Effect of hypothermia on respiratory rhythm generation in hamster brainstem–spinal cord preparations

• Published in: Respiratory physiology & neurobiology 2004-09, Vol.142 (2), p.237-249
• Main Authors: Zimmer, M.Beth, Milsom, W.K.
• Format: Article
• Language: English
• Subjects: Action Potentials - physiology; Analysis of Variance; Animals; Animals, Newborn; Biological and medical sciences; Brain Stem - cytology; Brain Stem - physiology; Cardiorespiratory control. Arterial mecano- and chemoreceptor; Cold Temperature; Cricetinae; Denervation; Female; Fundamental and applied biological sciences. Psychology; Hypothermia; Hypothermia - physiopathology; In Vitro Techniques; Male; Mammals; Mesocricetus; Neurons - physiology; Pattern of breathing; Pregnancy; Respiration; Respiratory pattern generation; Respiratory rhythm generation; Spinal Cord - cytology; Spinal Cord - physiology; Spinal Nerve Roots - physiology; Syrian hamster; Temperature; Vertebrates: respiratory system
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2004.06.005

This study examined the effect of hypothermia on respiratory neural output from brainstem–spinal cord preparations of a cold tolerant rodent, the Syrian hamster. Brainstem–spinal cords from neonatal hamsters (0–6 days) were placed in a recording dish and respiratory-like neural activity was recorded from roots of the first cervical nerve. The preparations were cooled and warmed in a continuous or stepwise fashion. Inputs from the pons completely inhibited neural activity under steady state conditions. With the pons removed, fictive breathing was robust. Cooling caused respiratory arrest, followed by spontaneous resumption of activity on re-warming. Preparations from older hamsters (4–6 days old) were more cold tolerant than younger preparations (0–3 days old). Motor discharge was episodic during continuous cooling, and seizure-like discharge was observed during continuous warming. These phenomena were not observed with stepwise temperature changes suggesting that transient temperature effects on membrane properties may be involved. These preparations were not as cold tolerant as hamster pups in vivo but they retained the ability to autoresuscitate at all ages studied.