Neuroscience
-
Comparative Study
Sleep-waking discharge profiles of median preoptic and surrounding neurons in mice.
The median preoptic nucleus (MnPO), part of the anteroventral third ventricular region, plays a key role in body fluid homeostasis and cardiovascular regulation. Recently, a cluster of neurons showing sleep-related c-fos immunoreactivity was found in the rat MnPO, and a subsequent electrophysiological study found that nearly 76% of rat MnPO neurons exhibit increased discharge during sleep. In a recent single unit recording study in mice, we found that sleep-active neurons are not localized in any specific region of the preoptic/basal forebrain (POA/BFB). ⋯ Only slowly discharging (<5 Hz) slow-wave sleep (SWS)/PS-selective neurons were found in the MnPO. During the transition from W to SWS, all of these SWS/PS-selective neurons fired not before, but after, sleep onset, with a gradual increase in discharge rate. In addition to its well-known homeostatic and cardiovascular functions, the MnPO might modulate the sleep-waking cycle by playing different roles in sleep/wake state regulation.
-
Circadian rhythms are physiological and behavioral oscillations that have period lengths of approximately 24 h. In mammals, circadian rhythms are driven by a master pacemaker in the hypothalamic suprachiasmatic nucleus (SCN). These rhythms can be entrained to light:dark cycles through photic and non-photic cues. ⋯ Ex vivo data showed that the PER2::LUC peaks in SCN and peripheral tissues were closely linked to time of activity onset in both groups. Thus, this wheel restriction protocol is capable of reducing and in some cases apparently hindering photic re-entrainment of the circadian system, verifying this protocol as a mechanism for study of photic/non-photic entrainment interactions. Our results suggest that LD inversion under dim light and a wheel-restriction protocol does not induce internal desynchrony, indicating that slowing the rate of shift by limiting both entrainment inputs may induce less "jet lag".
-
The rapid detection of sensory changes is important to survival. The change-detection system should relate closely to memory since it requires the brain to separate a new stimulus from past sensory status. To clarify effects of past sensory status on processing in the human somatosensory cortex, brain responses to an abrupt change of intensity in a train of electrical pulses applied to the hand were recorded by magnetoencephalography (MEG). ⋯ The abrupt change in stimulus intensity activated the contralateral primary (cSI) and secondary somatosensory cortex (cSII). The amplitude of the cSI and cSII activity was dependent on not only the magnitude of the change in intensity but also the length of the conditioning stimulus prior to the change, suggesting that storage of prior tactile information was involved in generating these responses. The possibility that an activity of onset (with no conditioning stimulus) would be involved in the change-related activity was also discussed.
-
The spontaneous and event-related firing activity of the medial prefrontal cortex (mPFC) pyramidal neurons are modulated mainly by glutamatergic inputs and GABAergic afferents. Substantial data demonstrate that α(2)-adrenoceptors also play specific roles in the regulation of the firing of these pyramidal neurons. In the present study, the effects of α(2)-adrenoceptor agents on spontaneous, GABA- and glutamate-mediated firing of mPFC pyramidal neurons were examined in anaesthetized rats. ⋯ Clonidine with low current intensity (2-5 nA) did not significantly modulate the excitatory effect of glutamate ejection on firing rate of the pyramidal neurons for both the absolute effect and the percentage of excitation. In contrast, the absolute excitatory effect of glutamate was not significantly strengthened in the presence of clonidine with high current intensity (20-40 nA) but the percentage of excitation by glutamate was increased. These results indicate that the inhibitory effects of NE on spontaneous firing of the mPFC pyramidal neurons are mediated by α(2)-adrenoceptors, whereas α(2)-adrenoceptors stimulation enhanced GABA-mediated inhibition and play a specific part in modulation of glutamate-mediated excitation on the neurons.
-
Comparative Study
Increased expression of sonic hedgehog in temporal lobe epileptic foci in humans and experimental rats.
Sonic hedgehog (Shh) is a soluble signaling protein that is crucial in regulating cell proliferation, migration and differentiation, axonal guidance and neural progenitor cell survival during nervous system development. Recent evidence suggests that the Shh plays an important role in adulthood in regulating structural plasticity. Here we investigated the expression of Shh in temporal lobe epileptic foci in patients and experimental animals in order to explore the probable relationship between Shh expression and temporal lobe epilepsy (TLE). ⋯ Compared to the control group, Shh expression was enhanced in the temporal neocortex of patients with intractable TLE. In experimental rats, Shh expression gradually increased from 7 to 60 days post-seizure in temporal neocortex and elevated from 3 to 60 days in hippocampus with the peak levels at 30 days as compared with the control group. These results suggest that Shh may play an important role in the development of TLE.