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145 Can spinal respiratory rhythm generator control breathing movements during sleep in humans?: lessons from periodic limb movements (PLM)
Journées des Recherches Respiratoires
145 Can spinal respiratory rhythm generator control breathing movements during sleep in humans ? : lessons from periodic limb movements (PLM) 1
2
P. Haouzi , M. Younes 1 Laboratoire
de Physiologie, Faculté de médecine, Université H. Poincaré, Nancy, France 2 University of Toronto, Canada. [email protected]
Introduction : PLM are stereotyped sleep-related movements of the lower limbs. The current view is that a lack of inhibition of spinal locomotor centres by the dopaminergic descending pathway accounts for PLM, as supported by the effetcs of dopaminergic treatment, high incidence of PLM in Parkinson disease or in patients with spinal cord section. Methods : We studied the respiratory events associated with PLM in five consecutive patients. Respiratory flow, chest wall and abdominal movements were analysed breath-by-breath according to the occurrence of arousals based on EEG and chin EMG signals during PLM. The onset of respiratory flow changes was determined by comparing the respiratory flow and breathing movements of the breaths preceding and following the onset of contractions from an EMG signal. Results : We found that less than half of the limb movements (LM) trigger arousal episods which were associated with various ventilatory changes (increase in VT and f ). The majority of LM however does not produce any arousal and in many instances, respiratory changes clearly precede EMG activation in the form of a reduction in TE and a rise in VT. Conclusion : Such a time course is incompatible with 1- a ventilatory reflex activated from muscle afferents 2- an activation of ”respiratory” spino-reticular pathway secondary to stimulation of spinal locomotor centres. It is proposed that oscillations in respiration triggered at the onset of a series of PLM can eventually become autonomous with their own periodicity or efficient respiratory movements can be generated through mechanisms similar to, but independent of, those producing PLM. This implies that since PLM appears to be elaborated at the spinal level, spinal respiratory centers exist in adult humans and can produce breathing movements during sleep. Key-words: Control of breathing • Sleep.
146 Learned arousal response to hypoxia in newborn mice B. Bollen1, B. Matrot2, O. Van Den Bergh1, J. Gallego2 1
Catholic University of Leuven, Department of Psychology (Belgium) U676, Hôpital Robert-Debré, Paris, France 3 Faculté de Médecine d’Amiens, France. 2 INSERM
[email protected]
Introduction : In infants, the arousal response to hypoxia includes awakening, body movements and crying. Here, we examined the possibility that newborns learn to strengthen the defence response to hypoxia on the basis of past experience. We explored this possibility in 6-day old mice. To do this, we conducted a classical conditioning experiment in which newborn mice were exposed to artificial odours (lemon or peppermint, the conditioned stimuli, CS) while the fraction of inspired O2 (FIO2) was lowered to 10% (the unconditioned stimulus, US). We compared the production of USVs in response to odours previously paired with hypoxia (CS+) versus unpaired odours (CS-). Methods : Acquisition: 2-min normoxia, 2-min CS+/hypoxia, 2-min air and 2 min CS-/air. This sequence was repeated once (fig. 1 a).
Fig. 1.
Setup and results. Test: The pup was placed on the grid of the test apparatus (fig. 1 b). A cotton impregnated with odour (previously paired, CS+ or unpaired, CS-) was placed underneath the grid. We measured the total duration of USVs over 60 s. The dish was then removed and replaced by the dish containing the other odour (fig. 1 a-c) Results : The total duration of USVs was significantly longer when animals were exposed to the odour previously paired with hypoxia (CS+) than to the other odour (CS-, fig. 1 c, p = 0,0012). The conditioning effect occurred in both the CS+ lemon group and the CS+ peppermint group. Conclusion : The defence response to hypoxia may be broaden to previously neutral stimuli announcing hypoxia based on past experience. Thus, newborns may learn to anticipate hypoxia, and as a consequence, early defect of associative learning as those encountered in preterm newborns may disrupt the ability to learn adaptive behaviors against hypoxia. Key-words: Physiologie • Contrôle ventilatoire.
