Neuroscience letters
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Neuroscience letters · Jan 1994
Paradoxical timing of the circadian rhythm of sleep propensity serves to consolidate sleep and wakefulness in humans.
The contribution of the circadian pacemaker and the sleep homeostat to sleep tendency and consolidation was quantified by forced desynchrony of the sleep-wake cycle from the circadian pacemaker in eight men who lived in time-isolation for 33-36 days. Analysis of 175 polygraphically recorded sleep episodes revealed that the circadian pacemaker and the sleep homeostat contribute about equally to sleep consolidation, and that the phase relationship between these oscillatory processes during entrainment to the 24-h day is uniquely timed to facilitate the ability to maintain a consolidated bout of sleep at night and a consolidated bout of wakefulness throughout the day.
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Neuroscience letters · Jan 1994
Streptozotocin-induced diabetes selectively reduces antinociception mediated by mu 1-opioid receptors, but not that mediated by mu 2-opioid receptors.
We assessed the effect of naloxonazine, a selective mu 1-opioid receptor antagonist, on antinociception produced by intrathecal or intracerebroventricular injections of morphine in streptozotocin-induced diabetic mice. The antinociceptive effect of morphine (10 micrograms), administered i.c.v., was significantly less in diabetic mice than in non-diabetic mice. The antinociceptive effect of i.c.v. morphine was significantly reduced in both diabetic and non-diabetic mice following pretreatment with naloxonazine. ⋯ Furthermore, naloxonazine had no significant effect on the antinociceptive effect of i.t. morphine in either diabetic or non-diabetic mice. On the other hand, the antinociceptive effects of i.c.v. and i.t. morphine were significantly reduced following pretreatment with beta-funaltrexamine, a selective mu-opioid receptor antagonist, in both diabetic and non-diabetic mice. In conclusion, mice with diabetes are selectively hyporesponsive to supraspinal mu 1-opioid receptor-mediated antinociception, but are normally responsive to activation of spinal mu 2-opioid receptors.