Neuroscience
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The present study was to determine how afferents from the substantia nigra pars reticulata (SNr) of the basal ganglia to the pedunculopontine tegmental nucleus (PPN) in the brainstem could contribute to the control of behavioral states. We used anesthetized and acutely decerebrated cats (n=22). Repetitive electrical stimulation (10-100 Hz, 20-50 microA, for 4-20 s) to the ventrolateral part of the PPN produced rapid eye movement (REM) associated with a suppression of postural muscle tone (REM with atonia). ⋯ On the other hand, an injection of muscimol into the dorsolateral part of the SNr (1-15 mM, 0.1-0.25 microl) induced REM with atonia, which was in turn eliminated by a further injection of muscimol into the PPN (5-10 mM, 0.2-0.25 microl). These results suggest that a GABAergic projection from the SNr to the PPN could be involved in the control of REM with atonia, signs which indicate REM sleep. An excessive GABAergic output from the basal ganglia to the PPN in parkinsonian patients may induce sleep disturbances, including a reduction of REM sleep periods and REM sleep behavioral disorders (REM without atonia).
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Comparative Study
N-acetylaspartate levels of left frontal cortex are associated with verbal intelligence in women but not in men: a proton magnetic resonance spectroscopy study.
The left frontal cortex plays an important role in executive function and complex language processing inclusive of spoken language. The purpose of this work was to assess metabolite levels in the left and right prefrontal cortex and left anterior cingulum by proton magnetic resonance spectroscopy and relate results to verbal intelligence (Wechsler Adult Intelligence Scale revised) in a sample of college-educated healthy volunteers (dorsolateral prefrontal cortex [DLPFC]: n=52, 23 females, and left anterior cingulum: n=62, 22 females; age range: 20-75 years). In women only, N-acetylaspartate in the DLPFC and in the left anterior cingulate cortex was positively correlated with vocabulary scores. Our data support the hypothesis of existing gender differences regarding the involvement of the left frontal cortex in verbal processing as reflected in different correlations of specific metabolites with verbal scores.
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Comparative Study
The diurnal rhythm of adenosine levels in the basal forebrain of young and old rats.
There are significant decrements in sleep with age. These include fragmentation of sleep, increased wake time, decrease in the length of sleep bouts, decrease in the amplitude of the diurnal rhythm of sleep, decrease in rapid eye movement sleep and a profound decrease in electroencephalogram Delta power (0.3-4 Hz). Old rats also have less sleep in response to 12 h-prolonged wakefulness (W) indicating a reduction in sleep drive with age. ⋯ In experiment 2, old rats kept awake for 6 h (first half of lights-on period) accumulated more AD compared with young rats. If old rats have more AD then why do they sleep less? To investigate whether changes in sensitivity of the AD receptor contribute to the decline in sleep, experiments 3 and 4 determined that for the same concentration of AD or the AD receptor 1 agonist, cyclohexyladenosine, old rats have less sleep compared with young rats. We conclude that even though old rats have more AD, a reduction in the sensitivity of the AD receptor to the ligand does not transduce the AD signal at the same strength as in young rats and may be a contributing factor to the decline in sleep drive in the elderly.
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Comparative Study
Differential effects of testosterone on protein synthesis activity in male and female quail brain.
In Japanese quail, testosterone (T) increases the Nissl staining density in the medial preoptic nucleus (POM) in relation to the differential activation by T of copulatory behavior. The effect of T on protein synthesis was quantified here in 97 discrete brain regions by the in vivo autoradiographic (14)C-leucine (Leu) incorporation method in adult gonadectomized male and female quail that had been treated for 4 weeks with T or left without hormone. T activated male sexual behaviors in males but not females. ⋯ The POM boundaries were defined by a denser Leu incorporation than the surrounding area and incorporation was increased by T more in males (25%) than in females (6%). These results confirm that protein synthesis in brain areas relevant to the control of sexual behavior can be affected by the sex of the subjects or their endocrine condition and that T can have differential effects in the two sexes. These anabolic changes should reflect the sexually differentiated neurochemical mechanisms mediating behavioral activation.
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Stress and stress-related hormones induce structural changes in neurons of the adult CNS. Neurons in the hippocampus, the amygdala and the prefrontal cortex undergo neurite remodeling after chronic stress. In the hippocampus some of these effects can be mimicked with chronic administration of adrenal steroids. ⋯ While chronic stress increases the number of PSA-NCAM- and DCX-immunoreactive cells in the piriform cortex layer II, chronic corticosterone administration decreases these numbers. These findings indicate that stress and adrenal steroids affect the piriform cortex and suggest that in this region, as in the hippocampus, they may induce structural changes. This is a potential mechanism by which stress and corticosterone modulate functions of this limbic region, such as its participation in olfactory memory.