Obstructive sleep apnea in children with epilepsy: prospective pilot trial.

BACKGROUND: Obstructive sleep apnea (OSA) is prevalent in adults with epilepsy, especially refractory, but limited data exist in children with epilepsy. AIMS: We conducted a prospective pilot study in children with epilepsy to identify the prevalence of OSA and its relationship to the use of antiepileptic drugs (AEDs) and epilepsy types. METHODS: We used Michigan Pediatric Sleep Questionnaire (PSQ) in children with epilepsy. Patients were classified by seizures frequency as mild (0-1 seizure/month) or severe, refractory epilepsy (> 1 seizures/month). We used PSQ ≥ 0.33 as a cutoff point to assess the risk of OSA. RESULTS: Of 84 children, 52 were classified as mild and 32 as severe. Prevalence of OSA was significantly higher in the severe (43.8%) vs the mild group (30.7%, P < 0.05). Children on >1 AED had significantly higher prevalence of OSA (45.8%) than children on ≤1 AED (30.6%, P < 0.05). There was no significant correlation between the prevalence of OSA and seizure types. CONCLUSIONS: OSA is more prevalent in refractory epilepsy and in children who are on multiple AEDs. While further studies are needed to confirm these findings and to assess the consequences of OSA, we believe it is important to screen the children with epilepsy for OSA.

PDGF-beta receptor expression in the dorsocaudal brainstem parallels hypoxic ventilatory depression in the developing rat.

The temporal trajectory of platelet-derived growth factor (PDGF)-beta receptor activation within the dorsocaudal brainstem parallels that of the mild hypoxic ventilatory depression (HVD) seen in adult rats. We hypothesized that enhanced PDGF-beta receptor activity may account for the particularly prominent HVD of developing mammals. To study this issue, 2-, 5-, 10-, and 20-d-old rats underwent hypoxic challenges (10% O(2) for 30 min) after pretreatment with either vehicle (Veh) or the selective PDGF-beta receptor antagonist CGP57148B (intraperitoneal 100 mg/kg). The developmental characteristics and magnitude of the peak hypoxic ventilatory response (HVR) were not modified by the PDGF-beta receptor blocker. However, HVD was markedly attenuated by CGP57148B, and such effect, although still present, gradually abated with increasing postnatal age [p < 0.001, analysis of variance (ANOVA)]. Hypercapnic ventilatory responses were not affected by CGP57148B. The expression of PDGF-beta receptor in the dorsocaudal brainstem was assessed by immunoblotting and confirmed progressively decreasing expression with maturation. We conclude that PDGF-beta receptor activation during hypoxia is an important contributor to HVD at all postnatal ages but more particularly in the immature rat.

Developmental patterns of NF-kappaB activation during acute hypoxia in the caudal brainstem of the rat.

NF-kappaB, an ubiquitous transcription factor which plays a major role in the regulation of stress-related genes, is activated during environmental hypoxia in the dorsocaudal brainstem of adult rats. To examine the developmental pattern of NF-kappaB basal activity in the brainstem and the response to hypoxia, electromobility shift assays and immunohistochemical staining for the P65 subunit of NF-kappaB were performed in caudal brainstem samples of rats at 2, 5, 10, 15, and 60 days postnatal age, following normoxic or hypoxic (1 h in 10% O2) exposures. In addition, the expression of IkappaB-alpha, and IkappaB kinases (ikk)-alpha and -beta was also examined using Western blots. Basal NF-kappaB nuclear activity and nuclear P65 immunoreactivity increased with maturation. In contrast, hypoxia induced enhanced activation of NF-kappaB and nuclear translocation of P65 in youngest animals. Expression of both IkappaB-alpha and ikk-alpha was highest in the more immature rats, and decreased with postnatal age. In contrast, ikk-beta expression was unchanged over time. We conclude that NF-kappaB activity in caudal brainstem is developmentally regulated, and that hypoxia-induced NF-kappaB activation is more prominent in youngest rats. We postulate that postnatal regulation of NF-kappaB complex expression and function may underlie fundamental genomic processes mediating developmental changes in neuronal hypoxic tolerance.

In vivo PDGF beta receptor activation in the dorsocaudal brainstem of the rat prevents hypoxia-induced apoptosis via activation of Akt and BAD.

