Reflex Responses to Chemoreceptor Stimulation

In cats anesthetized with chloralose-urethane, the central respiratory chemoreceptors were exposed to mock CSF of pH 7.02, 7.20, or 7.57. The right carotid body was simultaneously stimulated by intracarotid injections of 40, 80, or 160 μg sodium cyanide in 200 μl Ringer solution. The left carotid nerve and, in some animals, both vagosympathetic truncs were dissected. It could be demonstrated the the increase in ventilation produced by application of NaCN to the peripheral chemoreceptors is significantly larger at high than at low mock CSF pH (i.e. at low than at high central stimulus intensity). In vagotomized cats the responses of VT and gelai to NaCN similarly depend upon CSF pH; they are somewhat larger, though, than in intact animals. These results are discussed as compared with results reported by different authors.

Interaction of peripheral and central respiratory drives in cats. I. Effects of sodium cyanide as a peripheral chemoreceptor stimulus at different levels of CSF pH.

An 9 Hunden fuhrten wir Kurz- und Langzeit-Histamininhalationen durch. Eine masige Obstruktion der Atemwege mit Verteilungsstorungen durch Spasmen im Bereich der Bronchiolen last sich mit Konzentrationen erreichen, welche noch kreislaufinaktiv bleiben. Bei langerdauernder Histamininhalation lassen diese Wirkungen auf die Bronchomotorik und den Kreislauf nach. Antihistaminica heben den Effekt des inhalierten Histamins an Bronchien und am Kreislauf weitgehend auf.

Der Einflu\ biogener Amine auf die Atmung und den kleinen Kreislauf

In anesthetized rabbits rebreathing oxygen the respiratory and circulatory responses to increased
 
$$P_{A_{{\text{CO}}_{\text{2}} } } $$

 were determined repeatedly in the same animal before and after inactivation of the vagus nerves by cold blocking and finally sectioning. In some animals responses were also obtained by blocking the vagi during respiration of constant mixtures of CO2 and O2. With intact vagi the
 
$$\dot V/P_{A_{{\text{CO}}_{\text{2}} } } $$

 response curve was, on the average, practically linear up to an increase of the
 
$$P_{A_{{\text{CO}}_{\text{2}} } } $$

 by 27 Torr. Inactivation of the vagi caused a small increase of the resting ventilatory minute volume during the initial breathing of pure oxygen, and a corresponding decrease of the resting
 
$$P_{A_{{\text{CO}}_{\text{2}} } } $$

 . In the range of small increases of
 
$$P_{A_{{\text{CO}}_{\text{2}} } } $$

 the
 
$$\dot V/P_{A_{{\text{CO}}_{\text{2}} } } $$

 response curve was significantly steepened and shifted to higher ventilatory values by the inactivation. With greater increases, the slope of the response with inactivated vagi was flatter and shifted to lower ventilatory values as compared with intact vagi. These effects were the result of corresponding changes of the response curves for tidal volume and respiratory rate: Inactivation considerably steepened the
 
$$\dot V_T /P_{A_{{\text{CO}}_{\text{2}} } } $$

 response at low values of
 
$$\Delta P_{A_{{\text{CO}}_{\text{2}} } } $$

 while flattening the response at high values, whereas the
 
$$f/P_{A_{{\text{CO}}_{\text{2}} } } $$

 curve was only depressed at all stages of hypercapnia. The results were principally the same whether the carotid sinus nerves were intact or sectioned. Vagal inactivation had only little influence on the reactions of systemic blood pressure and heart rate to the increase of
 
$$P_{A_{{\text{CO}}_{\text{2}} } } $$

 . It is concluded that vagal reflexes, possibly from stretch receptors of the lungs, modify the ventilatory efficacy of the central chemosensitive drive of respiration in the rabbit.

The roll of the vagus nerves in the respiratory response to CO 2 under hyperoxic conditions.

In rabbits rebreathing oxygen one carotid sinus nerve was stimulated repeatedly by electrical stimuli of constant intensity, both before and after inactivation of vagi by cold blocking or sectioning. In animals with intact vagi the reflex hyperpnea elicited by the nerve stimulation decreased only slightly with increasing hypercapnia. After inactivation of the vagi the stimulatory effect was, at normalPACO2, mostly greater than in the intact condition. But with increasing hypercapnia the decrease of the reflex hyperpnea was generally steeper than in the intact preparation, sometimes reaching even lower values than before inactivation. The depressant effects of the stimulation on systemic blood pressure and heart rate were not distinctly changed by the increase ofPACO2, neither with intact nor with inactivated vagi. It is concluded that the ventilatory effect of chemoreceptor afferents is modified both by centralPCO2 and by vagal afferents.

Der Einflu desP A CO 2 auf die Wirkung der Sinusnervenreizung bei intakten und ausgeschalteten Nn. vagi@@@The influence ofP A CO 2 on the effects of sinus nerve stimulation with intact and inactivated vagi

Vor bald vier Jahrzehnten haben J.F. und C. Hegmans die arte~iellen Chemorezeptoren ,des Glomus caroticum und aorticttm entdeekt. Eine intensive Forschung hat s:ei.ther der Frage gego]ten, ob es in der K6rperperipherie noeh andere ehemos.ensible Zanen im Dienste der Atmungsregttlatian gibt. Z.ahlreiehe reflektorisehe Atmungssteigerungen wurden beschrieben, die meist naeh Injektian groBer Dosen Cyanid, S~iuren und diverser pharmakologiseher Substanzen in Organarterien beobachtet wurden. Keine dieser Wirkungen kat bis jetzt die Kriterien einer spezifisehen Sensibfli.t/it ffir Sauerstoffmangel bzw. CO2 und H-Ionen erffillen k6nnen. Ffir alle gilt der Einwand, .dab hohe Konzer~trationen van Chemorezeptorenreizstoffen unspezJfiseh aneh andere Rezeptoren erregen ~nd fiber diese zu Atmungswirkungen ffihren kSnnen. In jiiangster Zeit wird vor allem die Existenz ehemosensibler Strukturen im Bereieh der P,tdmonalarterien 11 und der vom Aortenbogen abzweigenden Arterienst~imme a ,diskutiert. Die Abgrenztmg der Chemoreflexe aus dem Versorgungsgebiet des Lungen-o,der Herz~agus ist noeh in maneher Hinsieht problematiseh. Denn das Glomus ,aorti,eum, dessen Afferenzen tells fiber den Depressor, tefls fiber .den Vagus laufen, ist w.egen seiner Unzul~ngli,ehke~t wenig erforseht. MSglieherweise geben manehe dem Glomt~s zugesehriebenen Atmungswirkungen, besonders pharmakelogis.ehe, van anderen Stmkturen dieses Innervafior~sgebietes aus. Unter diesem Vorbehalt sind jedoeh die vom Vagus und Sinusnerven vermittelten Chemo,afferenzen bisher die einzigen geblieben, ,die normalerweise ffi_r die Chemoregulation der Atmung van Bedeuttmg sind. Die eigentliehen Meehanismen der Erregungsbildung ~nd Fortleitung im Glomus sind noeh ungekl~irt 2s, 36. Versekiedene Theorien, die einen spezifis,ehen Reizoder humoralen t2bertr~igerstoff annehmen, baben keine allgemeine Anerkennung gefunden. Iseh~imie 52,

P. Kiwull

Papers

Die Interferenz zentraler und peripherer Mechanismen bei der chemischen Steuerung der Atmung