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Developmental Respiratory and Endocrinology Laboratories, Department of Pediatrics, McGill University, and The Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada H3H 1P3
Received 16 September 1996; accepted in final form 23 April 1997.
Waters, Karen A., André Laferrière, Julie
Paquette, Cynthia Goodyer, and Immanuela R. Moss. Curtailed
respiration by repeated vs. isolated hypoxia in maturing piglets is
unrelated to NTS ME or SP levels. J. Appl.
Physiol. 83(2): 522-529, 1997.
In early
development, respiratory disorders can produce recurring hypoxic
episodes during sleep. To examine possible effects of daily repeated
vs. isolated hypoxic hypoxia, cardiorespiratory functions and central,
respiratory-related neuromodulator levels in 21- to 32-day-old,
chronically instrumented, unsedated piglets were compared between a
fifth sequential daily hypoxia and an isolated hypoxia (10%
O2-90%
N2 for 30 min). Diaphragmatic
electromyographic activity, heart rate and arterial pressure, and pH
and gas tensions were measured. In vivo microdialysis, via chronically
implanted guides, served to sample interstitial substance P (SP) and
methionine-enkephalin (ME) at the level of the respiratory-related
nucleus tractus solitarii (NTS). Compared with an isolated hypoxia,
repeated hypoxia resulted in 1)
lower respiratory frequency (f), ventilation equivalent, and arterial
pH, higher arterial PO2
during hypoxia, and lower f in recovery from hypoxia; and
2) increased SP concentrations but
no change in ME concentrations. We conclude that, in these maturing
swine, repeated vs. isolated hypoxic exposure curtails respiratory
responses to hypoxia by a mechanism(s) unrelated to SP or ME levels at
the NTS.
development; diaphragmatic electromyogram; in vivo microdialysis; methionine-enkephalin; substance P ; nucleus tractus solitarii
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