TY - JOUR
T1 - Chronic hypoxia abolishes expiratory prolongation following carotid sinus nerve stimulation in the anesthetized rat
AU - Ilyinsky, Oleg
AU - Mifflin, Steve
N1 - Funding Information:
The authors gratefully acknowledge the technical assistance of O. Tolstykh. This work was supported by HL-41894.
PY - 2005/4/15
Y1 - 2005/4/15
N2 - In anesthetized rats, increases in phrenic nerve (PN) amplitude and frequency during brief periods of hypoxia or electrical stimulation of the carotid sinus nerve (CSN) are followed by an increase in expiratory duration. We investigated the effects of chronic exposure to hypoxia on PN responses to CSN stimulation. In Inactin anesthetized (100 mg/kg) Sprague-Dawley rats PN discharge and arterial pressure responses to 10-120 s of CSN stimulation (20 Hz, 0.2 ms duration pulses) were recorded after 7-10 days exposure to hypoxia (10 ±. 5% O2). In normoxic rats, the degree of CSN-evoked expiratory prolongation was dependent upon the duration of CSN stimulation. CSN-evoked increases in PN burst amplitude were not different comparing chronic hypoxic rats to rats maintained at normoxia while CSN-evoked increases in PN burst frequency were greater in chronic hypoxic rats (p <. 05). CSN-evoked expiratory prolongation was abolished in chronic hypoxic rats. Following chronic hypoxia, changes occur within the central processing of arterial chemoreceptor inputs so that CSN stimulation evokes an enhanced PN frequency response and no expiratory prolongation.
AB - In anesthetized rats, increases in phrenic nerve (PN) amplitude and frequency during brief periods of hypoxia or electrical stimulation of the carotid sinus nerve (CSN) are followed by an increase in expiratory duration. We investigated the effects of chronic exposure to hypoxia on PN responses to CSN stimulation. In Inactin anesthetized (100 mg/kg) Sprague-Dawley rats PN discharge and arterial pressure responses to 10-120 s of CSN stimulation (20 Hz, 0.2 ms duration pulses) were recorded after 7-10 days exposure to hypoxia (10 ±. 5% O2). In normoxic rats, the degree of CSN-evoked expiratory prolongation was dependent upon the duration of CSN stimulation. CSN-evoked increases in PN burst amplitude were not different comparing chronic hypoxic rats to rats maintained at normoxia while CSN-evoked increases in PN burst frequency were greater in chronic hypoxic rats (p <. 05). CSN-evoked expiratory prolongation was abolished in chronic hypoxic rats. Following chronic hypoxia, changes occur within the central processing of arterial chemoreceptor inputs so that CSN stimulation evokes an enhanced PN frequency response and no expiratory prolongation.
KW - Carotid nerve stimulation
KW - Chronic hypoxia
KW - Expiratory prolongation
KW - Phrenic nerve
KW - Post-hypoxic frequency decline
KW - Rat
UR - http://www.scopus.com/inward/record.url?scp=14844293566&partnerID=8YFLogxK
U2 - 10.1016/j.resp.2004.12.005
DO - 10.1016/j.resp.2004.12.005
M3 - Article
C2 - 15766915
AN - SCOPUS:14844293566
SN - 1569-9048
VL - 146
SP - 269
EP - 277
JO - Respiratory Physiology and Neurobiology
JF - Respiratory Physiology and Neurobiology
IS - 2-3
ER -