RESUMO
BACKGROUND: Basolateral amygdala (BLA) excitatory projections to medial prefrontal cortex (PFC) play a key role controlling stress behavior, pain, and fear. Indeed, stressful events block synaptic plasticity at the BLA-PFC circuit. The stress responses involve the action of corticotrophin releasing factor (CRF) through type 1 and type 2 CRF receptors (CRF1 and CRF2). Interestingly, it has been described that dopamine receptor 1 (D1R) and CRF peptide have a modulatory role of BLA-PFC transmission. However, the participation of CRF1 and CRF2 receptors in BLA-PFC synaptic transmission still is unclear. METHODS: We used in vivo microdialysis to determine dopamine and glutamate (GLU) extracellular levels in PFC after BLA stimulation. Immunofluorescence anatomical studies in rat PFC synaptosomes devoid of postsynaptic elements were performed to determine the presence of D1R and CRF2 receptors in synaptical nerve endings. RESULTS: Here, we provide direct evidence of the opposite role that CRF receptors exert over dopamine extracellular levels in the PFC. We also show that D1R colocalizes with CRF2 receptors in PFC nerve terminals. Intra-PFC infusion of antisauvagine-30, a CRF2 receptor antagonist, increased PFC GLU extracellular levels induced by BLA activation. Interestingly, the increase in GLU release observed in the presence of antisauvagine-30 was significantly reduced by incubation with SCH23390, a D1R antagonist. CONCLUSION: PFC CRF2 receptor unmasks D1R effect over glutamatergic transmission of the BLA-PFC circuit. Overall, CRF2 receptor emerges as a new modulator of BLA to PFC glutamatergic transmission, thus playing a potential role in emotional disorders.
Assuntos
Complexo Nuclear Basolateral da Amígdala/metabolismo , Dopamina/metabolismo , Ácido Glutâmico/metabolismo , Córtex Pré-Frontal/metabolismo , Receptores de Hormônio Liberador da Corticotropina/metabolismo , Receptores de Dopamina D1/metabolismo , Animais , Masculino , Microdiálise , Ratos , Ratos Sprague-DawleyRESUMO
Steroid sex hormones produce physiological effects in reproductive tissues and also in nonreproductive tissues, such as the brain, particularly in cortical, limbic and midbrain areas. Dopamine (DA) neurones involved in processes such as prolactin secretion (tuberoinfundibular system), motor circuit regulation (nigrostriatal system) and driving of motivated behaviour (mesocorticolimbic system) are specially regulated by sex hormones. Indeed, sex hormones promote neurochemical and behavioural effects induced by drugs of abuse by tuning midbrain DA neurones in adult animals. However, the long-term effects induced by neonatal exposure to sex hormones on dopaminergic neurotransmission have not been fully studied. The present study aimed to determine whether a single neonatal exposure with oestradiol valerate (EV) results in a programming of dopaminergic neurotransmission in the nucleus accumbens (NAcc) of adult female rats. To answer this question, electrophysiological, neurochemical, cellular, molecular and behavioural techniques were used. The data show that frequency but not amplitude of the spontaneous excitatory postsynaptic current is significantly increased in NAcc medium spiny neurones of EV-treated rats. In addition, DA content and release are both increased in the NAcc of EV-treated rats, caused by an increased synthesis of this neurotransmitter. These results are functionally associated with a higher percentage of EV-treated rats conditioned to morphine, a drug of abuse, compared to controls. In conclusion, neonatal programming with oestradiol increases NAcc dopaminergic neurotransmission in adulthood, which may be associated with increased reinforcing effects of drugs of abuse.
Assuntos
Condicionamento Operante/efeitos dos fármacos , Dopamina/metabolismo , Estradiol/farmacologia , Morfina/farmacologia , Neurônios/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Analgésicos Opioides/farmacologia , Animais , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/metabolismo , Estrogênios/farmacologia , Feminino , Neurônios/metabolismo , Núcleo Accumbens/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
The aim was to determine if vitamins E and C inhibit the release of cortisol from bovine adrenocortical cells when stimulated with ACTH in vitro. A factorial arrangement of treatments was used to culture bovine adrenocortical cells with different concentrations of vitamins E and C [(+)-α-tocopherol at 0, 2.3, and 16 µM and l-ascorbic acid at 0, 15, and 50 µM]. After 3 and 7 d of vitamin treatments, cell cultures were stimulated with ACTH (1 nM) for 24h and the culture medium extracted to measure cortisol released by the cells using HPLC with UV detection. Vitamin E, vitamin C, or their combination did not affect the amount of cortisol released by the adrenal cultures to the media. Cortisol released by the adrenal cultures ranged from 33.6±6.85 to 49.7±8.01 nmol per 10(7) cells. The modulation effect of vitamins E and C on the stress response does not take place at the cortex of the adrenal gland.
