Acute intermittent hypoxia (AIH) elicits a form of respiratory plasticity known as long-term facilitation (LTF). Here, we tested four hypotheses in unanesthetized, spontaneously breathing rats using radiotelemetry for EEG and diaphragm electromyography (Dia EMG) activity: 1) AIH induces LTF in Dia EMG activity; 2) diaphragm LTF (Dia LTF) is more robust during sleep vs. wakefulness; 3) AIH (or r...

Age and the estrus cycle affect time-dependent respiratory responses to episodic hypoxia in female rats. Respiratory long-term facilitation (LTF) is enhanced in middle-aged vs. young female rats (72). We tested the hypothesis that phrenic and hypoglossal (XII) LTF are diminished in acyclic geriatric rats when fluctuating sex hormone levels no longer establish conditions that enhance LTF. Chroni...

Long-term facilitation (LTF) of breathing elicited by episodic hypoxia (EH) is an extensively studied example of plasticity of respiratory motor behavior. Previous studies employed the paradigm of EH wherein each episode of hypoxia was 5 min. This paradigm is rarely encountered in nature. Brief episodes of hypoxia are encountered frequently with recurrent apneas, wherein hypoxic episodes last a...

BACKGROUND Increasingly, patients receiving methadone treatment are found in low threshold facilities (LTF), which provide needle exchange programmes in Switzerland. This paper identifies the characteristics of LTF attendees receiving methadone treatment (MT) compared with other LTF attendees (non-MT). METHODS A national cross-sectional survey was conducted in 2006 over five consecutive days ...

Respiratory long-term facilitation (LTF) is a long-lasting (>1 h) augmentation of respiratory motor output that occurs even after cessation of hypoxic stimuli, is serotonin-dependent, and is thought to prevent sleep-disordered breathing such as sleep apnea. Raphe nuclei, which modulate several physiological functions through serotonin, receive dense projections from orexin-containing neurons in...

The respiratory system is attentive, adaptive, learns and has memory. The respiratory system remembers repeated respiratory challenges to fine tune its motor activity by modulating neuronal synaptic strength. This phenomenon, respiratory long term facilitation (LTF), functions to strengthen the ability of respiratory motor neurons to enhance contraction of breathing muscles. LTF could serve as ...

Respiratory long-term facilitation (LTF), a serotonin-dependent, persistent augmentation of respiratory activity after episodic hypoxia, is enhanced by pretreatment of chronic intermittent hypoxia (CIH; 5 min 11-12% O2-5 min air, 12 h/night for 7 nights). The present study examined the effects of methysergide (serotonin 5-HT1,2,5,6,7 receptor antagonist), ketanserin (5-HT2 antagonist), or cloza...

The respiratory control system is not just reflexive, it is smart, it learns, and, in fact, it has a memory. The respiratory system listens to and carefully remembers how previous stimuli affect breathing. Respiratory memory is laid down by adjusting synaptic strength between respiratory neurons. For example, repeated hypoxic bouts trigger a form of respiratory memory that functions to strength...

Long-term facilitation (LTF) of synaptic transmission was investigated in the crayfish opener muscle to determine the factors necessary for its induction and expression. LTF was induced without action potentials by intracellular depolarization of presynaptic nerve terminals. Following induction, the synaptic transmission was enhanced by about 80% for a period of several hours. Intracellular rec...

Episodic hypoxia induces a persistent augmentation of respiratory activity, termed long-term facilitation (LTF). Phrenic LTF saturates in anesthetized animals such that additional episodes of stimulation cause no further increase in LTF magnitude. The present study tested the hypothesis that 1) ventilatory LTF also saturates in awake rats and 2) more severe hypoxia and hypoxic episodes increase...