Hypoglossal and phrenic nerve responses to changes in oxygen tension during picrotoxin-induced seizures in the rat.
The aim of this study was to examine the response of phrenic and hypoglossal motor outputs to hyperoxia and 11% hypoxia during picrotoxin-induced seizures. Adult rats were anesthetized with a mixture of urethane with alpha-chloralose. The animals were bilaterally vagotomized, paralyzed, and artificially ventilated. Picrotoxin was administered intravenously in a cumulative dose until seizures occurred. The response to changes in oxygen tension was studied after the convulsive dose of picrotoxin and compared with the baseline level. The results show that the picrotoxin-induced seizures evoked a complex respiratory response that consisted of an augmentation of phrenic and hypoglossal nerve activities and irregular disturbances in phasic respiratory discharges. The excitation of the hypoglossal activity appeared earlier and showed a more irregular pattern than that of the phrenic activity. Hyperoxia elicited a similar decrease in neural respiratory outputs during the control and seizure conditions, suggesting the unaltered peripheral chemoreceptor mechanism. In the pre-seizure condition, hypoxia caused an initial excitation of the phrenic and hypoglossal outputs followed by some decline of the effect. During seizures, the striking effect of hypoxia was a decrease of the respiratory rate. A biphasic response to hypoxia was maintained in the hypoglossal activity due to stimulation of the hypoglossal amplitude. In contrast, in the phrenic activity the excitatory phase of hypoxia was absent and depression ensued. The mechanism underlying the facilitation of hypoxic respiratory depression during seizures is discussed.
Budzińska
K
K
Department of Respiratory Research, Medical Research Center, Polish Academy of Sciences, Warsaw, Poland. kbudzinska@cmdik.pan.pl
D000818:Animals; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004827:Epilepsy / Q000139:chemically induced* / Q000378:metabolism / Q000503:physiopathology*; D018496:Hyperoxia / Q000378:metabolism / Q000503:physiopathology; D007002:Hypoglossal Nerve / Q000187:drug effects* / Q000503:physiopathology; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010100:Oxygen / Q000008:administration & dosage / Q000378:metabolism*; D010791:Phrenic Nerve / Q000187:drug effects* / Q000503:physiopathology; D010852:Picrotoxin / Q000494:pharmacology*; D051381:Rats; D012119:Respiration / Q000187:drug effects
D010100:Oxygen; D010852:Picrotoxin