Effects of picrotoxin on apneustic respiration by tetrodotoxin in the rabbit.
The effects of carotid body chemoreceptor stimulation by NaCN and sustained lung inflation on TTX-induced apneustic respiration were studied before and after picrotoxin in the rabbit. Intravenous and intracarotid injections of TTX (30-100 micrograms) induced the apneusis. The characteristic phrenic responses induced by NaCN and lung inflation were not observed during the TTX-induced apneusis. The results indicate that apneustic respiration induced by TTX may cause a reduction of spontaneous cell activity in the medulla and pons respiratory neurons. In TXX-treated animals, picrotoxin partially restored the excitatory phrenic responses by NaCN, whereas the lung inflation effects were not restored. Therefore, it is most likely that the TTX-resistant brain stem respiratory neurons may be stimulated by picrotoxin and this effect also acts to elevate the sensitivity of inspiratory neurons closely related to the PC neurons.
D000818:Animals; D002344:Carotid Body / Q000378:metabolism; D002628:Chemoreceptor Cells / Q000187:drug effects; D003486:Cyanides / Q000494:pharmacology; D004558:Electric Stimulation; D000860:Hypoxia / Q000378:metabolism; D008168:Lung / Q000502:physiology; D010101:Oxygen Consumption / Q000187:drug effects*; D010791:Phrenic Nerve / Q000502:physiology; D010852:Picrotoxin / Q000494:pharmacology*; D011817:Rabbits; D012119:Respiration / Q000187:drug effects*; D013779:Tetrodotoxin / Q000494:pharmacology*; D014628:Vagotomy
D003486:Cyanides; D010852:Picrotoxin; D013779:Tetrodotoxin