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In the adult rat, exposure to intermittent hypoxia (IH), such as occurs in sleep-disordered breathing, is associated with neurobehavioral impairments and increased apoptosis in the hippocampal CA1 region and cortex. We hypothesized that the episodic hypoxic-reoxygenation cycles of IH would induce oxidant stress, and the latter may underlie the IH-associated spatial learning and retention deficits. Adult male rats were therefore exposed to IH (90-second alternations of 10% oxygen and 21% oxygen) or room air (RA) for 7 days, and received twice-daily injections of either 3 mg/kg of the antioxidant PNU-101033E (PNU) or vehicle (V). Rats were then trained in a standard place-training task in the water maze. V-IH displayed significant impairments of spatial learning in the water maze, which were attenuated by PNU-101033E. Post hoc analyses further revealed that V-IH had significantly longer latencies and pathlengths to locate the hidden platform than PNU-IH, V-RA, or PNU-RA, indicating that PNU-101033E treatment reduced the behavioral impairments associated with IH. In addition, treatment with PNU-101033E markedly attenuated the increase in lipid peroxidation, and isoprostane concentrations associated with exposure to IH. Collectively, these findings indicate that the IH exposure is associated with increased oxidative stress, which is likely to play an important role in the behavioral impairments observed in a rodent model of sleep-disordered breathing.

Financial Disclosure: Drs Kheirandish and Gozal are the recipients of an investigator-initiated grant from Astra Zeneca Ltd for an unrelated research project on the effect of intranasal budesonide in mild sleepdisordered breathing in children. Dr Gozal serves on the national speaker bureau of Merck. ABSTRACTOBJECTIVE. Tonsillectomy and adenoidectomy (T&A) is the primary therapeutic approach for sleep-disordered breathing (SDB) in children. However, residual mild SDB will be found in more than one third of these patients after T&A. We hypothesized that combined therapy with the leukotriene receptor antagonist montelukast and intranasal budesonide would result in normalization of residual SDB after T&A.METHODS. During the period of October 2002 to February 2005, children who underwent T&A for SDB underwent a routine postoperative (second) overnight polysomnographic evaluation (PSG) 10 to 14 weeks after T&A surgery. In children with residual apnea hypopnea index (AHI) Ͼ1 and Ͻ5/hour of total sleep time (TST), treatment with montelukast and intranasal budesonide aqueous solution was administered for a period of 12 weeks (M/B group), at which time a third PSG was performed. Children who had residual SDB and did not receive M/B therapy from their treating physicians were recruited as control subjects.RESULTS. Twenty-two children received M/B, and 14 children served as control subjects. Mean age, gender distribution, ethnicity, and BMI were similar in the 2 treatment groups. The mean AHI at the second PSG was 3.9 Ϯ 1.2/hour of TST and 3.6 Ϯ 1.4/hour of TST in M/B-treated and control patients, respectively. Similar nadir arterial oxygen saturation (87.3 Ϯ 1.2%) and respiratory arousal index (4.6 Ϯ 0.7/hour of TST) were recorded for both groups. However, the M/B group demonstrated significant improvements in AHI (0.3 Ϯ 0.3/hour of TST), in nadir arterial oxygen saturation (92.5 Ϯ 3.0%), and in respiratory arousal index (0.8 Ϯ 0.7/hour of TST) on the third PSG, whereas no significant changes occurred over time in control subjects.CONCLUSIONS. Combined anti-inflammatory therapy that consists of oral montelukast and intranasal budesonide effectively improves and/or normalizes respiratory and sleep disturbances in children with residual SDB after T&A. O BSTRUCTIVE SLEEP APNEA and sleep-disordered breathing (SDB) is a common and highly prevalent disorder in the pediatric age range that affects 2% to 3% of all children. 1 When left untreated, SDB is associated with substantial morbidity, primarily affecting neurobehavioral and cardiovascular systems. 2-9 Thus, because in otherwise normal children SDB is attributed primarily to adenotonsillar hypertrophy, 10,11 tonsillectomy and adenoidectomy (T&A) is currently the most common treatment for children with SDB. 12 However, although a recent meta-analysis of the published literature suggested a relatively high success rate for T&A, averaging ϳ85%, 13 the overall short-term cure rates for this surgical procedure in otherwise healthy children may not be as favorable as previously an...

Obstructive sleep apnea (OSA) is a frequent medical condition and is associated with cognitive impairments in adults and with hyperactivity and decreased school performance in children. In an adult rodent model, intermittent hypoxia (IH), such as occurs in OSA, is associated with neurodegenerative changes in the hippocampus and cortex and with spatial learning deficits. Because a unique developmental window of neural vulnerability to IH is present, we hypothesized that exposure to IH throughout the vulnerable ages would result in increased behavioral impairments in the juvenile rat. Rat pups were therefore exposed to either room air or IH beginning at postnatal (PN) d 10 until PN d 30. Learning and memory were assessed via a standard place-training version of the Morris water maze beginning at PN d 25. Locomotor activity was assessed on PN d 29 and 30. Pups exposed to IH displayed significant spatial learning impairments, and exposed male rats but not female rats displayed increased locomotor activity in the open field. Collectively, these findings indicate that exposure to IH at an age that corresponds to the peak incidence of OSA in children induces substantial learning impairment and gender-dependent behavioral hyperactivity in the juvenile rat. We postulate that this novel experimental model may allow for future exploration of mechanisms underlying the neurobehavioral deficits of children with OSA.

