Firing properties of identified superior laryngeal neurons in the nucleus ambiguus in the rat

Superior laryngeal motoneurons control muscles in the larynx and recent wor k has shown they also have axon collaterals that project to cardiac vagal n eurons in the nucleus ambiguus. The present study was undertaken to identif y and examine the firing properties of superior laryngeal neurons (SLNs) in the rat. SLNs typically fired spontaneously and repetitively at a rate of 4-7 Hz. The firing was continuous and showed little bursting activity. Firi ng evoked afterhyperpolarizations were insensitive to apamin but blocked by charybdotoxin. The voltage-gated currents in SLNs consist of a TTX-sensiti ve Na current and a 4-aminopyridine sensitive K current. It is likely I:hat the activity of these neurons not only control respiratory laryngeal muscl es, but may also provide an interaction between the respiratory system and the control of the heart rate. (C) 2001 Elsevier Science Ireland Ltd. All r ights reserved.