmission and perception, such as the dorsal horn of the spinal cord, the dorsal raphe nucleus, the central grey matter, the thalamic nuclei, and the somatosensory cortex. Animals were rendered supersensitive to the antinociceptive effect of sufentanil by chronic and simultaneous infusion of sufentanil (2 microg/h) and nimodipine (1 microg/h) for 7 days. Under these conditions, a greater increase in the number of DHP binding sites was observed in the spinal cord, central grey matter, dorsal raphe nucleus, and somatosensory neocortex, when compared to the sufentanil group. The role of an increased influx through L-type channels in opioid tolerance is reinforced, whereas their persistent blockade is essential for the expression of opioid supersensitivity.

Animals↗