Sleep and Behavior in Rats With Pontine Lesions Producing REM Without Atonia
Larry D. Sanford*, Catherine S. Cheng, Amy J. Silvestri, Xiangdong Tang*, Graziella L. Mann, Richard J. Ross and Adrian R. Morrison

Pontine tegmental lesions can eliminate the atonia of rapid eye movement sleep (REM) and allow animals to exhibit overt behavior at the same time that other electrophysiological signs of REM are intact. We produced electrolytic lesions in the reticularis pontis oralis (RPO) and reticularis pontis caudalis (RPC) in rats and observed them for behavior during REM without atonia (REM-A) and for alterations in sleep and waking compared to normal rats. Relatively small unilateral lesions were sufficient to remove the atonia of REM, whereas larger, bilateral lesions were required to release overt behavior during REM-A. Lesions in both RPO and RPC were capable of releasing elaborate behaviors, including full locomotion, during REM-A. The results are discussed with respect to their importance for understanding the neural activity of REM and with respect to REM-A being a model for REM behavior disorder (RBD) in humans.

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Losartan, An Angiotensin AT1 Receptor Antagonist, Modulates Sleep Apnea Expression in Spontaneously Hypertensive (SHR) Rats
David W. Carley, Sinisa M. Trbovic and Miodrag Radulovacki

Spontaneously hypertensive rats (SHR) exhibit frequent sleep-related apnea. The goals of the present study were: 1) to determine if long-term correction of blood pressure (BP) in SHR is associated with sustained apnea suppression, and 2) to correlate changes in apnea expression with changes over time in baroreflex set point and sensitivity. In ten surgically instrumented male SHR, sleep, BP, heart period (HP) and respiration were monitored for six hours per day during a 17-day continuous subcutaneous infusion of losartan, a non-peptide angiotensin II type-1 (AT1) receptor antagonist. Losartan infusion produced sustained significant hypotension (p<0.03) during wakefulness and sleep. HP remained at the baseline level (p>0.8), indicating ongoing baroreflex resetting. Respiratory rate and inspired minute ventilation were unaffected by the infusion (p=0.63 and p=0.65, respectively). Baroreflex sensitivity increased progressively from day 3 to day 17 of infusion. Losartan-induced hypotension was accompanied during non rapid eye movement sleep by decreased spontaneous apnea expression on infusion day 3 (p=0.03), followed by a return toward baseline rates by day 17. Post-sigh apnea expression showed no decrease from baseline, becoming progressively elevated between day 3 and day 17. We conclude that sustained losartan-induced normotension in genetically hypertensive rats is not associated with sustained apnea suppression.

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Infrared Transfer of Electrophysiologic Signals During Magnetic Resonance Imaging
Ronald M. Harper, John M. Parker, Robert C. Frysinger, Luke A. Henderson, Walter del Vecchio and Mary A. Woo

Assessment of electrophysiological signals is essential for determination of states during functional magnetic resonance brain imaging for sleep-related challenges. Such assessment is hindered by introduction of artifacts on the electrophysiological signals by the magnetic fields of the scanner, and, conversely, images can be distorted by contamination from artifacts introduced through metallic signal cables. We describe a low-cost infrared system for transferring electrophysiological signals from amplifiers near magnetic resonance scanners. The system consists of a multi-channel consumer infrared audio system, modified to respond to DC electrophysiological signal levels. The device transmits signals to externally-located receivers through an observation window. The exceptionally low-cost system minimizes induction of noise into magnetic resonance images, and reduces contamination of electrophysiological signals by the scanner.

Comparison of Three Muscarinic Agonists Injected into the Medial Pontine Reticular Formation of Rats to Enhance REM Sleep
Gerald A. Marks and Christian G. Birabil

To gain insight into the subtypes of muscarinic receptors mediating the long lasting increase in REM sleep following microinjection of muscarinic agonists into the medial pontine reticular formation of the rat, multiple 60 nl injections were made utilizing three different muscarinic agonists. All agonists, in a concentration range of 10-6 to 10-2 Molar, increased REM sleep in a dose-related manner with an inverted "U" relationship. The order of potency to increase REM sleep was McN-A-343>oxotremorine-M=carbachol. Based on each agonist's subtype-selective potency in functional assays, oxotremorine-M is the most potent agonist at every subtype. It was therefore concluded that the observed order of potency is not consistent with activation of a single muscarinic receptor. Inasmuch as McN-A-343 acts as a weak, partial agonist and the other ligands full agonists at m3 receptors, we hypothesize that activation of m3 receptors by oxotremorine-M and carbachol antagonizes REM sleep increases and results in their lowered potency. This hypothesis is consistent with preliminary evidence demonstrating that injecting a relatively selective m3 antagonist, p-F-HHSiD, can increase the REM-inducing potency of a low and formerly ineffective dose of oxotremorine-M. A m3 muscarinic receptor mechanism in the pons antagonistic to increasing REM sleep, present in the rat but absent in the cat, may underlie some of the species differences observed in the cholinergic induction of REM sleep.

Hypothalamic Neurons that Contain Hypocretin (Orexin) Express c-fos During Active Wakefulness and Carbachol-induced Active Sleep
Pablo Torterolo, Jack Yamuy, Sharon Sampogna, Francisco R. Morales and Michael H. Chase

Hypothalamic hypocretinergic neurons have been implicated in the control of a variety of behavioral states. However, the activity of these neurons during sleep and wakefulness has not been described. Consequently, we examined Fos immunoreactivity (as a marker of neuronal activity) in hypocretinergic neurons during the following behavioral states: a) quiet wakefulness (QW), wherein the cats were awake and restrained in a head-holder device; b) active wakefulness (AW), wherein the cats were freely exploring a new environment and exhibited almost continuous locomotor activity; and c) carbachol-induced active sleep (AS-carbachol), wherein prolonged periods of active sleep were induced by the microinjection of carbachol into the nucleus pontis oralis. The majority of hypocretinergic neurons expressed c-fos during AW (184.7±19.6, 79%), whereas only a small number of these cells expressed c-fos during QW (3.0±1.9, 2%). Surprisingly, a large portion of the hypocretinergic neurons were Fos immunoreactive during AS-carbachol (60.3±11.0, 34%). The significant difference (p<0.0001) between QW and AW in the number of hypocretinergic neurons that expressed c-fos indicates that these neurons are not involved in the maintenance of wakefulness per se, but more likely to play a role in arousal-type behaviors that accompany locomotor-explorative activity. In addition, the intriguing finding that a larger number of hypocretinergic neurons express c-fos during AS-carbachol than during quiet wakefulness suggests that these neurons play a role in active sleep-related processes.

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Sex Differences in Slow-Wave Activity in Response to Sleep Deprivation
Roseanne Armitage, Carlyle Smith, Sandra Thompson and Robert Hoffmann

A sleep deprivation paradigm was utilized as a means of assessing sex differences in slow-wave sleep regulation. Quantitative EEG activity was evaluated in 16 healthy young adults (8 men and 8 women) during baseline and in recovery sleep after 40 hours of total sleep deprivation. Significant increases in slow-wave activity (SWA) incidence, amplitude and power were evident in the first half of recovery sleep, particularly in the first NREM period. However, sex differences were also evident in SWA response to sleep deprivation. Women showed a more dramatic increase in SWA in comparison to men. This sex difference was robust and evident in both central parietal EEG regardless of whether data were analyzed by NREM period or independent of sleep stage. These findings suggest that slow-wave sleep regulatory mechanisms and associated homeostatic processes may differ between men and women under biological "challenge" conditions.

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