Activation of platelet-derived growth factor receptor beta (PDGFR) within the caudal brainstem modulates the hypoxic ventilatory response. Since hypoxia does not induce apoptosis in the caudal brainstem, PDGFR could underlie such protective mechanism via a PI3 kinase-dependent phosphorylation of both Akt and BAD pathways. To further study this issue, caudal brainstem lysates were harvested from Sprague--Dawley rats during hypoxia (10% O(2)) after treatment with either vehicle or CGP 57148B (100 mg/kg), a selective blood-brain barrier-permeable PDGFR antagonist. Time-dependent increases in phosphorylated Akt occurred during hypoxia, peaking at 45' and lasting for up to 6 h, without parallel changes in total Akt protein. CGP 57148B attenuated Akt activation at all time points. Similarly, phosphorylation of BAD at serine136 but not at serine 112 occurred in the caudal brainstem as early as 15' of hypoxia, and was completely blocked by CGP 57148B. Furthermore, CGP 57148B treatment elicited significant increases in single-stranded DNA, caspase-like activity, and cleaved caspase 3 after 24 h of hypoxia that were absent in the caudal brainstem of hypoxic vehicle-treated animals. We conclude that PDGFR-dependent in vivo activation of both Akt and BAD during hypoxia prevents induction of apoptosis, and may contribute to the increased hypoxic tolerance of brainstem neurons.

Prenatal cigarette smoke exposure selectively alters protein kinase C and nitric oxide synthase expression within the neonatal rat brainstem.

Maternal smoking is a major risk factor for sudden infant death syndrome. Protein kinase C (PKC) and neuronal nitric oxide synthase (NOS) activities within the dorsocaudal brainstem (DB) mediate critical components of respiratory drive and could be implicated in SIDS. Thus, exposure to smoking during fetal life could modify the expression of these kinases in the DB. Rats were exposed to cigarette smoke or room air (Sham) from day 2 to 22 of pregnancy. Immunoblots of DB lysates at 2 days postnatally revealed no differences in PKC-alpha, PKC-beta, and endothelial NOS expression. However, PKC-gamma, PKC-delta, and neuronal NOS immunoreactivities were reduced in the cigarette smoke group. We conclude that gestational smoking is associated with selective reductions in PKC and NOS isoforms within the DB, which could decrease respiratory drive and lead to enhanced hypoxic vulnerability in infants of smoking mothers.

Passive motion of the extremities modifies alveolar ventilation during sleep in patients with congenital central hypoventilation syndrome.

Passive motion of lower extremities (PMLE) elicits significant increases in alveolar ventilation (V A) in awake children with congenital central hypoventilation syndrome (CCHS), who have absent or near absent ventilatory responses to hypercapnia. We hypothesized that PMLE would improve V A during non-rapid eye movement (NREM) sleep. To study this, six patients with CCHS (0.2 to 7 yr of age) were disconnected from mechanical ventilatory support during Stage III-IV NREM, and their feet were passively moved at the ankle, either manually or with a motorized device strapped to their feet at 40 to 50 strokes/min. Holding of the feet without motion served as control (C). From a total of 74 successful trials not associated with sleep state changes, PET(CO(2)) decreased from 58.9 +/- 3.5 to 40.9 +/- 2.6 mm Hg with PMLE (n = 58; p < 0.001), whereas end-tidal carbon dioxide (PET(CO(2))) increased in C (n = 16; 58.8 +/- 3.1 to 60.3 +/- 3.7 mm Hg; PMLE versus C: p < 0.001). PMLE increased respiratory frequency from 10.2 +/- 1.9 to 21.2 +/- 2.7 breaths/min (p < 0.0001). We conclude that PMLE during NREM increases V A possibly via activation of mechanoreceptor-afferent pathways rather than by respiratory entrainment. We speculate that such effect may provide future noninvasive ventilatory support strategies in patients with CCHS and mild phenotypic expression of their disease.

PDGF-beta receptor expression and ventilatory acclimatization to hypoxia in the rat.

Activation of platelet-derived growth factor-beta (PDGF-beta) receptors in the nucleus of the solitary tract (nTS) modulates the late phase of the acute hypoxic ventilatory response (HVR) in the rat. We hypothesized that temporal changes in PDGF-beta receptor expression could underlie the ventilatory acclimatization to hypoxia (VAH). Normoxic ventilation was examined in adult Sprague-Dawley rats chronically exposed to 10% O(2), and at 0, 1, 2, 7, and 14 days, Northern and Western blots of the dorsocaudal brain stem were performed for assessment of PDGF-beta receptor expression. Although no significant changes in PDGF-beta receptor mRNA occurred over time, marked attenuation of PDGF-beta receptor protein became apparent after day 7 of hypoxic exposure. Such changes were significantly correlated with concomitant increases in normoxic ventilation, i.e., with VAH (r: -0.56, P < 0.005). In addition, long-term administration of PDGF-BB in the nTS via osmotic pumps loaded with either PDGF-BB (n = 8) or vehicle (Veh; n = 8) showed that although no significant changes in the magnitude of acute HVR occurred in Veh over time, the typical attenuation of HVR by PDGF-BB decreased over time. Furthermore, PDGF-BB microinjections did not attenuate HVR in acclimatized rats at 7 and 14 days of hypoxia (n = 10). We conclude that decreased expression of PDGF-beta receptors in the dorsocaudal brain stem correlates with the magnitude of VAH. We speculate that the decreased expression of PDGF-beta receptors is mediated via internalization and degradation of the receptor rather than by transcriptional regulation.

