Brain research
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Previously, we reported that paradoxical sleep (PS) is sexually dimorphic in mice and rats. Since some early studies indicate that PS is suppressed during proestrus night, it is important to know whether the estrus cycle and accompanying circulating ovarian hormones could explain the sexual dimorphism of PS. To examine this, sleep patterns of male rats were compared with those of normal cycling female rats and ovariectomized females in a 12:12 h light/dark cycle. ⋯ In sum, normal cycling females show no change in daytime sleep patterns across the estrus cycle, but have significantly less PS during proestrus nights than during metestrus and diestrus nights. The results indicate that the sex difference in nighttime PS is due to the suppression of PS by ovarian hormones during proestrus and, to a less extent, estrus nights. The sex difference in daytime PS, on the other hand, appears to be independent of circulating ovarian hormones.
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Endothelin-1 (ET-1) has been implicated in hematoma-induced cerebral vasoconstriction and modification of cerebral microvascular reactivity, particularly attenuation of vasodilation to cAMP-dependent dilators and enhanced vasoconstriction to ET-1. We examined effects of the ET-1 antagonist, BQ-123, on hematoma-induced modification of pial arteriolar responses to ET-1 and iloprost, a cAMP-dependent dilator, in vivo, plus the effects of such treatment on the cortical CSF cAMP. Closed cranial windows were implanted in alpha-chloralose anesthetized piglets 4 days following cortical subarachnoid injection of: (1) artificial cerebrospinal fluid (aCSF); (2) autologous blood; (3) BQ-123 alone; or (4) BQ-123 in combination with blood. ⋯ Thus, cerebral hematoma appears to attenuate iloprost-induced dilation and reduce basal cAMP level 4 days following hematoma via release that involves ET-1 of substance(s) on day 1 of hematoma. This substance(s) may act by inhibiting adenylyl cyclase. These results suggest that ET-1 plays an important role in the blood-induced prolonged cerebral vasoconstriction and altered vasoreactivity that follows cerebral hemorrhage via stimulation of ETA receptor.
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Fos protein expression in retinorecipient suprachiasmatic nucleus (SCN) neurons is a marker of photic entrainment of circadian rhythms. Light-induced Fos in neurons of the intergeniculate leaflet (IGL) is not well-characterized. ⋯ In contrast with light-induced Fos in SCN neurons, Fos-IR was observed in the IGL regardless of circadian time. This work supports the idea that the IGL is involved in transmission of photic information to the SCN in rats.
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Since both REM sleep deprivation and unilateral 6-OHDA lesions induce supersensitivity of DA receptors, the purpose of this study was to determine whether the response of rats with such lesions would be modified by REM sleep deprivation. In addition, the effect of grafts of dissociated chromaffin cells was also tested. ⋯ The results showed that REM sleep deprivation nearly doubled the turning behavior frequency, that chromaffin cell grafts decreased it, but that REM deprivation in grafted animals still seemed to produce an increase of post-synaptic supersensitivity independent of denervation. The results were discussed in terms of the possible relationship of sleep with Parkinson's disease through the DA system.
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The purpose of this study was to determine the optimal stimulation site and parameters that result in the greatest changes in cutaneous blood flow during dorsal column stimulation (DCS). Laser Doppler flowmetry was used to assess cutaneous blood flow changes in both rat hindpaws during DCS with a unipolar ball electrode. We found that stimulating the dorsal column at the L2 spinal segment at 0.6 mA at either 25 or 50 Hz with a pulse duration of 0.2 ms resulted in the largest cutaneous blood flow increases in the rat hindpaw. In addition, the DCS response appeared to be limited primarily to the hindpaw ipsilateral to the site of DCS.