Walter M St-John

..We conclude that the perfused juvenile rat preparation exhibits patterns of eupnea, apneusis and gasping which are similar to in vivo mammalian preparations...

..This discharge peaked at the onset of the gasp and then decremented during neural inspiration. We hypothesize that these 'pre-inspiratory' neuronal activities generate the gasp by intrinsic pacemaker mechanisms...

..However, gasping does depend upon a conductance through persistent sodium channels...

..125 microM) and methysergide (above 2.5 microM). We conclude that activation of adrenergic and 5-HT2 receptors is important to sustain gasping and to restore rhythmic respiratory activity after hypoxia-induced depression...

..These administrations did cause sedation. We conclude that conductance through persistent sodium channels plays little role in the neurogenesis of eupnea...

..Indeed, our results establish that hypoglossal discharge alone is an equivocal index of the pattern of overall ventilatory activity and that this is accentuated by hypercapnia and hypothermia...

..These changes characterize central apnea. The major conclusion is that seizures may result in recurrent periods of obstructive and central apnea. Thus, seizures can adversely alter respiratory function in a profound manner...

..Indeed, both pons and medulla appear essential for all aspects of eupnoea to be expressed...

..Results provide additional support for the conclusion that the in situ preparation demonstrates distinctly different patterns of automatic ventilatory activity, comparable to eupnea and gasping in vivo...

..The accuracy of this method of classification has not been established...

..This release is caused by cellular mechanisms that change the balance between membrane ionic currents. Moreover, these cellular mechanisms may be explicitly induced by alterations in the ionic and metabolic homeostasis...

..Results also provide additional support for our conclusion that activity of any single cranial nerve does not provide an accurate index of the type of respiratory rhythm, be it eupnea or gasping...

..We conclude that the neurogenesis of gasping is not dependent upon fast, chloride-mediated inhibitory synaptic transmission...

..These results add further support to the conclusion that the in situ preparation represents a model that accurately reproduces mechanisms of rhythm generation of both eupnea and gasping in vivo...

..These findings have significant negative implications for conclusions drawn from the in vitro medullary slice of mouse...

..Based upon the present and previous findings, we hypothesize that this burster discharge may be released when the brain is subject to severe hypoxia or ischaemia, and that this burster discharge could underlie gasping...

..These results support the concept that a loss of inhibitory glycinergic transmission is a critical factor in release of pacemaker mechanisms for gasping from the pontomedullary neuronal circuit for eupnea...

..Inhibition of serotonergic medullary raphé and extra-raphé neurons decreases ventilatory CO2 sensitivity and alters cardiovascular variables and sleep cycling, which may contribute to the sudden infant death syndrome...

..We conclude that OX(1)R in the rostral medullary raphe contribute to the hypercapnic chemoreflex in wakefulness, during the dark period in rats...

..Evidence from previous studies that support the validity of these criteria is presented herein. We conclude that pontile mechanisms play a critical role in the neurogenesis of eupnea...

..007). Within the first two postnatal weeks, the medullary 5-HT system plays an important role in cardiorespiratory control, mitigating spontaneous bradycardia, stabilizing the breathing pattern, and dampening the hypercapnic Ve response...

..In the Cool condition the ventilatory response to hypoxia is inhibited but appropriately so for the lower VO2 ...

..We conclude that CA neurones (1) promote wakefulness, (2) participate in central respiratory chemoreception, (3) stimulate breathing frequency, and (4) minimize breathing variability in REM sleep...

..We conclude that a region of the caudal mesencephalon or pons is necessary for the manifestation of depressions of ventilatory activity in the newborn pig...

..These findings do not rule out a role for gap junctions in the expression of eupnea or gasping, but they do demonstrate that these intermembrane channels are not obligatory for either rhythm to occur...

..These effects of caudal MR serotonergic neurons could be at a chemoreceptor site, e.g. the RTN, or at 'downstream' sites involved in rhythm and pattern generation...

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..to normal breathing? Are these rhythms similar to those of gasping, which is recruited when normal, eupnoeic breathing fails, or are these rhythms unique to the in vitro preparation and not related to any breathing pattern in vivo?..

