Developmental changes in the spatio-temporal pattern of respiratory neuron activity in the medulla of late fetal rat.
We investigated how the spatio-temporal pattern of respiratory neuron network activity in the ventral medulla changes during the late fetal period of rat. Brainstem-spinal cord preparations isolated from rat fetuses on embryonic days 17-21 (E17-E21) were stained with a voltage-sensitive dye for optical image analysis of neuronal activity of the ventral medulla. The spatio-temporal pattern of respiratory neuron activity in the preparation from E20 to E21 was basically identical to that of neonatal rat; pre-inspiratory activity in a limited region of the rostral ventrolateral medulla, the para-facial region, preceded by several hundred milliseconds the onset of inspiratory activity in the more caudal ventrolateral medulla, the pre-Bötzinger complex level. In contrast, in E17-E18 specimens, pre-inspiratory activity could not be detected in the rostral medulla at the level of the facial nucleus. Neuronal activity appeared to begin at the pre-Bötzinger complex level shortly before onset of the inspiratory burst. Strong activity then developed in the facial nucleus and peaked in the post-inspiratory phase. The transition of these patterns of respiratory activity occurred at E19. We conclude that the changes in the spatio-temporal pattern of neuronal activity reflect developmental changes in the cellular elements underlying rhythm generation in the fetal respiratory neuron network. We suggest that the pre-inspiratory neuron network of the para-facial region in the rostral ventrolateral medulla functions as the rhythm generator after E19/20.
Onimaru
H
H
Department of Physiology, Showa University School of Medicine, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan. oni@med.showa-u.ac.jp
Homma
I
I
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D004594:Electrophysiology; D005260:Female; D007091:Image Processing, Computer-Assisted; D008526:Medulla Oblongata / Q000196:embryology / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D009046:Motor Neurons / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D012137:Respiratory System / Q000294:innervation*