Responses of feline medial medullary reticular formation neurons with projections to the C5-C6 ventral horn to vestibular stimulation

• Published in: Brain research Vol. 1018; no. 2; pp. 247 - 256
• Main Authors: WILKINSON, K. A, MAURER, A. P, SADACCA, B. F, YATES, B. J
• Format: Journal Article
• Language: English
• Published: London Elsevier 27.08.2004; Amsterdam; New York, NY
• Subjects: Analysis of Variance; Anatomy; Animals; Anterior Horn Cells - cytology; Anterior Horn Cells - physiology; Biological and medical sciences; Brain Mapping; Cats; Central nervous system; Diaphragm - innervation; Electric Stimulation; Fundamental and applied biological sciences. Psychology; Medulla Oblongata - cytology; Medulla Oblongata - physiology; Motor Neurons - physiology; Neural Pathways - cytology; Neural Pathways - physiology; Neurons - physiology; Posture; Reticular Formation - cytology; Reticular Formation - physiology; Rotation; Vertebrates: nervous system and sense organs; Vestibular Nerve - physiology; Vestibule, Labyrinth - innervation; Vestibule, Labyrinth - physiology; Fissipedia; Carnivora; Spinal cord; Central nervous system; Reticular formation; Projection; Phrenic motoneuron; Anterior spinal horn; Motor neuron; Inner ear; Vertebrata; Mammalia; Cat; Diaphragm; Vestibular system
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.05.080

Prior studies have shown that the vestibular system contributes to adjusting respiratory muscle activity during changes in posture, and have suggested that portions of the medial medullary reticular formation (MRF) participate in generating vestibulo-respiratory responses. However, there was previously no direct evidence to demonstrate that cells in the MRF relay vestibular signals monosynaptically to respiratory motoneurons. The present study tested the hypothesis that the firing of MRF neurons whose axons could be antidromically activated from the vicinity of diaphragm motoneurons was modulated by whole-body rotations in vertical planes that stimulated vestibular receptors, as well as by electrical current pulses delivered to the vestibular nerve. In total, 171 MRF neurons that projected to the C5-C6 ventral horn were studied; they had a conduction velocity of 34+/-15 (standard deviation) m/sec. Most (135/171 or 79%) of these MRF neurons lacked spontaneous firing. Of the subpopulation of units with spontaneous discharges, only 3 of 20 cells responded to vertical rotations up to 10 degrees in amplitude, whereas the activity of 8 of 14 neurons was affected by electrical stimulation of the vestibular nerve. These data support the hypothesis that the MRF participates in generating vestibulo-respiratory responses, but also suggest that some neurons in this region have other functions.