Neuroscience
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We have previously demonstrated that male rats exposed to stress during the last week of gestation present age-specific impairments of brain development. Since the organization of the fetal developing brain is subject to androgen exposure and prenatal stress was reported to disrupt perinatal testosterone surges, the aim of this research was to explore whether abnormal androgen concentrations during late gestation affects the morphology of the prefrontal cortex (PFC), hippocampus (HPC) and ventral tegmental area (VTA), three major areas that were shown to be affected by prenatal stress in our previous studies. We administered 10-mg/kg/day of the androgen receptor antagonist flutamide (4'nitro-3'-trifluoromethylsobutyranilide) or vehicle injections to pregnant rats from days 15-21 of gestation. ⋯ Brain morphological studies revealed that prenatal flutamide decreased the number of MAP2 (a microtubule-associated protein type 2, present almost exclusively in dendrites) immunoreactive neuronal processes in all evaluated brain areas, both in prepubertal and adult offspring, suggesting that prenatal androgen disruption induces long-term reductions of the dendritic arborization of several brain structures, affecting the normal connectivity between areas. Moreover, the number of tyrosine hydroxylase (TH)-immunopositive neurons in the VTA of prepubertal offspring was reduced in flutamide rats but reach normal values at adulthood. Our results demonstrate that the effects of prenatal flutamide on the offspring brain morphology resemble several prenatal stress effects suggesting that the mechanism of action of prenatal stress might be related to the impairment of the organizational role of androgens on brain development.
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Memories of drug experience and drug-associated environmental cues can elicit drug-seeking and taking behaviors in humans. Disruption of reconsolidation of drug memories dampens previous memories and therefore may provide a useful way to treat drug abuse. We and others previously demonstrated that dopamine D1 and D3 receptors play differential roles in acquiring cocaine-induced behaviors. ⋯ In contrast, with no memory retrieval, pharmacological antagonism of D1 receptors or the D3 receptor gene mutation did not significantly affect reconsolidation of cocaine memories. Pharmacological blockade of D3 receptors also attenuated reconsolidation in wild-type mice that lasted for at least 1week after the memory retrieval. These results suggest that D1 and D3 receptors and related signaling mechanisms play key roles in reconsolidation of cocaine memories in mice, and that these receptors may serve as novel targets for the treatment of cocaine abuse in humans.
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Alzheimer's disease (AD) is the most common and devastating neurodegenerative disease. The etiology of AD has yet to be fully understood, and common treatments remain largely non-efficacious. The amyloid hypothesis posits that extracellular amyloid-β (Aβ) deposits are the fundamental etiological factor of the disease. ⋯ Chronic exposure to (PhSe)2 attenuated oxidative stress induced by Aβ1-42, with concomitant recovery of associative learning memory in C. elegans. Additionally, (PhSe)2 decreased Aβ1-42 transgene expression, suppressed Aβ1-42 peptide, and downregulated hsp-16.2 by reducing the need for this chaperone under Aβ1-42-induced toxicity. These observations suggest that (PhSe)2 plays an important role in protecting against oxidative stress-induced toxicity, thus representing a promising pharmaceutical modality that attenuates Aβ1-42 expression.
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Depending on an animal's behavioral state, hippocampal CA1 pyramidal cells receive distinct patterns of excitatory and inhibitory synaptic inputs. The time-dependent changes in the frequencies of these inputs and the nonuniform distribution of voltage-gated channels lead to dynamic fluctuations in membrane conductance. In this study, using a whole-cell patch-clamp method, we attempted to record and analyze the frequency dependencies of membrane responsiveness in Wistar rat hippocampal CA1 pyramidal cells following noise current injection directly into dendrites and somata under pharmacological blockade of all synaptic inputs. ⋯ The low-pass filtering properties in the apical dendrites were more enhanced by membrane depolarization than those in the somata. Coherence spectral analysis revealed high coherence between the input signal and the output voltage response in the theta-gamma frequency range, and large lags emerged in the distal dendrites in the gamma frequency range. Our results suggest that apical dendrites of hippocampal CA1 pyramidal cells integrate synaptic inputs according to the frequency components of the input signal along the dendritic segments receiving the inputs.
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5-Hydroxytrytamine (serotonin) type 3A receptors (5-HT3ARs), as the only ligand-gated ion channels in the serotonin receptor family, are known to regulate neuronal excitation and release of GABA in hippocampal interneurons. However, their physiological role in glutamatergic synaptic plasticity remains unclear. Here, we show that deletion of the 5-HT3AR gene in transgenic mice abolished N-methyl-d-aspartate (NMDA) receptor (NMDAR)-dependent long-term depression (LTD) induced by low-frequency stimulation (LFS) in hippocampal CA1 synapses in slices, whereas the metabotropic glutamate receptor (mGluR)-dependent LTD did not change in the 5-HT3AR knockout mice. ⋯ However, the deletion of 5-HT3ARs did not lead to loss of synapses and structural alteration of dendritic spines. Furthermore, the concentrations of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in the hippocampus were not affected by the deletion of 5-HT3ARs. These observations revealed an important role of 5-HT3ARs in NMDAR-dependent long-term depression, which is critical for learning behaviors.