Non-nutritive swallowing (NNS) is especially important in the neonatal period for clearing secretions and gastro-pharyngeal reflux, and has been associated with neonatal apneas. One previous study has reported that systemic C-fiber blockade (CFB) inhibits induced swallowing in adult guinea pigs (Jin, Y et al, Am J Respir Crit Care Med. 1994). The aim of our present study was to investigate the effects of CFB on apnea and NNS frequency, and on the coordination between NNS and phases of the respiratory cycle in newborn lambs.
Eight CBF and 7 control lambs were chronically instrumented for recording electroencephalogram, eye movements, diaphragm and thyroarytenoid muscle activity, nasal airflow and electrocardiogram. CFB was induced by subcutaneous injection of capsaïcin (30mg/kg). All experiments were conducted in non-sedated lambs at 4 days of age, using a custom-made radiotelemetry system.
CFB lambs spent more time in active sleep than controls (15 ± 4% vs. 9 ± 3%, p = 0,03). Apnea frequency was not significantly different between CFB and control lambs, whatever the state of alertness (p between 0.2 and 0.8). NNS frequency was higher in CBF than control lambs (32 ± 8/h vs. 20 ± 10/h, p = 0.01) in QS. Finally, systemic C-fiber blockade had no effect on the coordination between NNS and phases of the respiratory cycle, whatever the state of alertness.
Our results suggest that C fibers inhibit NNS, but have no effect on the coordination between NNS and phases of the respiratory cycle in the neonatal period. Moreover, C fiber blockade has no effect on apnea frequency.
such studies may prove to be important in the use of capsaicin agonists or antagonists in the treatment of various conditions, including swallowing difficulties.
Charles Duvareille, None.