Neuroscience
-
Comparative Study
Progressive changes in cortical state before and after spontaneous arousals from sleep in elderly and middle-aged women.
Arousals are often considered to be events which have an abrupt onset and offset, indicating abrupt changes in the state of the cortex. We hypothesized that cortical state, as reflected in electroencephalograph (EEG) signals, exhibits progressive systematic changes before and after a spontaneous, isolated arousal and that the time courses of the spectral components of the EEG before and after an arousal would differ between healthy middle-aged and elderly subjects. We analyzed the power spectrum and Sample Entropy of the C3A2 EEG before and after isolated arousals from 20 middle-aged (47.2±2.0 years) and 20 elderly (78.4±3.8 years) women using polysomnograms from the Sleep Heart Health Study database. ⋯ Consistent with these findings, Sample Entropy decreased steadily before an arousal, increased markedly during the arousal, and remained above pre-arousal baseline levels for ∼30 s after the arousal. In middle-aged, but not in elderly, women the presence of early pre-arousal low delta power was associated with shorter arousals. We propose that this attenuation of the effect of the arousing stimulus may be related to the slow (<1 Hz) cortical state oscillation, and that prolonged alterations of cortical state due to arousals may contribute to the poor correlation between indices of arousals and indices of sleepiness or impaired cognitive function.
-
Adult mammalian brains are capable of some structural plasticity. Although the basic cellular mechanisms underlying learning and memory are being revealed, extrinsic factors contributing to this plasticity remain unspecified. White-footed mice (Peromyscus leucopus) are particularly well suited to investigate brain plasticity because they show marked seasonal changes in structure and function of the hippocampus induced by a distinct environmental signal, viz., photoperiod (i.e. the number of hours of light/day). ⋯ To investigate the functional consequences of reduced hippocampal size, we examined the effects of photoperiod on spatial learning and memory in the Barnes maze, and on long-term potentiation (LTP) in the hippocampus, a leading candidate for a synaptic mechanism underlying spatial learning and memory in rodents. Exposure to short days for 10 weeks decreased LTP in the Schaffer collateral-CA1 pathway of the hippocampus and impaired spatial learning and memory ability in the Barnes maze. Taken together, these results demonstrate a functional change in the hippocampus in male white-footed mice induced by day length.
-
Comparative Study
A greater role for the norepinephrine transporter than the serotonin transporter in murine nociception.
Norepinephrine and serotonin involvement in nociceptive functions is supported by observations of analgesic effects of norepinephrine transporter (NET) and serotonin transporter (SERT) inhibitors such as amitriptyline. However, the relative contribution of NET and SERT to baseline nociception, as well as amitriptyline analgesia, is unclear. Amitriptyline and morphine analgesia in wild-type (WT) mice and littermates with gene knockout (KO) of SERT, NET or both transporters was conducted using the hotplate and tail-flick tests. ⋯ Furthermore, in the acetic acid writhing test of visceral nociception pronounced hypoalgesia was again found in NET KO mice, but no change in SERT KO mice. As some of these effects may have resulted from developmental consequences of NET KO, the effects of the selective NET blocker nisoxetine and the selective SERT blocker fluoxetine were also examined in WT mice: only nisoxetine produced analgesia in these mice. Collectively these data suggest that NET has a far greater role in determining baseline analgesia, and perhaps other analgesic effects, than SERT in mice.
-
Syntaxin 1A is a membrane protein playing an integral role in exocytosis and membrane trafficking. The superficial dorsal horn (SDH) of the spinal cord, where nociceptive synaptic transmission is modulated, is rich in this protein. We recently reported that peripheral nerve ligation-induced nociceptive responses are considerably enhanced in syntaxin 1A-knockout mice [Takasusuki T, Fujiwara T, Yamaguchi S, Fukushima T, Akagawa K, Hori Y (2007) Eur J Neurosci 26:2179-2187]. ⋯ These results indicate a possible involvement of syntaxin 1A downregulation in the late maintenance phase of peripheral nerve injury-induced allodynia. In addition, syntaxin 1A knockdown by ribonucleic acid interference enhanced the axonal elongation and sprouting of spinal dorsal horn neurons in culture, suggesting that PSNL-induced syntaxin 1A downregulation may result in the rearrangement of the synaptic connections between neurons in the spinal dorsal horn. Taken together, it is possible to conclude that syntaxin 1A might be involved in spinal nociceptive plasticity induced by peripheral nerve injury.
-
Comparative Study
Functional recovery after hematic administration of allogenic mesenchymal stem cells in acute ischemic stroke in rats.
Hematic administration of bone marrow-derived mesenchymal stem cells (MSCs) in acute ischemic stroke may not only be an effective reparative treatment but also a brain protective therapy that improves neurological recovery. Our purpose was to study whether either i.v. or intracarotid (i.c.) administration of allogenic MSCs during the acute phase were effective in improving neurological recovery and decreasing brain damage in an experimental rat model. In a model of permanent middle cerebral artery occlusion (pMCAO), we analyzed: neurological evaluation; MSCs migration and implantation; interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels; lesion volume; cell death; cellular proliferation; vascular endothelial growth factor (VEGF) expression and blood vessel number. ⋯ MSCs group than in the i.c. control group and blood vessel number was significantly higher in treated groups than control groups with significant differences in the peri-infarct zone at 14 days. We conclude that allogenic MSCs administration shows therapeutic efficacy in our acute ischemic stroke model. Both routes demonstrably improved neurological recovery and provided brain protection.