No abstract

Intermittent hypoxia (IH) during sleep, a critical feature of sleep apnea, induces significant neurobehavioral deficits in the rat. Cyclooxygenase (COX)-2 is induced during stressful conditions such as cerebral ischemia and could play an important role in IH-induced learning deficits. We therefore examined COX-1 and COX-2 genes and COX-2 protein expression and activity (prostaglandin E2 [PGE2] tissue concentration) in cortical regions of rat brain after exposure to either IH (10% O2 alternating with 21% O2 every 90 seconds) or sustained hypoxia (10% O2). In addition, the effect of selective COX-2 inhibition with NS-398 on IH-induced neurobehavioral deficits was assessed. IH was associated with increased COX-2 protein and gene expression from Day 1 to Day 14 of exposure. No changes were found in COX-1 gene expression after exposure to hypoxia. IH-induced COX-2 upregulation was associated with increased PGE2 tissue levels, neuronal apoptosis, and neurobehavioral deficits. Administration of NS-398 abolished IH-induced apoptosis and PGE2 increases without modifying COX-2 mRNA expression. Furthermore, NS-398 treatment attenuated IH-induced deficits in the acquisition and retention of a spatial task in the water maze. We conclude that IH induces upregulation and activation of COX-2 in rat cortex and that COX-2 may play a role in IH-mediated neurobehavioral deficits.

Exposure to intermittent hypoxia (IH), such as occurs in sleep-disordered breathing, is associated with increased apoptosis in vulnerable brain regions as well as with spatial reference memory deficits in adult and developing rats. The latter are more susceptible to IH, suggesting that early exposure to IH may have long-term consequences. Rats were exposed to 14 d of room air (RA) or IH starting at postnatal d 10. Working memory was then assessed in the water maze at 4 mo of age using a delayed matching to place task in which the rats were required to locate a submerged platform hidden in a novel location on the first trial (T1 or acquisition trial), and then remember that position after a delay (T2 or test trial). Mean escape latencies and swim distances were derived and the savings (T1-T2) were used as a measure of working memory. Male but not female rats exposed to IH showed working memory deficits at both a 10-and 120-min delay (for both latency and pathlength). Additionally, Sholl analysis of Golgi-stained neurons revealed decreased dendritic branching in the frontal cortex, but not the hippocampus, of male rats exposed to IH. Norepinephrine concentrations, dopamine turnover, and tyrosine hydroxylase activity were increased similarly in males and females. However, increased dopamine concentrations were present only in the frontal cortex of female rats. In conclusion, exposure to IH during a critical developmental period is associated with long-term alterations in frontal cortical dopaminergic pathways that may underlie gender differences in neurobehavioral deficits. OSA is a highly prevalent condition that affects 2-3% of all children (1-3). It is characterized by the repetitive development of either complete or partial upper airway occlusion that leads to periodic hypoxemia and hypercapnia and to recurring arousals. In recent years, it has become apparent that OSA imposes substantial neurobehavioral morbidity (4 -6), particularly of functions pertaining to the PFC (7), and that such alterations in attention, executive, and intellectual function may not be completely reversible (8). The recent development of a rodent model, whereby IH is applied during sleep, has allowed for improved delineation of some of the potential mechanisms underlying the morbid consequences of OSA (8 -17). Furthermore, a unique period of neuronal susceptibility emerged, such that developing rats exposed to IH displayed reduced apoptosis during the immediate postnatal period but markedly enhanced neuronal cell loss between 10 and 25 d of age, compared with adult animals (18). Furthermore, exposure to IH during this period was associated with marked reductions in the ability to acquire a spatial task in the water maze and with locomotor hyperactivity in males but not in females (9). The potential irreversibility of the IH-induced effects was further suggested by Decker and colleagues (19), who reported altered dopaminergic transmission in rats exposed perinatally

Obstructive sleep apnea (OSA) is a frequent medical condition characterized by intermittent hypoxia (IH) during sleep, and is associated with neurodegenerative changes in several brain regions along with learning deficits. We hypothesized that aging rats exposed to IH during sleep would be particularly susceptible. Young (3-4 months) and aging (20-22 months) Sprague-Dawley rats were therefore exposed to either room air or IH for 14 days. Learning and memory was assessed with a standard place-training version of the Morris water maze. Aging rats exposed to room air (RA) or IH displayed significant spatial learning impairments compared with similarly exposed young rats; furthermore, the decrements in performance between RA and IH were markedly greater in aging compared with young rats (p < 0.01), and coincided with the magnitude of IH-induced decreases in cyclic AMP response element binding (CREB) phosphorylation. Furthermore, decreases in proteasomal activity occurred in both young and aging rats exposed to IH, but were substantially greater in the latter (p < 0.001). Neuronal apoptosis, as shown by cleaved caspase 3 expression, was particularly increased in aging rats exposed to IH (p < 0.01 versus young rats exposed to IH). Collectively, these findings indicate unique vulnerability of the aging rodent brain to IH, which is reflected at least in part, by the more prominent decreases in CREB phosphorylation and a marked inability of the ubiquitin-proteasomal pathway to adequately clear degraded proteins.