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Pontine noradrenergic neurons of the locus coeruleus (LC) and sub-coeruleus (SubC) region cease firing during rapid eye movement sleep (REMS). This plays a permissive role in the generation of REMS and may contribute to state-dependent modulation of transmission in the central nervous system. Whether all pontomedullary catecholaminergic neurons, including those in the A1/C1, A2/ C2 and A7 groups, have REMS-related suppression of activity has not been tested. We used Fos protein expression as an indirect marker of the level of neuronal activity and linear regression analysis to determine whether pontomedullary cells identified by tyrosine hydroxylase (TH) immunohistochemistry have reduced Fos expression following REMS-like state induced by pontine microinjections of a cholinergic agonist, carbachol in urethane-anesthetized rats. The percentage of Fos-positive TH cells was negatively correlated with the cumulative duration of REMS-like episodes induced during 140 min prior to brain harvesting in the A7 and rostral A5 groups bilaterally (p<0.01 for both), and in SubC neurons on the side opposite to carbachol injection (p<0.05). Dorsal medullary A2/C2 neurons did not exhibit such correlation, but their Fos expression (and that in A7, rostral A5 and SubC neurons) was positively correlated with the duration of the interval between the last REMSlike episode and the time of sacrifice (p<0.05). In contrast, neither of these correlations was significant for A1/C1 or caudal A5 neurons. These findings suggest that, similar to the prototypic LC neurons, neurons of the A7, rostral A5 and A2/C2 groups have reduced or abolished activity during REMS, whereas A1/C1 and caudal A5 neurons do not have this feature. The reduced during REMS activity in A2/C2, A5 and A7 neurons, and the associated decrements in norepinephrine release, may cause state-dependent modulation of transmission in brain somato-and viscerosensory, somatomotor, and cardiorespiratory pathways.Keywords autonomic regulation; brainstem; locus coeruleus; motor control; norepinephrine *Corresponding author: Irma Rukhadze, Ph.D., Department of Animal Biology 209E/VET, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6046, USA, Tel. +215-898-6489, Fax. +215-573-5186 E-mail: rukhadze@vet.upenn.edu (I. Rukhadze). Suggested Neuroscience Section Editor (Systems Neuroscience): Dr. Miles Herkenham, NIMH, Section on Functional Neuroanatomy, Bldg. 36, Rm. 2D15, 36, Convent Dr., MSC 4070, Bethesda, MD 20892-4070, USA.Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Ac...

Background: Obstructive sleep apnea (OSA) is associated with glucose intolerance. Both chronic sleep disruption and recurrent blood oxygen desaturations (chronic–intermittent hypoxia, CIH) may cause, or exacerbate, metabolic derangements. Methods: To assess the impact of CIH alone, without accompanying upper airway obstructions, on the counter-regulatory response to glucose load and cardiorespiratory parameters, we exposed adult male Sprague-Dawley rats to CIH or sham room air exchanges for 10 h/day for 7, 21, or 35 days and then, 1 day after conclusion of CIH exposure, conducted intravenous glucose-tolerance tests (ivgtt) under urethane anesthesia. Additional rats underwent 35 days of CIH followed by 35 days of regular housing, or had 35 day-long CIH exposure combined with daily administration of the type 1 angiotensin II receptor antagonist, losartan (15 mg/kg, p.o.), and then were also subjected to ivgtt. Results: Compared with the corresponding control groups, CIH rats had progressively reduced glucose-stimulated insulin release and impaired glucose clearance, only mildly elevated heart rate and/or arterial blood pressure and slightly reduced respiratory rate. The differences in insulin release between the CIH and sham-treated rats disappeared in the rats normally housed for 35 days after 35 days of CIH/sham exposure. The losartan-treated rats had improved insulin sensitivity, with no evidence of suppressed insulin release in the CIH group. Conclusion: In adult rats, the glucose-stimulated insulin release is gradually suppressed with the duration of exposure to CIH, but the effect is reversible. Elimination of the detrimental effect of CIH on insulin release by losartan suggests that CIH disrupts glucoregulation through angiotensin/catecholaminergic pathways. Accordingly, treatment with continuous positive airway pressure may ameliorate pre-diabetic conditions in OSA patients, in part, by reducing sympathoexcitatory effects of recurrent nocturnal hypoxia.

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Whole-body vibration (WBV) has been linked to chronic back pain but the mechanisms of its development are unknown, as is how biomechanical contributions modulate the pain response. An animal model of WBV was developed in which rats were exposed to 7 days of either 5Hz or 15Hz vibration. WBV induced immediate sensitivity (i.e. pain) that was sustained for 7 days after the cessation of the WBV exposure. There was no difference in the pain response between the two vibration frequencies. Increases in the inflammatory mediator, COX-2, were also induced following painful WBV in the lumbar spinal cord, suggesting a potential mechanism for the chronic pain.