Convergent carotid sinus nerve and superior laryngeal nerve afferent inputs to neurons in the NTS

A population of 43 neurons in the nucleus of the solitary tract (NTS) was identified in pentobarbital sodium anesthetized, paralyzed, and artificially ventilated cats that received convergent inputs from carotid sinus nerve (CSN) and superior laryngeal nerve (SLN) afferents. In 21 neurons, electrical stimulation of the CSN and SLN each evoked an excitatory postsynaptic potential (EPSP; mean onset latency ± SE of CSN-evoked input = 7.2 ± 0.8 ms, range 2.1-14.1 ms; of SLN-evoked input = 10.3 ± 2.1 ms, range 2.8-46.8 ms). In 22 neurons, electrical stimulation of either the CSN or SLN evoked an EPSP/inhibitory postsynaptic potential (IPSP) sequence (CSN-evoked input - 6.7 ± 0.6 ms, range 2.1-12.2 ms; SLN-evoked input - 8.4 ± 0.8 ms, range 3.0-19.4 ms). Spatial interactions (facilitation, summation, occlusion) and time-dependent inhibitory interactions were observed between the convergent inputs. Natural stimulation of specific receptors indicated that 14 cells received a convergent excitatory input from carotid sinus baroreceptors and laryngeal mechanoreceptors, 10 received a convergent excitatory input from carotid body chemoreceptors and laryngeal mechanoreceptors, and 5 received a convergent excitatory input from baroreceptors, chemoreceptors, and laryngeal mechanoreceptors. The interactions and various patterns of convergence suggest a significant integration of convergent inputs from disparate afferent sources by these neurons.