590
Rev Mal Respir 2006 ; 23 : 509-91
145 Can spinal respiratory rhythm generator control breathing movements during sleep in humans ? : lessons from periodic limb movements (PLM) 1
2
P. Haouzi , M. Younes 1 Laboratoire
de Physiologie, Faculté de médecine, Université H. Poincaré, Nancy, France 2 University of Toronto, Canada. [email protected]
Introduction : PLM are stereotyped sleep-related movements of the lower limbs. The current view is that a lack of inhibition of spinal locomotor centres by the dopaminergic descending pathway accounts for PLM, as supported by the effetcs of dopaminergic treatment, high incidence of PLM in Parkinson disease or in patients with spinal cord section. Methods : We studied the respiratory events associated with PLM in five consecutive patients. Respiratory flow, chest wall and abdominal movements were analysed breath-by-breath according to the occurrence of arousals based on EEG and chin EMG signals during PLM. The onset of respiratory flow changes was determined by comparing the respiratory flow and breathing movements of the breaths preceding and following the onset of contractions from an EMG signal. Results : We found that less than half of the limb movements (LM) trigger arousal episods which were associated with various ventilatory changes (increase in VT and f ). The majority of LM however does not produce any arousal and in many instances, respiratory changes clearly precede EMG activation in the form of a reduction in TE and a rise in VT. Conclusion : Such a time course is incompatible with 1- a ventilatory reflex activated from muscle afferents 2- an activation of ”respiratory” spino-reticular pathway secondary to stimulation of spinal locomotor centres. It is proposed that oscillations in respiration triggered at the onset of a series of PLM can eventually become autonomous with their own periodicity or efficient respiratory movements can be generated through mechanisms similar to, but independent of, those producing PLM. This implies that since PLM appears to be elaborated at the spinal level, spinal respiratory centers exist in adult humans and can produce breathing movements during sleep. Key-words: Control of breathing • Sleep.
146 Learned arousal response to hypoxia in newborn mice B. Bollen1, B. Matrot2, O. Van Den Bergh1, J. Gallego2 1
Catholic University of Leuven, Department of Psychology (Belgium) U676, Hôpital Robert-Debré, Paris, France 3 Faculté de Médecine d’Amiens, France. 2 INSERM
[email protected]
Introduction : In infants, the arousal response to hypoxia includes awakening, body movements and crying. Here, we examined the possibility that newborns learn to strengthen the defence response to hypoxia on the basis of past experience. We explored this possibility in 6-day old mice. To do this, we conducted a classical conditioning experiment in which newborn mice were exposed to artificial odours (lemon or peppermint, the conditioned stimuli, CS) while the fraction of inspired O2 (FIO2) was lowered to 10% (the unconditioned stimulus, US). We compared the production of USVs in response to odours previously paired with hypoxia (CS+) versus unpaired odours (CS-). Methods : Acquisition: 2-min normoxia, 2-min CS+/hypoxia, 2-min air and 2 min CS-/air. This sequence was repeated once (fig. 1 a).
Fig. 1.
Setup and results. Test: The pup was placed on the grid of the test apparatus (fig. 1 b). A cotton impregnated with odour (previously paired, CS+ or unpaired, CS-) was placed underneath the grid. We measured the total duration of USVs over 60 s. The dish was then removed and replaced by the dish containing the other odour (fig. 1 a-c) Results : The total duration of USVs was significantly longer when animals were exposed to the odour previously paired with hypoxia (CS+) than to the other odour (CS-, fig. 1 c, p = 0,0012). The conditioning effect occurred in both the CS+ lemon group and the CS+ peppermint group. Conclusion : The defence response to hypoxia may be broaden to previously neutral stimuli announcing hypoxia based on past experience. Thus, newborns may learn to anticipate hypoxia, and as a consequence, early defect of associative learning as those encountered in preterm newborns may disrupt the ability to learn adaptive behaviors against hypoxia. Key-words: Physiologie • Contrôle ventilatoire.
590
Rev Mal Respir 2006 ; 23 : 509-91