Neuroscience
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We recently reported that exogenously applied orphanin FQ, the endogenous ligand for opioid receptor-like 1 (ORL(1)) receptor, produces sex-specific modulation of trigeminal nociception, and that estrogen contributes to these sex-related differences. Estrogen could produce these sex-related differences by altering the expression of the ORL(1)-receptor gene in the trigeminal nucleus caudalis. Utilizing in situ hybridization, we compared levels of ORL(1) receptor mRNA and investigated its colocalization with estrogen receptor mRNA in trigeminal neurons. ⋯ Levels were reduced to proestrus levels in these regions following estradiol replacement. Our results also showed that ORL(1) receptor mRNA is present in majority of estrogen receptor (alpha and/or beta) mRNA-containing neurons. We conclude that there are sex-related differences in the ORL(1)-receptor gene expression in the trigeminal nucleus caudalis, which appear to be determined in part by estrogen levels.
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Comparative Study
Retinotopic map plasticity in adult cat visual cortex is accompanied by changes in Ca2+/calmodulin-dependent protein kinase II alpha autophosphorylation.
In adult cats, the induction of homonymous binocular central retinal lesions causes a dramatic reorganization of the topographic map in the sensory-deprived region of the primary visual cortex. To investigate the possible involvement of the alpha-subunit of the calcium/calmodulin dependent protein kinase type II (alphaCaMKII) in this form of brain plasticity, we performed in situ hybridization and Western blotting experiments to analyze mRNA, protein and autophosphorylation levels of this multifunctional kinase. No differences in the mRNA or protein levels were observed between the central, sensory-deprived and the peripheral, non-deprived regions of area 17 of retinal lesion animals or between corresponding cortical regions of normal control animals. ⋯ In contrast, a post-lesion survival time of 14 days resulted in a alphaCaMKII autophosphorylation level that was four times higher in visually-deprived area 17 than in the non-deprived cortical region. This increased phosphorylation state is not a direct consequence of the decrease in visual activity in these neurons, because we would have expected to see a similar change at shorter or longer post-lesion survival times or in the visually deprived visual cortex of animals in which the left optic tract and the corpus callosum were surgically cut. No such changes were observed, leading to the conclusion that the phosphorylation changes observed at 14 days are related to a delayed reorganization of the retinotopic map of the striate cortex.
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In the present study, the expression of the HuC/D RNA-binding proteins, a marker of neurons that have left the mitotic cycle, in cells migrating from the olfactory neuroepithelium toward the telencephalon in the chick embryo was investigated by means of immunofluorescence and confocal laser microscopy. Results showed that this migratory cell population is early and massively labeled by the a-HuC/D antibody starting from the first olfactory pit stage. At this developmental stage, olfactory migratory cells appeared to be the only neuronal population that expressed the HuC/D antigens in the whole embryo. ⋯ HuC/D immunopositivity persisted until stage 30 HH (about 6.5 days), the later developmental stage investigated in this study, when colocalization with GnRH was detected. Negativity to the anti-proliferating cell nuclear antigen (anti-PCNA) immunostaining, a marker of S-phase, showed that migratory olfactory cells have left the mitotic cycle. Altogether, these results suggest that we have identified the first population of post-mitotic neurons in the developing nervous system of the chick embryo.
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Comparative Study
Basolateral amygdala lesions impair both cue- and cocaine-induced reinstatement in animals trained on a discriminative stimulus task.
Drug-associated environmental cues can maintain drug use and contribute to relapse even after long periods of abstinence. We investigated the ability of sensory stimuli that signaled periods of reward availability to sustain cocaine self-administration and trigger the reinstatement of reward-seeking behavior. We demonstrate that lesions of the basolateral amygdala (BLA), a structure strongly implicated in attributing salience to environmental stimuli, significantly reduced the power of predictive cues to elicit reward-seeking behavior. ⋯ In sham-lesioned animals, cocaine and the DS, but not the CS or the S-, triggered reinstatement. BLA lesions abolished DS-induced reinstatement and significantly attenuated cocaine-induced reinstatement. These results demonstrate 1) that when tested under the same conditions, a discriminative cue which signals reward availability is a more robust trigger of reward-seeking than a Pavlovian CS which signals reward delivery and 2) that the BLA contributes to reinstatement in response to these discriminative cues.
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Comparative Study
Long-term effects of maternal separation on ethanol intake and brain opioid and dopamine receptors in male Wistar rats.
Accumulating evidence indicates that an animal's response to a drug can be profoundly affected by early environmental influences. The brain opioid and dopamine systems may play a critical role in these effects, since various types of stress and drugs of abuse promote alterations in these brain systems. To study this further, we investigated long-term behavioural and neurochemical effects of repeated maternal separation in male Wistar rats. ⋯ Ethanol-induced changes were observed in D(2)-like receptor density in the ventral tegmental area in MS360, and in the ventral tegmental area and frontal-parietal cortex in animal facility-reared rats. These findings show that early experiences can induce long-lasting changes in especially brain dopamine receptor density and that ethanol consumption induces alterations in opioid and dopamine receptor density in distinct brain areas. It is also suggested that changes induced by repeated MS15 may provide protection against high voluntary ethanol intake.