Neuroscience
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Previous studies showed that early environmental conditions severely affect the morphology of the granule cells in the hippocampal dentate gyrus and pyramidal neurons in fields CA3 and CA1. The aim of the present study was to determine whether early isolation affects neuron morphology in layer II of the entorhinal cortex, from which the perforant path to the dentate gyrus and CA3 takes its origin. Male and female guinea pigs were assigned at 6-7 days of age to either a control (social) or an isolated environment where they remained for 80-90 days. ⋯ The results indicate that early isolation affects the structure of the star cells in the entorhinal cortex and that males and females react to isolation in an opposite manner. A similar sexually dimorphic response to early isolation was previously observed in the dentate gyrus and fields CA3 and CA1. The presence of widespread effects of isolation in the entorhinal cortex and numerous hippocampal structures suggests that the outcome of early isolation might be a change in learning and memory functions requiring the hippocampal region.
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Sleep is an unavoidable activity of the brain. The delay of the time to sleep (sleep deprivation), induces an increase of slow-wave sleep and rapid-eye-movement (REM) sleep (rebound) once the subject is allowed to sleep. This drive to sleep has been hypothesized to be dependent on the accumulation of sleep-inducing molecules and on the high expression of these molecule receptors. ⋯ Results indicated that SR141716A prevents REM sleep rebound and REM sleep deprivation does not modify the expression of the CB1 protein or mRNA. However, REM sleep deprivation plus 2 h of sleep rebound increased the CB1 receptor protein and, slightly but significantly, decreased mRNA expression. These results suggest that endocannabinoids may be participating in the expression of REM sleep rebound.
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The specific role of the Delta opioid receptor (DOR), in opioid-induced respiratory depression in the ventral respiratory group (VRG) is largely unknown. Here, we sought to determine (1) the relationship between DOR-immunoreactive (ir) boutons, bulbospinal and functionally identified respiratory neurons in the VRG and (2) the effects of microinjection of the selective DOR agonist, D-Pen 2,5-enkephalin (DPDPE), into different subdivisions of the VRG, on phrenic nerve discharge and mean arterial pressure. Following injections of retrograde tracer into the spinal cord or intracellular labelling of respiratory neurons, in Sprague-Dawley rats, brainstem sections were processed for retrograde or intracellular labelling and DOR-ir. ⋯ DPDPE depressed phrenic nerve amplitude, with little effect on phrenic nerve frequency in the Bötzinger complex, pre-Bötzinger complex and rVRG, the greatest effects occurring in the Bötzinger complex. The results indicate that the DOR is located on afferent inputs to respiratory neurons in the VRG. Activation of the DOR in the VRG is likely to inhibit the release of neurotransmitters from afferent inputs that modulate the pattern of activity of VRG neurons.
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The pathology of Alzheimer's disease includes amyloid-beta peptide aggregation that contributes to degeneration of cholinergic neurons. Even though the underlying molecular mechanisms remain unclear, recent in vitro evidence supports a protective role for estrogens against several neurotoxic agents. Here we report that, in a murine cholinergic cell line (SN56), the massive cell death induced by 1-40 fragment of amyloid-beta peptide was prevented by 17beta-estradiol through a mechanism that may involve estrogen receptor activation. ⋯ However, the receptor was consistently observed also at the nuclear region after estrogen exposure. Overall, these data suggest that estrogen may exert neuroprotective effects against amyloid-beta-induced toxicity by activation of estrogen receptor-mediated pathways. In addition, intracellular estrogen receptors are up-regulated by their cognate hormone even during exposure to neurotoxic agents.
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Orexins (OXs) regulate sleep with possible interactions with brain noradrenergic neurons. In addition, noradrenergic activity affects barbiturate anesthesia. As we have also recently reported that OXs selectively evoke norepinephrine release from rat cerebrocortical slices we hypothesized that barbiturate anesthesia may result from of an interaction with central orexinergic systems. ⋯ A GABAA antagonist, bicuculline, did not modify the inhibitory effects of thiopental and the GABAA agonist, muscimol, did not inhibit norepinephrine release. In addition there was no interaction of barbiturates with either OX1 or OX2 receptors. Collectively our data suggest that orexinergic neurons may be an important target for barbiturates, and GABAA, OX1 and OX2 receptors may not be involved in this interaction.