Spontaneous crossed phrenic activity in the neonatal respiratory network.
Hemisection of the cervical spinal cord causes paralysis of the ipsilateral hemidiaphragm in adult rats. Activation of a latent crossed phrenic motor pathway can restore diaphragmatic function, although structural changes take place before the pathway can be activated. Since mechanisms are employed to eliminate non-functional projections during development, we predicted that this latent neural pathway might be active during development. Therefore, we examined the effect of spinal hemisection (C2) on respiratory-like activity bilaterally using the brainstem--spinal cord preparation from neonatal rats (0-4 days). Spontaneous crossed phrenic activity (respiratory-like activity recorded from the ipsilateral C4 or C5 ventral roots following C2 hemisection) was observed in an age-dependent manner; younger preparations exhibited more than older preparations. Increasing drive (increasing [K+] or superfusion of theophylline) either increased or induced crossed phrenic activity. Hemisection caused no change in the frequency, the burst area, duration or peak amplitude contralateral to hemisection. Unlike adult rats, this study shows that crossed phrenic activity is present in the in vitro respiratory network of neonatal rats suggesting that a crossed neural pathway may be functionally active in neonates.
Zimmer
M Beth
MB
Wayne State University, School of Medicine, Department of Anatomy and Cell Biology, 540 East Canfield, Detroit, MI 48201, USA. mzimmer@med.wayne.edu
Goshgarian
Harry G
HG
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D001993:Bronchodilator Agents / Q000494:pharmacology; D004525:Efferent Pathways / Q000166:cytology / Q000254:growth & development* / Q000293:injuries; D007839:Functional Laterality / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009415:Nerve Net / Q000166:cytology / Q000187:drug effects / Q000254:growth & development; D009473:Neuronal Plasticity / Q000502:physiology; D010791:Phrenic Nerve / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012125:Respiratory Center / Q000166:cytology / Q000187:drug effects / Q000254:growth & development*; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology; D012143:Respiratory Physiological Phenomena / Q000187:drug effects; D013116:Spinal Cord / Q000166:cytology / Q000254:growth & development*; D013119:Spinal Cord Injuries / Q000150:complications / Q000473:pathology / Q000503:physiopathology; D013806:Theophylline / Q000494:pharmacology
D001993:Bronchodilator Agents; D013806:Theophylline; D011188:Potassium