Assuntos
Córtex Suprarrenal/efeitos dos fármacos , Ácido Ascórbico/farmacologia , Hidrocortisona/biossíntese , Vitamina E/farmacologia , Vitaminas/farmacologia , Córtex Suprarrenal/citologia , Córtex Suprarrenal/metabolismo , Hormônio Adrenocorticotrópico/metabolismo , Animais , Bovinos , Células Cultivadas , Técnicas In VitroRESUMO
The expression of mesencephalic brain derived neurotrophic factor (BDNF) has been shown to be regulated by dopaminergic neuronal functioning and glutamate receptors (GluRs). In turn, BDNF participates in the regulation of mesencephalic GluRs' expression. In the present study we analyzed, using semi-quantitative RT-PCR, the effect of BDNF as well as of the GluRs agonists NMDA and trans-(+/-)-1-Amino-(1S,3R)-cyclopentane dicarboxylic acid (t-ACPD), on the expression levels of the NMDA GluR subunit 1 (NR1) mRNA, using rat cultured mesencephalic neurons. In the course of this study, a novel rat mRNA splice variant of NR1 was identified. This new NR1 mRNA isoform is characterized by the insertion of an 82 base pair intron containing an inframe stop codon, thus predicting the expression of a putative truncated protein of 465 amino acids. The RT-PCR and in situ hybridization reveals that the novel NR1 mRNA is expressed in various brain regions of the rat embryo, whereas no expression was detected in the adult rat brain. The modulation of the novel NR1 mRNA isoform by both BDNF and the metabotropic GluR agonist t-ACPD, suggests that the resulting putative NR1 truncated protein may be relevant in the regulatory network of glutamatergic neurotransmission in the developing central nervous system.
Assuntos
Processamento Alternativo/genética , Química Encefálica/genética , Encéfalo/embriologia , Receptores de N-Metil-D-Aspartato/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Fator Neurotrófico Derivado do Encéfalo/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Clonagem Molecular , Cicloleucina/análogos & derivados , Cicloleucina/farmacologia , Feminino , Hibridização In Situ , Mesencéfalo/citologia , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/metabolismo , Dados de Sequência Molecular , Gravidez , RNA Mensageiro/biossíntese , RNA Mensageiro/isolamento & purificação , Ratos , Receptor trkB/agonistas , Receptores de N-Metil-D-Aspartato/agonistas , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The bed nucleus of the stria terminalis pars ventralis (vBNST) receives dense noradrenergic terminals and contains the highest concentration of noradrenaline (NA) in the brain. We used autoradiography following retrograde axonal transport of [(3)H]-NA to identify selectively whether noradrenergic neurons innervating the vBNST originate in the medulla oblongata and/or the locus coeruleus. In combination with this technique, non-isotopic in situ hybridization for the NMDA-NR1 receptor subunit mRNA was used to examine, on the same brain sections, its expression in noradrenergic neurons that innervate the vBNST. The results showed that 60 +/- 6% and 35 +/- 7% of the total number of radiolabeled cells detected after injection of [(3)H]-NA in the vBNST were located in brainstems A1 and A2 noradrenergic cell groups, respectively. In addition, 18.5 +/- 4.2% of radiolabeled cells in A1 and 15.7 +/- 5% in A2 also expressed the mRNA for the NMDA-NR1 receptor subunit. In contrast, only 4 +/- 3% of the radiolabeled cells were present in the locus coeruleus, and none of these cells was positive to NMDA-NR1 receptor subunit mRNA. The present results provide evidence that BNST noradrenergic fibers and terminals originate predominantly from A1 and A2 noradrenergic cell groups, and that a significant number of these noradrenergic neurons also express the mRNA for the NMDA-NR1 receptor subunit. The observation that brainstem noradrenergic neurons innervating the vBNST express NMDA receptor mRNA gives anatomical support to the regulation of NA release by NMDA presynaptic receptors.