N-Methyl-D-aspartate receptor expression in the nucleus tractus solitarii and maturation of hypoxic ventilatory response in the rat.

Ventilatory responses to hypoxia are critically dependent on the activation of N-methyl-D-aspartate (NMDA) glutamate receptors in adult rats. To investigate the role of NMDA receptors during development, we measured minute ventilation (V E) in 5-d, 10-d, and 15-d-old intact, freely behaving rat pups, using whole-body plethysmography during breathing of room air (RA), during hypoxia (10% O(2)), and during hypercapnia (5% CO(2)), both before and after administration of the NMDA receptor antagonist MK-801 (1 mg/kg intraperitoneally). MK-801 did not affect V E in RA in the younger animals, but increased both V E and respiratory frequency in the 15-d- old rats. Similarly, V E responses to hypoxia were unchanged from control values in young animals, whereas V E respones in 15-d-old rats showed significant attenuation under hypoxic conditions. In contrast, hypercapnic ventilatory responses were not altered by administration of MK-801 to rats at any age. To further examine the topographic distribution patterns of NMDA receptor-positive neurons in the caudal brainstem and their recruitment during hypoxia, we performed immunostaining for NMDA receptor subunit NR1 and c-fos after exposing rat pups at postnatal ages of 2 d, 5 d, 10 d, and 20 d and adult rats to either RA or 10% O(2) for 3 h. With advancing postnatal age, NR1 expression increased in the nucleus tractus solitarii (nTS), whereas it decreased in the hypoglossal nucleus. Hypoxic exposure was associated with increased c-fos expression in the nTS at all postnatal ages, with a marked increase occurring in >/= 10-d-old animals. Similarly, the density of c-fos-NR1 double-labeled neurons during hypoxia progressively increased with maturation. We conclude that NMDA glutamate receptor expression in the caudal brainstem undergoes postnatal maturation that closely parallels the development of the hypoxic ventilatory response in the rat.

Signaling pathways of the acute hypoxic ventilatory response in the nucleus tractus solitarius.

The nucleus tractus solitarii (nTS) provides the initial central synaptic relay to peripheral chemoreceptor afferent inputs elicited by changes in oxygen tension. Insofar, the overall cumulative evidence pointing towards the N-methyl-D-aspartate (NMDA) glutamate receptor as the critical receptor underlying the early component of the hypoxic ventilatory response (HVR) is reviewed in detail. In addition, we will present recent findings supporting a role for platelet-derived growth factor (PDGF) beta receptor activation in modulation of the late phase of HVR. This evidence underscores the proposal of a working model for intracellular signaling pathways, downstream to the NMDA glutamate and PDGF-beta receptors in nTS neurons, which may contribute to both the ventilatory characteristics of the acute hypoxic response and to subsequently occurring functional adaptations and synaptic plasticity phenomena.

AMPA glutamate receptors and respiratory control in the developing rat: anatomic and pharmacological aspects.

The developmental role of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) glutamate receptors in respiratory regulation remains undefined. To study this issue, minute ventilation (V(E)) was measured in 5-, 10-, and 15-day-old intact freely behaving rat pups using whole body plethysmography during room air (RA), hypercapnic (5% CO(2)), and hypoxic (10% O(2)) conditions, both before and after administration of the non-N-methyl-D-aspartate (NMDA) receptor antagonist 1,2,3, 4-tetrahydro-6-nitro-2,3-dioxobenzo[f]quinoxaline-7-sulfonamide disodium (NBQX; 10 mg/kg ip). In all age groups, V(E) during RA was unaffected by NBQX, despite reductions in breathing frequency (f) induced by increases in both inspiratory and expiratory duration. During hypoxia and hypercapnia, V(E) increases were similar in both NBQX and control conditions in all age groups. However, tidal volume was greater and f lower after NBQX. To determine if AMPA receptor-positive neurons are recruited during hypoxia, immunostaining for AMPA receptor (GluR2/3) and c-fos colabeling was performed in caudal brain stem sections after exposing rat pups at postnatal ages 2, 5, 10, and 20 days, and adult rats to room air or 10% O(2) for 3 h. GluR2/3 expression increased with postnatal age in the nucleus of the solitary tract (NTS) and hypoglossal nucleus, whereas a biphasic pattern emerged for the nucleus ambiguus (NA). c-fos expression was enhanced by hypoxia at all postnatal ages in the NTS and NA and also demonstrated a clear maturational pattern. However, colocalization of GluR2/3 and c-fos was not affected by hypoxia. We conclude that AMPA glutamate receptor expression in the caudal brain stem is developmentally regulated. Furthermore, the role of non-NMDA receptors in respiratory control of conscious neonatal rats appears to be limited to modest, albeit significant, regulation of breathing pattern.