Superior laryngeal neurons directly excite cardiac vagal neurons within the nucleus ambiguus.
The aim of this study was to test whether superior laryngeal neurons have axon collaterals that synapse upon cardiac vagal neurons. Superior laryngeal neurons were tested as likely mediators of cardio-respiratory interaction because these neurons are active in post-inspiration, co-localized with cardiac vagal neurons, and have many axon collaterals within the nucleus ambiguus. Nontoxic fluorescent tracers were utilized to identify, in vitro, both superior laryngeal neurons that innervated the crico-thyroid muscle, and cardiac vagal neurons that projected to cardiac ganglia. Co-localization of these two populations of neurons demonstrated that cardiac vagal and superior laryngeal neurons are both co-localized in the nucleus ambiguus. Simultaneous dual patch clamp recordings were used to either inject depolarizing current and evoke an action potential (current clamp configuration) or control the voltage and depolarize an identified single superior laryngeal neuron (voltage clamp configuration) while simultaneously recording from a cardiac vagal neuron. Depolarization of some, but not all, individual superior laryngeal neurons elicited post-synaptic excitatory currents in cardiac vagal neurons, indicating that at least some superior laryngeal neurons monosynaptically synapse upon cardiac vagal neurons within the nucleus ambiguus.
Mendelowitz
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Department of Pharmacology, George Washington University, DC 20037, USA. dmendelowitz@hotmail.com
D000818:Animals; D000831:Animals, Newborn; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D006321:Heart / Q000502:physiology*; D007823:Laryngeal Nerves / Q000166:cytology* / Q000502:physiology*; D008526:Medulla Oblongata / Q000166:cytology* / Q000502:physiology*; D009434:Neural Pathways / Q000166:cytology* / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D051381:Rats