Assuntos
Neurônios/metabolismo , Norepinefrina/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Núcleos Septais/citologia , Simpatomiméticos/metabolismo , Animais , Autorradiografia , Expressão Gênica/fisiologia , Hibridização In Situ , Masculino , Neurônios/química , Norepinefrina/farmacologia , RNA Mensageiro/análise , Ensaio Radioligante , Núcleos da Rafe/química , Núcleos da Rafe/citologia , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/análise , Núcleos Septais/química , Simpatomiméticos/farmacologia , TrítioRESUMO
The participation of N-methyl-d-aspartate (NMDA) receptors on dopamine (DA) efflux in the striatum of anaesthetized rats, which had their DA nigrostriatal pathway previously lesioned with different doses of 6-hydroxydopamine (6-OH-DA), was assessed by in vivo microdialysis methodology. In addition, the in vivo basal DA and dihydroxy-phenyl-acetic acid (DOPAC) effluxes and the effect of local K+-depolarization on DA release were also evaluated in the striatum of these 6-OH-DA treated rats. Lesioned rats were divided in three groups corresponding to animals with 25-75%, 75-95% and >95% of striatum tissue DA depletion, respectively. Striatal DA tissue depletion between 25-75% occurred in parallel with a 30% reduction in DA extracellular levels, with a moderate 10% increase in basal fractional DA efflux, and with no statistical changes in the fractional DA efflux induced by NMDA (500 microM) receptor stimulation by reverse dialysis. Rats with higher DA tissue depletion (between 75-95%) exhibited a 60% reduction in DA extracellular levels in the striatum and this reduction occurred in parallel with a modest rise in basal fractional DA efflux, but with a striking decrease in the NMDA-induced fractional DA efflux. In rats with extreme or >95% of striatal DA tissue depletion, basal fractional DA efflux in the striatum increased quite substantially along with a recovery in the ability of NMDA receptor stimulation to induce fractional DA release. The >95% striatal DA-depleted rats also exhibited a significant decrease in tissue and extracellular DOPAC/DA ratio when compared to sham and partially DA-depleted rats. In contrast to the previous results, fractional DA efflux induced by reverse dialysis with K+ (40 mM) remained the same in the striatum of sham and all groups of DA-tissue depleted rats. The present findings suggest the existence of at least three features associated to the regulation of basal and NMDA-induced extracellular levels of DA in the striatum of rats as a function of striatal tissue DA depletion produced by 6-OH-DA. They also support the view that a differential regulation of basal and NMDA-induced DA extracellular levels occur in partial and extreme DA-depleted striatum after 6-OH-DA treatment. Such findings may have implications as regard to the participation of the NMDA receptor in the compensatory mechanisms associated to the progress of Parkinson's disease, as well as in the therapeutic treatment of this neurological disorder.
Assuntos
Corpo Estriado/citologia , Corpo Estriado/metabolismo , Dopamina/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Substância Negra/citologia , Ácido 3,4-Di-Hidroxifenilacético/metabolismo , Animais , Química Encefálica/efeitos dos fármacos , Corpo Estriado/química , Denervação , Maleato de Dizocilpina/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Espaço Extracelular/química , Espaço Extracelular/metabolismo , Masculino , Microdiálise , Vias Neurais , Oxidopamina , Potássio/farmacologia , Ratos , Ratos Sprague-Dawley , SimpatolíticosRESUMO
Antisense digoxigenin-labeled deoxyoligonucleotides probes and non-isotopic in situ hybridization (HIS) techniques have been used to explore the NMDA-NR1 receptor subunit mRNA distribution in different brain areas of rats which had their dopaminergic nigrostriatal pathway previously lesioned with intracerebral administration of 6-OH-dopamine (6-OH-DA). Intense and significant hybridization signals for NR1 mRNA were found in dentate gyrus and regions CA1-CA2-CA3 of the hippocampus, in layers II-III and V-VI of the cerebral cortex, and in the cerebellum of sham-treated rats. Basal ganglia structures such as the striatum exhibited few NR1 mRNA hybridization signals as compared to the hippocampus and cerebral cortex. In contrast, both zona compacta and reticulata of substantia nigra (SN) showed a reduced number of cells with nevertheless intense NR1 mRNA HIS signals. The NR1 mRNA distribution in the brain was affected in a brain regional selective manner by 6-OH-DA induced lesions of DA neuronal systems. A striking increase in NR1 mRNA HIS signals was observed in both striata after unilateral lesioning with 6-OH-DA. Instead, in SN compacta but not in reticulata, a moderate but significant bilateral reduction of NR1 mRNA was observed after unilateral 6-OH-DA injection. No significant changes in NR1 mRNA were detected in cerebral cortex and other brain regions after 6-OH-DA treatment. These studies, and others reported in the literature, support the view that extensive lesions of nigrostriatal DA-containing neurons in the brain may trigger compensatory or adaptative responses in basal ganglia structures such as striatum and substantia nigra which involve glutamateric neurons and the genic expression of NMDA receptors.
Assuntos
Encéfalo/efeitos dos fármacos , Fragmentos de Peptídeos/genética , RNA Mensageiro/biossíntese , Receptores de N-Metil-D-Aspartato/química , Animais , Encéfalo/metabolismo , Hibridização In Situ/métodos , Técnicas In Vitro , Masculino , Neurotoxinas , Oxidopamina , Ratos , Ratos Sprague-DawleyRESUMO
After 5 weeks of haloperidol, positive symptoms in drug-naive schizophrenic patients substantially subsided. Negative symptoms, although with a different temporal pattern, decreased after the fifth week of haloperidol treatment; specifically, a decrease was seen in anhedonia and affective flattening, whereas avolition-apathy and attentional impairment presented no changes. Alogia showed a decrease during the third week and a trend to return to placebo scores during weeks 4 and 5. Changes in affective flattening, alogia and attentional impairment correlated with changes in positive symptoms. During placebo, plasma homovanillic acid (HVA) correlated with negative symptoms and with changes presented by negative symptoms between the first and the fifth treatment week. These data show that negative symptoms respond differentially to neuroleptics and suggest that avolition-apathy may represent a different behavioral component of the schizophrenia process.