1. After spinal transection at the medulla-spinal junction the thoracic respiratory movements no longer appear in the adult animals, nevertheless the sporadic spike discharges can be recorded from the intercostal muscles. 2. Both in the acute and chronic experiments the spinal cord is transected at the two levels of Th7 and Thl1 respectively and all the dorsal rootlets coming into that part of the cord lying between the transections are severed. The sporadic spike discharges with irregular intervals varying about 0.5 to 3.0 sec. can be recorded from intercostal muscles in the 8th to 10th segments of the spinal cord isolated. There can never be found any reflex influence of the skin stimulation upon the discharges, which also disappear provided the intercostal nerves innervating the muscles are severed. 3. From these results it may be concluded that the spinal cord is endowed
with an ability to initiate the impulses autochthonously to excite the intercostal muscles, even though it is only poorly developed in the adult animals.</p

Hukuhara, Takesi

kotani, Satoru

Sumi, Tadaaki

Okayama University Scientific Achievement Repository

Acta Medica OkayamaVolume 14, Issue 4 1960 Article 6DECEMBER 1960Automatic activies of the spinal cordconcerned with the respiratory movementsTakesi Hukuhara∗ Tadaaki Sumi†Satoru kotani‡∗Okayama University,†Okayama University,‡Okayama University,Copyright c©1999 OKAYAMA UNIVERSITY MEDICAL SCHOOL. All rights reserved.Automatic activies of the spinal cordconcerned with the respiratory movements∗Takesi Hukuhara, Tadaaki Sumi, and Satoru kotaniAbstract1. After spinal transection at the medulla-spinal junction the thoracic respiratory movementsno longer appear in the adult animals, nevertheless the sporadic spike discharges can be recordedfrom the intercostal muscles. 2. Both in the acute and chronic experiments the spinal cord istransected at the two levels of Th7 and Thl1 respectively and all the dorsal rootlets coming intothat part of the cord lying between the transections are severed. The sporadic spike dischargeswith irregular intervals varying about 0.5 to 3.0 sec. can be recorded from intercostal muscles inthe 8th to 10th segments of the spinal cord isolated. There can never be found any reflex influenceof the skin stimulation upon the discharges, which also disappear provided the intercostal nervesinnervating the muscles are severed. 3. From these results it may be concluded that the spinalcord is endowed with an ability to initiate the impulses autochthonously to excite the intercostalmuscles, even though it is only poorly developed in the adult animals.∗Copyright c©OKAYAMA UNIVERSITY MEDICAL SCHOOLActa Med. Okayama 14, 271-277 (1960)AUTOMATIC ACTIVITIES OF THE SPINAL CORD CONCERNEDWITH THE RESPIRATORY MOVEMENTSTakesi HUKUHARA, Tadaaki SUMI and Satoru KOTANIDepartment of Physiology, Okayama University Medical School, OkayamaReceived for publication, Oct. 27, 1960It is a question of a long standing whether or not there exists in the spinalcord a center, where the respiratory impulses can be originated spontaneously.The results obtained up to the present time by some investigators (ROKITANSKY\SCHROFF6, LANGENDORFF2 and MARCKWALD3) show that the respiratory move-ments of the thorax in infant or newborn animals still persist even after thespinal cord is transected at medullo-spinal junction, however, such a persistentrespiration can not be observed in adult animals.Recently KOTANIl reported the presence of some sporadic spike dischargesin the intercostal muscles even in spinalized adult animals, although no recog-nizable contraction seems to take place. This, however, can not be at once beconstrued as sporadic spikes to originate autochthonously in the spinal cord itself,since these are likely to be provoked reflexively by stimuli of peripheral sources(i. e., skin, muscle, joint and so on). The following results may offer a clue toa better understanding of the point at issue.METHODSAs experimental animals newborn and adult dogs, cats and rabbits areused. Each newborn animal, less than 2 days old, is decapitated without anyanesthetics and the change of respiratory movements both in the thorax and inthe nostrils or larynx are observed or recorded on the smoked surface of thedrum of a kymograph by clipping the skin of the regions concerned.In adult cats and dogs the spinal cord is on the one hand exposed by lami-nectomy under local anesthesia with 1 % solution of xylocaine. In one series ofexperiments the cord is then transected at the medulla-spinal junction. In anotherseries of experiments the spinal cord is at first transected at the level betweenTh6 and Th7 rostrally as well as between ThlO and Thn caudally, and then allthe dorsal rootlets coming into that part of the cord lying between the level oftransections are severed bilaterally (Fig. lA).Expecting to be able to determine whether or not the isolated spinal cord,thus prepared, has an ability to excite automatically, electromyograms are taken2711Hukuhara et al.: Automatic activies of the spinal cord concerned with theProduced by The Berkeley Electronic Press, 1960272 T. HUKUHARA, 1. SUMI and S. KOTANIFig. 1. Schematic drawing for the explanation of partial i~lation of the spinal l..'ord.A BUlA : Thoracic part isolated from the rest of the spinal cord of the dog; all the dorsalroots of that part are severed. B: Part shadowed by slanting lines in the right thoracicwall corresponds to the isolated part of the spinal cord.from the intercostal muscles in the intercostal spaces (Fig. 1 B) which correspondto the isolated part of the cord. Details for the recording of electromyogram aredescribed in the previous paper7 •Considering some possible influence of acute injuries upon the spinal cordactivity, a series of experiments is also carried out on the animal whose spinalcord has been isolated aseptically about 10 to 14 days before the experiments.RESULTS AND DISCUSSIONA. Effects of decapitation upon the respiratory movements in the new-born or infant animals.Respiratory movements both in the nostrils or larynx and thorax are abruptlyinterrupted for about 5 to 30 seconds when the animal is decapitated. Then ab-rupt, short-lasting opening of the mouth coincidentally with the opening ofnostrils and caudal shifting of larynx occurs recurrently. In the thorax and ex-tremities, which have already lost their nervous connections to the respiratorycenters involved in the brain stem, there also recurrently occur convulsivemovements whose rhythm is, however, different from that of the movementsobserved in the neck and head. Concordant with these movements of thoraxthere is noted a remarkable widening and narrowing of intercostal spaces, there-fore they can undoubtedly be conceived as respiratory movements. The move-ments are in general more vigorous but less frequent than those observed beforethe decapitation (Fig. 2 A and B). Some 20 to 30 seconds later the movementsrapidly begin to wane until they finally disappear. On the other hand, electro-myograms of the intercostal muscles exhibit bursts of impulses with the rhythmof thoracic movements as shown in Fig. 3.The results described above may suggest the presence of automaticity in thespinal cord, at least in newborn or infant animals.2Acta Medica Okayama, Vol. 14 [1960], Iss. 4, Art. 6http://escholarship.lib.okayama-u.ac.jp/amo/vol14/iss4/6Automatic Activities of Spinal Cord 273Fig. 2. Changes of the respiratory movements produced by decapitation in two rabbits.ABA and B show the breathings before and after the decapitation respectively. Afterdecapitation, an increased amplitude of the movements both in A and B, however, a dec-reased frequency in A, and no remarkable change in B are noticed. Inspiration upwards.Fig. 3. Electromyogram led from the intercartilaginous muscles of a decapitatednewborn rabbit.1 sec.There are observed three burst of impulses corresponding to the phasic thoracic movements.B. Effects of transection of the spinal cord at the medullo-spinal junc-tion upon the respiratory movements in the adult animals.When the spinal cord is transected at the medulla-spinal junction, therhythmical opening of the nostrils and contraction of the laryngeal muscles per-3Hukuhara et al.: Automatic activies of the spinal cord concerned with theProduced by The Berkeley Electronic Press, 1960214 T. HUKUHARA, I. SUMI .and S.KOTANIABFig. 4. Effects of the transection of the spinal cord at the medullo-spinal junction uponthe respiratory movements both in the nostril (upper trace) and in the thorax (lowertrace) in an adult dog. During the period as indicated by a straight line the transectionis pedormed. The movements do not stop in the nostril but these stop in the thoraxinstantaneously. Inspiration downwards in A and upwards in B.sist. These movements are, however, remarkably reduced in frequency andprolonged in duration, waning gradually until they completely disappear, soonafterwards giving place to a sequence of another type of respiratory movements,gaspings (Fig. 4 A). On the other hand the thoracic respiratory movementsabruptly cease arid -no longer reappear (Fig. 4 B). Nevertheless the electromyo-gram reveals that a few impulses are discharged sporadically (Fig. 5).Fig. 5. Electromyogram led from the internal intercostal muscle in'an: adult dog.A B._ _----'---...__--.....-'rr-----......---1 sec. 1 sec..A as well as B shows the electromyogram before and after the spinal transection at themedullo-spinal junction. The thorax is apparently quiet after the transection, nevertheless spikesare discharged sporadically. Upper trace indicates the thoracic movements, expiration down-wards.C. Electrical activities' of intercostal muscles in the animal with acutelyisolated spinal cord.In the animal in which a part of the spinal cord lying between Th7 to4Acta Medica Okayama, Vol. 14 [1960], Iss. 4, Art. 6http://escholarship.lib.okayama-u.ac.jp/amo/vol14/iss4/6Automatic Activities of Spinal Cord 275ThlO is isolated by rostral and caudal spinal transections and by complete seve-rance of all the dorsal rootlets the electrical activities of intercostal muscles arerecorded from each intercostal space corresponding to the isolated spinal. cordsegment respectively.In the 7th intercostal space there can be observed, unexpectedly, the b.urstsconsisting .of a few impulses recurring with respiratory rhythm, although thespinal segment corresponding to the region must be involved within the isolatedpart of the spinal cord. The phenomenon naturally suggests that a minute num-ber of motor nerve fibers coming from the 6th thoracic segment, whose connec-tion with the normal respiratory centers is kept intact, distribute to the intercostalspace mentioned above via the 7th intercostal nerve. On the other hand, in the8th to 10th interc03tal spaces the spikes are discharged sporadically with intervalsvarying from 0.15 to 3.0 seconds without showing any respiratory change (Fig.6 B).Fig. 6. Electromyograms led from the intercostal muscles in the intercostal spaceswhich correspond to the isolated part of the spinal cord.ABlsec.Cat, 1 day old. A: Respiratory bursts of action potentials led from the intercartilagi-nous muscles in the 6th intercostal space (control). B: Spontaneously produced actionpotentials led from the intercartilaginous muscles in the 8th intercostal space.D. Electrical activities of intercostal muscles in the animal with chroni-cally isolated spinal cord.In another series of experiments the isolation of a part of the spinal cordhas been carried out 10 to 14 days before the experiments for the purpose ofexcluding a possibility of such spike discharges as above described from originat-ing in the sites suffering from injury produced by the operative ptocedure, thatis, spinal transection and dorsal root severance.The results are similar to those obtained in the acute experiments, that is,the sporadic spike discharges are recorded from the intercostal muscles in the 8th5Hukuhara et al.: Automatic activies of the spinal cord concerned with theProduced by The Berkeley Electronic Press, 1960276 T. HUKUHARA, I. SUMI and S. KOTANIFig. 7. Action potentials led from the intercostal muscles in the intercostal spaces whichcorrespond to the isolated part of the spinal cord.1 sec.Cat, adult. The isolation of the spinal cord has been carried out 14 days before the ex-periment. A: A burst of respiratory action potentials led from the intercartilaginous mus-cles in the 6th intercostal space (control). B: Spontaneously produced action potentials ledfrom the intercartilaginous muscles in the 8th intercostal space.to 10th intercostal spaces, as shown in Fig. 7 B. The discharges are free fromthe reflex inhibitory influence of skin pinching7 and disappear totally providedthe intercostal nerves innervating the muscles are cut. This suggests that thespike discharges are produced by impulses which spontaneously originate in thespinal cord isolated.SUMMARY1. After spinal transection at the medulla-spinal junction the thoracic res-piratory movements no longer appear in the adult animals, nevertheless thesporadic spike discharges can be recorded from the intercostal muscles.2. Both in the acute and chronic experiments the spinal cord is transectedat the two levels of Th7 and Thl1 respectively and all the dorsal rootlets cominginto that part of the cord lying between the transections are severed. The spora-dic spike discharges with irregular intervals varying about 0.5 to 3.0 sec. can berecorded from intercostal muscles in the 8th to 10th segments of the spinal cordisolated. There can never be found any reflex influence of the skin stimulationupon the discharges, which also disappear provided the intercostal nerves inner-vating the muscles are severed.3. From these results it may be concluded that the spinal cord is endowedwith an ability to initiate the impulses autochthonously to excite the intercostalmuscles, even though it is only poorly developed in the adult animals.REFERENCES1. KOTANI, S. Spinal reflex of intercostal muscles. J. PhysioJ. Soc. Japan. 21, 977-980,1959.2. LANGENDORFF, O. Studien uber die Innervation der Athembewegungen. 1. Mitt. Ueberdie spinalen Centren der Atmung. Arch. f. Physiol. 518 -549, 1880.3. MARCKWALD, M. Die Athembewegungen und deren Innervation beim Kunim:hen. Z. BioI.6Acta Medica Okayama, Vol. 14 [1960], Iss. 4, Art. 6http://escholarship.lib.okayama-u.ac.jp/amo/vol14/iss4/6Autr,matic Activities of Spinal Cord 27723, 149--283, 1887.4. }{OKITANSKY. Untersuchungen uber AthemncIven. \ViencI med. Jahrb. S. 30, quoted fromRosenthal, ]. (5) S. 248, 1874,5. ROSENTHAL, ]. Die Physiologie der Athembewegungen und der Innervation desselben. Her-mann's Handb. d. Physiologic, lld. 4, 11. Tcil, 165- -286, Leipzig, Verlag von F. C. W.Vogel, 1882.6. V. Schroff. Ueber spinale Athemcentra. Wiener med. Jahrb. S. 324, 1875. quoted fromRosenthal, (5) S. 248.7. Sumi, T. and Kotani, S. Excitatory and inhibitory reflexogenic skin areas for the intercostalrespiratory neurons in the dog. Acta Med. Okayama. 13, 301-313, 1959.7Hukuhara et al.: Automatic activies of the spinal cord concerned with theProduced by The Berkeley Electronic Press, 1960

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