Anabel Jiménez-Anguiano

Manipulations during forced wakefulness have differential impact on sleep architecture, EEG power spectrum, and Fos induction.

We propose a hypothesis suggesting that the most prominent experiences occurring during wakefulness activate specific clusters of neurons related to such experiences. These neurons could possibly then evoke the release of various types of sleep-inducing molecules, thereby causing different patterns of sleep architecture. In this study, we therefore sought to determine whether manipulations of behavior during wakefulness, such as forced wakefulness induced by gentle handling, forced wakefulness associated with a stressful condition such as immobilization, or forced wakefulness associated with excess intake of palatable food, could result in a variation of Fos immunoreactivity in selective brain structures and could also result in different sleep and EEG power density patterns. The results showed that the sleep-wake cycle of rats after all the experimental manipulations was different not only with respect to the control group but also among themselves. Additionally, power spectrum analysis showed an increase of 0.25-4.0 Hz in all experimental manipulations, whereas the 4.25-8.0 Hz increase occurred only in the situation of forced wakefulness plus stress. The Fos induction showed activation of cell clusters in cortical areas and telencephalic centers, in several hypothalamic nuclei, in monoaminergic cell groups, and in brain stem nuclei. The density of Fos-immunoreactive neurons varied in relation to the different paradigms of forced wakefulness. These results suggest that activation of cell clusters in the brain are related to the type of manipulation imposed on the rat during wakefulness and that such variation in cell activation prior to sleep may be associated with sleep architecture and EEG power.

Cortistatin modulates memory processes in rats.

Cortistatin (CST) is a recently described neuropeptide with high structural homology with somatostatin. Its mRNA is restricted to gamma amino butyric acid (GABA)-containing cells in the cerebral cortex and hippocampus. CST modulates the electrophysiology of the hippocampus and cerebral cortex of rats; hence, it may be modulating mnemonic processes. In this study, we have evaluated the effect of CST and somatostatin (SS) on short- and long-term memory (STM and LTM, respectively), as well as on the extinction of the behavior by using the footshock passive avoidance behavioral test. In addition, we tested the ability of both neuropeptides to affect the generation of cAMP in hippocampal neurons in culture. Results showed that the administration of either CST or SS into the hippocampal CA1 deteriorates memory consolidation in a dose-response fashion and facilitates the extinction of the learned behavior. CST was more potent than SS. Likewise, CST increases cAMP while SS decreases it. These results strongly support a modulatory role for CST in memory processes.

Brain distribution of vasoactive intestinal peptide receptors following REM sleep deprivation.

Vasoactive intestinal peptide (VIP) has been shown to increase rapid eye movement (REM) sleep in normal and insomniac animals, while the administration of anti-VIP antibodies or an antagonist of VIP receptors decreases REM sleep. In addition, recently, it has been suggested that a VIP-like substance accumulates in the CSF during waking and that it may be involved in the production of the REM rebound normally seen following REM sleep deprivation. This evidence suggests that VIP may be important in modulating REM sleep in normal conditions and during REM sleep rebound. To determine whether VIP is involved in REM sleep homeostasis, VIP receptors of discrete brain areas was determined by autoradiography after 24 and 72 h of REM sleep deprivation (REM SD) by the water tank technique. Since this procedure has been suggested to produce some stress, an additional group adapted for 7 days to the sleep deprivation situation was tested. The results showed that REM SD produces an increase in the density of VIP receptors in several brainstem and forebrain structures at 24 h of REM SD and more so at 72 h of REM SD. Interestingly, results showed that habituation to the REM SD procedure decreases the density of VIP receptors in some areas of the brain of the REM sleep-deprived rats. The results are discussed in terms of the possibility that waking induces an increase of VIP receptors in several structures, which in turn are responsible for modulating REM sleep, but that stress contributes in part to VIP receptor changes.

The Combination of VIP and Atropine Induces REM Sleep in Cats Rendered Insomniac by PCPA

Twenty-four cats were implanted with electrodes for chronic sleep recordings. One week after the surgery, cats were treated with two intraperitoneal injections of parachlorophenylalanine (PCPA), an inhibitor of serotonin synthesis, to induce insomnia. Twenty-four hours after the second injection of PCPA, cats were at the peak of insomnia (strong reduction of both slow wave sleep 2 and rapid-eye movement [REM] sleep). During this period cats were divided into four groups (n = 6) and were injected with either atropine (0.5 mg/kg, IM [3.5 mmol/kg]), vasoactive intestinal peptide (VIP) (200 ng, ICV [60 pmol]) or atropine plus VIP (same doses and routes of administration). The control group received saline intramuscularly (IM) intracerebroventricularly and (ICV). Results showed that VIP and atropine injected alone and in combination increased mean total time of REM sleep in PCPA-treated animals. These findings are discussed in terms of a serotonin-acetylcholine interaction.

Effects of biperiden on sleep at baseline and after 72 h of REM sleep deprivation in the cat.

We examined the effects of the muscarinic M1 antagonist biperiden in cats. In the first experiment a dose-response analysis was performed with intraventricular injection (IV ventricle) of biperiden. In the second experiment after REM sleep deprivation cats were injected with either biperiden (0.1 mg/kg) or saline. Biperiden produced a reduction in REM sleep percentage and an increase in REM sleep latency with these high doses. The 0.1 mg/kg biperiden dose, which did not suppress REM sleep at baseline, did reduce the REM sleep rebound. The present study suggests a modulatory role of biperiden on REM sleep regulatory processes. The fact that an effect of biperiden is noted only at the high doses suggests that at these doses the drug is influencing non-M1 receptors. Changes in the sensitivity of these receptors as a result of REM sleep deprivation might explain why a dose of biperiden will reduce REM sleep rebound, while being ineffective in suppressing REM sleep at baseline.

Rapid eye movement (REM) sleep deprivation in 6-OHDA nigro-striatal lesioned rats with and without transplants of dissociated chromaffin cells

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. Rats with 6-OHDA lesions were subjected to 24 or 72 h of REM sleep deprivation and tested with various doses of apomorphine to determine turning behavior frequencies. At end of those experiments, the animals were transplanted with dissociated chromaffin cells and turning behavior was tested again. 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 Parkinsons disease through the DA system.

Chloramphenicol prevents carbachol-induced REM sleep in cats

Twenty-four cats were implanted for chronic sleep recordings. One week after the surgery, cats were divided into four groups. Two groups were treated with three i.p. injections of 150 mg/kg chloramphenicol (CAP) separated by 12 h. Carbachol (8 micrograms/1 microliter) or saline (1 microliter) was injected into the pontine reticular formation (PRF) 1 h after the last injection of CAP. The other two groups received saline or carbachol into the PRF without CAP pre-treatment. Polygraphic recordings were started immediately after the microinjection and lasted 11 h. Carbachol increased REM sleep (P < 0.001) and reduced SWS2 (P < 0.05). In contrast, chloramphenicol reduced REM sleep (P < 0.001) and increased SWS2 (P < 0.01). The combination of these drugs increased wakefulness (P < 0.01) and reduced both SWS2 and REM sleep (P < 0.001). This data shows that chloramphenicol prevents carbachol induced REM sleep. Results are discussed in terms of an interaction between brain proteins and the cholinergic system to induce REM.