..During eupnea, the activity patterns in the phrenic, hypoglossal and vagal nerves seem to originate from different sets of pre-motor neurons...

..We comment on the organization of this distributed central chemoreceptor system and suggest that interactions among sites are synergistic and not additive, which is an important aspect of its normal function...

..This genetic model allows examination of the role of excess 5-HT in ECF in the development of the control of breathing and central chemoreception, which may be pertinent to SIDS...

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..Disturbances of medullary raphé function can alter central chemoreception and normal sleep architecture, which may contribute to the pathogenesis of SIDS...

..We conclude that neurons with NK1R-ir somata or processes in the RTN/Ppy region are either chemosensitive or they modulate chemosensitivity. They also provide a tonic drive to breathe and may affect arousal...

..9 (0.7) Torr (N=5), which may inhibit other chemoreceptor sites. Multiple chemoreceptor sites may interact to provide high sensitivity in systemic hypercapnia and stability during heterogeneous stimulation and inhibition...

..Regional differences in pHi regulation between cortex and ventral medulla may be due to both chemosensitive and non-chemosensitive neurons...

..Other sources of input include the Kölliker-fuse nucleus, subceruleus, A5 region, and the paralemniscal zone...

..Central chemoreceptors in the NTS affect breathing in both sleep and wakefulness. The threshold for arousal in caudal NTS is greater than that for the stimulation of breathing...

..The results support our hypothesis that the orexin system participates importantly in central chemoreception in a vigilance-state- and diurnal-cycle-dependent manner and indicate a role for orexin in the important process of sighing...

..001; two-way ANOVA; P < 0.05, Tukey's post hoc test). We conclude that separate populations of serotonergic and adjacent NK1R-expressing neurones in the medulla are both involved in central chemoreception in vivo...

..NK1R-ir neurons in the ventral medulla are essential for normal central chemoreception, provide a drive to breathe, and modulate the peripheral chemoreceptor responses. These effects are not state dependent...

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..Chronic fluoxetine treatment in the medullary raphe increases the ventilatory response to hypercapnia in an unanesthetized rat model, an effect that may be due to facilitation of chemosensitive serotonergic neurons...

..We conclude that serotonergic activity in the MRR plays a role in the ventilatory response to hypercapnia, but not to hypoxia, and that MRR 5-HT1A receptors are also involved in thermoregulation and arousal...

..In addition, this approach should be useful to study unrestrained neonatal mice under conditions where body temperature approaches environmental temperature and barometric plethysmography cannot be used...

..They affect physiological control systems in many ways, perhaps not all measurable, via the study of the steady-state CO2 response...

..Conclusions: Central CA neurons have a net excitatory effect on breathing and chemoreception but a net inhibitory effect on blood pressure...

..We conclude that projections of orexin-containing neurons to the RTN contribute, via OX(1)Rs in the region, to the hypercapnic chemoreflex control during wakefulness and to a lesser extent, non-rapid eye movement sleep...

..We provide evidence for hypoxia-driven transformation within the central respiratory oscillator, in which gasping relies on persistent sodium current, whereas eupnea does not depend on this cellular mechanism...

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..These findings are discussed in the context of the role of endogenous bursting activity in the respiratory rhythm generation in vivo vs. in vitro and during normal breathing in vivo vs. gasping...

..In greatly reduced in vitro preparations, the importance of any individual neuromodulator, such as serotonin, may be exaggerated compared with its role in more intact preparations...

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..Results will provide a basis for understanding the failure of mechanisms for ventilatory neurogenesis, in apneas of neonates and adults. ..

..Such information might provide insights into dysfunctions of the control of ventilation in humans, such as in "sleep apneas" or the "sudden infant death syndrome." ..

..Such information might provide insights into dysfunctions of the control of ventilation in humans, such as in "sleep apnea" or the "sudden infant death syndrome." ..

..We believe that results of studies proposed herein will provide significant insights into the mechanisms responsible for the neurogenesis of automatic ventilatory activity...