Carotid chemoafferent plasticity in adult rats following developmental hyperoxia.
Developmental hyperoxia impairs carotid chemoreceptor development and induces long-lasting reduction in carotid sinus nerve (CSN) responses to hypoxia in adult rats. Studies were carried out to determine if CSN responses to acute hypoxia would exhibit hypoxia-induced plasticity in adult 3-5-months-old rats previously treated with postnatal hyperoxia (60% O2, PNH) of 1, 2, or 4 weeks duration. CSN responses to acute hypoxia were assessed in adult rats exposed to 1 week of sustained hypoxia (12% O2, SH). In normal adult rats and adult rats treated with 1 week of PNH, CSN responses to acute hypoxia were significantly increased in urethane-anesthetized rats when studied 3-5 h after SH. Apparent increases in CSN responses to hypoxia were not significant in rats treated with 2 weeks of PNH and were clearly absent after 4 weeks of PNH, but exponential analysis suggests a PNH duration-dependent plasticity of the CSN response to acute hypoxia after SH. In a second study rats exposed to 2 weeks of PNH were treated with SH for 1 week as adults and acute hypoxic responses were tested 4-5 months later. CSN responses in these rats were unaffected by SH suggesting a lack of persistent SH-induced functional plasticity. We conclude that rats treated with 1 week of PNH retain the capacity for hypoxia-induced plasticity of carotid chemoafferent function and some potential for plasticity may be present after 2 weeks of PNH, whereas 4 weeks of PNH impairs the capability of rats to exhibit plasticity following 1 week of SH.
Bisgard
Gerald E
GE
Department of Comparative Biosciences, University of Wisconsin, School of Veterinary Medicine, 2015 Linden Drive, Madison, WI 53706, USA. bisgardg@svm.vetmed.wisc.edu
Olson
E Burt
EB
Bavis
Ryan W
RW
Wenninger
Julie
J
Nordheim
Erik V
EV
Mitchell
Gordon S
GS
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002344:Carotid Body / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D005260:Female; D018496:Hyperoxia / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology*; D010791:Phrenic Nerve / Q000254:growth & development / Q000503:physiopathology; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors