Pulmonary C-fibers elicit both apneusis and tachypnea in the rabbit.
The effects of phenylbiguanide (PBG) on phrenic nerve and pulmonary C-fibers were studied in anesthetized spontaneously breathing rabbits with unilateral vagotomy. Right atrial injections of PBG at low (10 micrograms/kg) and high (100 micrograms/kg) dose resulted in a shallow tachypnea and apneusis followed by tachypnea, respectively, and these effects were blocked by procaine treatment of the vagus nerve. Also, the injection of PBG (100 micrograms/kg) still evoked the rapid shallow breathing preceded by apneusis in carotid chemoreceptor-denervated animals. Vigorous stimulation of pulmonary C-fibers by PBG (100 micrograms/kg) coincided with apneusis and the response was followed by a more modest increase in activity associated with tachypnea. Administration of PBG (10 micrograms/kg) into the right atrium caused an increase in pulmonary C-fiber activity associated with tachypnea. However, a small dose of PBG injected into the aortic circulation had no effect on the C-fiber activity but did inhibit respiration. These results suggest that the stimulation of pulmonary C-fibers via PBG injection can produce both inspiratory apnea and tachypnea.
Matsumoto
S
S
Department of Physiology, Fukushima Medical College, Japan.
Kanno
T
T
Yamasaki
M
M
Nagayama
T
T
Shimizu
T
T
D000287:Administration, Topical; D000818:Animals; D001645:Biguanides / Q000494:pharmacology; D001980:Bronchi / Q000098:blood supply; D005260:Female; D006325:Heart Atria; D007267:Injections; D008168:Lung / Q000294:innervation*; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology*; D011343:Procaine / Q000494:pharmacology; D011652:Pulmonary Circulation; D011817:Rabbits; D012120:Respiration Disorders / Q000209:etiology*; D014630:Vagus Nerve
D001645:Biguanides; D011343:Procaine; C008846:phenyl biguanide