C-fiber blockade influence on non-nutritive swallowing in full-term lambs

Systemic C-fiber blockade (CFB) has been reported to inhibit induced swallowing in adult guinea pigs. The aim of this study was to investigate the effects of CFB on spontaneous, non-nutritive swallowing (NNS) frequency and NNS-respiration coordination in the neonatal period. Seven CFB lambs and seven control lambs aged 2 ± 1 days were chronically instrumented for recording electroencephalogram, eye movements, diaphragm EMG, thyroarytenoid muscle EMG, nasal airflow and electrocardiogram. Polysomnographic recordings were performed in non-sedated lambs, using radiotelemetry transmission. CFB lambs spent more time in active sleep than controls (p = 0.02). Frequency of non-nutritive swallowing was not different in CFB and control lambs, whatever the state of alertness. In addition, CFB did not disrupt the overall respiratory-swallowing coordination, inspiratory-related NNS being the most frequent and expiratory-related NNS the least in both CFB and control lambs. Further analyses revealed that CFB had no effect on baseline respiratory and heart rate, and apnea and sigh frequency, whatever the state of alertness. Our results suggest that, in the neonatal period, C-fibers are not involved in NNS frequency and have no influence on the overall respiratory-swallowing coordination.