Respiratory and vasomotor responses to focal cooling of the ventral medullary surface (VMS) of the rat.
Experiments were performed on anesthetized, paralyzed and artificially ventilated rats after denervation of the vagus and carotid sinus nerves. The electrical activity of the phrenic and cervical sympathetic nerves (CS) along with the arterial blood pressure (BP) were monitored. Graded unilateral cooling of the ventral lateral surface (VMS) from 37 degrees C to 10 degrees C between 6th and 12th nerve rootlets did not affect the phrenic activity. Whereas, a significant depression or apnea was seen with cooling of an area between 1st cervical and 12th nerve rootlets. Bilateral cooling also produced similar respiratory responses. Respiratory depression could also be obtained during higher respiratory drive (7% CO2 in O2). On the other hand, a significant fall in BP and reduction in CS activity were observed with unilateral cooling in any of these VMS areas. However, the magnitude of BP decrease was less with 7% CO2 in O2 compared to 100% O2 breathing.
Mitra
J
J
Department of Medicine, University Hospitals of Cleveland, OH 44106.
Prabhakar
N R
NR
Overholt
J L
JL
Cherniack
N S
NS
D000818:Animals; D001794:Blood Pressure; D003080:Cold Temperature; D008526:Medulla Oblongata / Q000502:physiology*; D009407:Nerve Block; D010791:Phrenic Nerve / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012119:Respiration; D012121:Respiration, Artificial; D013564:Sympathetic Nervous System / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology*