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MOTOR EFFECT OF THE DISTAL COLON CAUSED BY STIMULATING THE DORSAL ROOTS OF THE DOG'S LUMBAR NERVES

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MOTOR EFFECT OF THE DISTAL COLON CAUSED BY STIMULATING THE DORSAL ROOTS OF THE DOG'S LUMBAR NERVES TAKEHIKO SEMBA* Department of Physiology, School of Medicine, Hiroshima University, Hiroshima The hypogastric
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MOTOR EFFECT OF THE DISTAL COLON CAUSED BY STIMULATING THE DORSAL ROOTS OF THE DOG'S LUMBAR NERVES TAKEHIKO SEMBA* Department of Physiology, School of Medicine, Hiroshima University, Hiroshima The hypogastric nerve has been almost universally stated to be the inhibitory nerve of the colon (Gaskell, 1920, Garry and Gillespie 1955), however, at times, investigators have also noted a motor effect (Courtade and Guyon 1897, Carlson 1930). In our previous work, both the motor and inhibitory responses of the distal colon were noted to be caused by hypogastric and lumbar colonic nerve stimulation (Semba et al. 1955a). We examined the conditions which might produce motor or inhibitory effects to the colon from both the colonic side and from the side of the stimulation, however, absolute conditions capable of producing reversal of sympathetic action could not be found on either side (Semba et al. 1955a). On the other hand, from the experiment on the ileo-colonic motor reflex and the experiment on the colonic motor effect which was produced by cenral stimulation of the splanchnic nerve, we confirmed the motor efferent nerves to be the hypogastric and lumbar colonic nerves (Semba et al. 1955b and c). Thus, I am suggested that the motor effect of the colon is not a reversal response of the inhibitory nerves, and that the motor and inhibitory effects are produced by the action of functionally differrent fibers. Kure and his co-workers (1931) have already reported in the spinal parasympathetic on the motor fibers acting through the dorsal roots. However, this theory is based mainly on histoloical data, not on physiological research, therofore, it encountered many objections such as Hukuhara (1935) and Hinsey (1933). The behaviour of the distal colon influenced by stimulation of the lumbar nerve roots has not yet been examined physiologically and so the present study was undertaken to examine the effects obtained by stimulating the dorsal and ventral roots of the lumbar nerves. METHOD Unanesthetized spinal dogs (the spinal cord was transected between the cervical and thoracic regions hours previously) and anesthetized dogs (hexamethyl-barbital 0.05mg/kg. body weight, injected intravenously) were used in all experiments. The behaviour of the distal colon was recorded on the kymograph by using the balloon tambour system. The general blood pres- Received for publication August 21, 1956. T. SEMBA sure was measured at the carotid artery by a mercury manometer. The peripheral cut end of the dorsal root and the ventral root of the lumbar nerves were stimulated by galvanic or faradic current. Then the lumbar sympathetic chain, inferior splanchnic nerves, lumbar colonic nerve and the hypogastric nerves were also stimulated. To block the ganglion, a nicotine solution (1in solution, Merck ) or hexamethonium bromide (C6) (methobromine5-10 mg/kg. body weight, intravenously injected) was used. RESULTS 1) The peripheral stimulation of the ventral root (L2-L7) constantly caused decrease of colonic motility and tone, however, motor activity was never elicited (see Fig.1A). This phenomenon was connected in no way with activity or inactivity of the colon and dissection of the pelvic nerves. On the other hand, peripheral stimulation of the dorsal root from the2nd to the7th lumbar nerves, caused a contraction of the colon after a few seconds latency, and as an aftereffect, a temporary inhibition usally followed (fig.1b). The stimulation of the 3rd, 4th and5th lumbar nerves was the most effective. Motor activity of the colon produced by dorsal root stimulation was more readily obtainable with the colon having increased tone and peristaltic movement. After administration of a0.1per cent solution of eserine sulphate, the motor response was more easily obtained by stimulation. In all cases, dorsal root stimulation never produced an inhibitory effect of the colon. The ventral stimulation correlated with the effects on the blood pressure although the dorsal stimulation did not. Above-mentioned results were very similar in both unanesthetized dogs and anesthetized animals. The influence of stimulation of the left ventral (A) and dorsal (B) roots of the4th lumbar nerve on the distal colon. Anesthetized dog. 9cm. (Explanation of curves from the top downward: movement of distal colon, signal, time6secs.) To block the sympathetic ganglion, a Cs-solution was injected intravenously or the nicotine solution (not in large dose) was applied directly to the inferior mesenteric ganglion. The effect of ventral root stimulation was completely abolished, however, in the effect caused by stimulation of the dorsal root, no change were noted. Both the ventral inhibitory and the dorsal motor effect were not blocked in the lumbar sympathetic chains. No stimulating motor effects were observed after the injection of a1in 1,000solution of atropine. MOTOR RESPONSE OF COLON 2) The left lumbar sympathetic chain was dissected, and its peripheral end was stimulated at the2nd, 3rd and4th lumbar regions. The inhibitory effect was, in general, observed immediately after the stimulation (fig.2a). This effect was also obtained after interruption of all communications between the spinal cord and the sympathetic chains. Sometimes, the motor effect was obtained by stimulating the sympathetic chain. However, the reverse effect to sympathetic nerve stimulation always occurred after administration of nicotine to the inferior mesenteric ganglion or after injection of a Cs-solution, namely, a purely motor effect was obtained as seen in fig.2b, and the inhibitory effect could not be observed at all. The motor effect of the distal colon by the stimulation of the inferior splanchnic nerves also persisted after block of the inferior mesenteric ganglion as seen in fig.2c. The influence of stimulation of the left sympathetic chain (A, B) and the inferior splanchnic nerves (C) on the distal colon. Anesthetized dog. C.D.=8cm. A: normal, B: 3.5 minutes after nicotine-application to the inferior mesenteric ganglion. C: 11.5minutes after nicotine-application. 100mm. Hg. (Explanation of curves from the top downward: general blood pressure, movement of distal colon, signal, time6secs.) The influence of stimulation of the inferior splanchnic nerves (A,B), the lumbar colonic nerve (C) and the hypogastric nerves (D) on the distal colon. Anesthetized dog. C.D.=8cm. A: normal, B: 1.5minutes after nicotine-application to the inferior mesenteric ganglion, C: 4.5minutes of ter, D: 9minutes after. 130mm. Hg. (Explanation of curves is the same in fig.2). T. SEMBA 3) The peripheral ends of the severed inferior splanchnic nerves (all the spinal rami and the coeliac rami of the inferior mesenteric ganglion) were stimulated in the normal dog. In general, the inhibitory effect was obtaind as seen in fig.3a. However, after the block of the inferior mesenteric ganglion. by nicotine-application or administration of a Cs-solution, stimulation of the inferior splanchnic nerves caused the reversal of the inhibitory effect, that is, the purely motor effect was obtained (fig.2 C and fig.3 B). Further, it was noticeable in this example that by the stimulation of the post ganglionic fibers to the inferior mesenteric ganglion (hypogastric and lumbar colonic nerves), the inhibitory effect was also obtained as seen in fig.3c and D. DISCUSSION 1) The effect of the ventral and dorsal root stimulation of the lumbar nerves on the distal colon was clearly determined in Exp. 1as shown in fig.1a and B, namely, a uniformly inhibitory effect was obtained by ventral root stimulation and a purely motor effect by dorsal root stimulation. The inhibitory effect due to the ventral root stimulation has never reversed to the motor effect in any condition. Kure et al.(1931) had already demonstrated in his spinal parasympathetic, the existence of the motor fibers via the dorsal roots, however, he has not yet confirmed the motor effect to the colon which is innervated by the pelvic nerves (motor nerves to the colon) on the physiological basis. In the present experiments, the motor effect was obtained by stimulation of the dorsal roots from the 2nd to the 7th lumbar nerves, especially the 3rd, 4th and 5th lumbar nerves. The motor effect was augmented by administration of a eserine solution, and abolished by atropine injection. These observations further suggest that the motor nerve via the dorsal root is the cholinergic nerve (Malmejac et al. 1940a and b). 2) The inhibitory effect caused by ventral root stimulation was abolished after administration of the ganglion-blocking agent. However, the motor effect of the dorsal root was not influenced at all (see Exp. 1). And also after blocking the inferior mesenteric ganglion, a purely motor effect was obtained instead of the inhibitory effect produced by stimulation of the lumbar sympathetic chain and inferior splanchnic nerves (see Exp. 2 and 3). According to the work of Langley (1896), these results obtained from the above experiments show that the inhibitory fibers to the colon are connected with the nerve-cells in the inferior mesenteric ganglion, however, the motor fibers have no nerve-cells in it. The inhibitory fibers to the colon also do not contain any nerve-cells in the ganglia of the sympathetic chain, as shown by the fact that the nicotine-application to the sympathetic chain do not alter the effect to the distal colon of the ventral root stimulation. And so it can be said that in normal dogs, stimulation of these nerves convey both inhibitory or motor effect to the colon under certain condition. 3) The motor effect of the colon caused by stimulating the dorsal root is probably due to the motor nerve . The word motor nerve is used in order MOTOR RESPONSE OF COLON to differentiation from the inhibitory nerves in the present paper. However, whether the above-mentioned results are due to the action of genuine motor fibers or the antidromic action of the sensory nerve stimulation (Bayliss1901) which is not yet fully clarified, is the further materials for future investigation. Kure and his co-workers (1931) intended to determine the motor fibers on a histological basis, however, few data from the physiological standpoint. But as mentioned in the introduction of this paper, from studies on the motor effects of central stimulation of the splanchnic nerve (Semba and Mishima1955b) and on the motor reflex from ileum to colon (Semba and Sasaki1955c), it was found that the motor efferent nervous pathways to the colon were the sympathetic nerves such as the hypogastric and lumbar colonic nerves. Thus it can be surmised that a motor efferent pathway via the dorsal root may exist physiologically. SUMMARY The influence of stimulation of the lumbar ventral root and the dorsal root on the distal colon has been investigated. The chief results thus obtained may be summarised as follows: 1) In anesthetized and unanesthetized dogs, peripheral stimulation of the ventral root (L2-L7) constantly caused an ihibitory effect of the distal colon, and the dorsal root stimulation (L2-L7) caused always a motor effect. However, the reverse effect did not occurred under any condition. 2) The effect of ventral stimulation was abolished after blocking the inferior mesenteric ganglion by application of nicotine or a C6-solution. However, the effect of dorsal root stimulation was not influenced by the block of the ganglion. This shows that the inhibitory fibers have nerve-cells in the inferior mesenteric ganglion, however, the motor nerve do not have any nerve-cell connections in it. 3) The motor effect is augmented by eserine solution and abolished by atropine. REFERENCES 1. BAYLISS, W. M. On the origin from the spinal cord of the vaso-dilator fibers of the hind limb and on the nature of these fibers. J. Physiol. 26: 173, CARLSON, A. J. The extrinsic nervous control of the large bowel. J. Amer. Med. Ass. 94: 78, COURTADE, D. AND GUYON, J. F. Influece motorice du grand sympathique et du nerf erecteur sacre sur le gros intestin. Arch. Physiol. nor. et path. 29: 880, GARRY, R. C. AND GILLESPIE, J. S. The responses of the musculature of the colon of the rabbit to stimulation, in vitro, of the parasympathetic and of the sympathetic outflows. J. Physiol. 128: 557, GASKELL, W. H. The Involuntary Nervous System London: Longmans, Green and Co., HINSEY, J. C. On the absence of spinal parasympathetic fibers in the dorsal spinal nerve roots in the cat. Amer. J. Physiol. 105: 51, HUKUHARA, T. Is the small intestine innervated by the so-called spinal parasympathetic nervous system? Quart. J. exp. Physiol. 24: 37, 1935. T. SEMBA 8. KURE, K., ICHIKO, K. AND ISHIKAWA, K. On the spinal parasympathetic. Physiological significance of the spinal parasympathetic system in relation to the digestive tract. Quart. J. exp. Physiol. 21: 1, LANGLEY, J. N. On the nerve cell connection of the splanchnic nerve fibers. J. Physiol. 20: 223, MALMEJAC, J., DONNET, V. AND MONGES, H. Action des nerfs extrinseques de l'estomac sur la motricite gastrique. C. r. Soc. Biol. 133: 478, 1940a. 11. MALMEJAC, J. AND DONNET, V. Sur l'origine et le trajet des fibres cholinergiques a destination gastrique contenues dans les nerfs splanchniques. C. r. Soc. Biol. 133: 482, 1940b. 12. SEMBA, T., MISHIMA, H. AND SASAKI, H. The influence of the hypogastric nerves on the distal part of colon. J. Physiol. Soc. Japan 17: 777, 1955a. 13. SEMBA, T. AND MISHIMA, H. The contraction of the distal colon caused by central stimulation of the splanchnic nerves. J. Hiroshima Med. Ass. 8: 188, 1955b. 14. SEMBA, T. AND SASAKI, H. On the ileo-colonic excitatory reflexes. Soogo-Igaku12: 585, 1955c.
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