Visceral Receptors and Their Afferents in the Caudal Mesenteric Nerve of the Duck
TL;DR: The behaviour and reactivities of visceral receptors to different mechanical and chemical stimuli in simple unit preparations from the caudal mesenteric nerve of adult ducks were studied to examine the physiological roles of such receptors.
Abstract: 1. The behaviour and reactivities of visceral receptors to different mechanical and chemical stimuli in single unit preparations from the caudal mesenteric nerve of adult ducks were studied to examine the physiological roles of such receptors. 2. In total, 83 single unit activities were recorded from the caudal mesenteric nerve. 3. Receptors were grouped according to their locations in different layers of the rectum as (i) over the branching points of the blood vessel or in the serosal layer, (ii) in the muscle layer or (iii) in the mucous membrane of the rectum. 4. All the receptors, both spontaneous and non‐spontaneous, responded to mechanical probing. Receptors of the muscle layer responded to distension also and showed a slowly‐adapting nature. Most of the receptors of the other two groups were of the rapidly‐adapting type. 5. Conduction velocity ranged from 0.76 to 34.6 m/s. 6. Sympathetic afferent fibres from the hind gut ascend along the intestinal nerve and join the caudal mesenteric nerve via the...
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TL;DR: The behavioural reactivity of the visceral receptors and their afferents in the caudal sympathetic nerve (part of synsacral sympathetic chain) of domestic duck was studied using electrophysiological techniques to examine their involvement in different physiological functions.
Abstract: The behavioural reactivity of the visceral receptors and their afferents in the caudal sympathetic nerve (part of synsacral sympathetic chain) of domestic duck (Anas platyrhynchos) was studied using electrophysiological techniques to examine their involvement in different physiological functions. In total, 114 single unit activities were recorded from the caudal sympathetic nerve of duck. Receptors were classified according to location: in the anal sphincter (32 units), in the mucous membrane of the cloaca (45 units), at the branching point of the blood vessels over the rectum and adjacent mesentery (10 units), at the base of the feather follicles in and around the vent (17 units), and in the ventral and lateral lower abdominal wall muscle (10 units). Both spontaneous and non-spontaneous receptors responded to mechanical stimuli; average frequency of discharge of non-spontaneous units being much higher. Most of these receptors were of the rapidly-adapting type. Only some receptors in the abdominal muscle layer, anal sphincter and mucous membrane of hind gut were of the slowly-adapting type. Some of the latter responded to intraluminal distension pressure. Except for responses to succinylcholine chloride by receptors in the abdominal wall muscles and some units in the external anal sphincter, mechanosensitive receptors were not responsive to chemical stimuli. The discharge rate of the receptors at the base of the feather follicles varied according to the strength of stimulus. Conduction velocity of the caudal sympathetic afferent fibres ranged from 2.5 to 45 m/sec.
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945 citations
TL;DR: The existence of receptors in the abdominal and pelvic viscera of mammals has long been known from the reflex responses which can be elicited by a variety of experimental procedures, but no attempt has been made to establish whether the activity is related to muscle tension and, if so, whether the receptors are 'in parallel' or 'in series' with the muscle fibres.
Abstract: The existence of receptors in the abdominal and pelvic viscera of mammals has long been known from the reflex responses which can be elicited by a variety of experimental procedures (Ranson, 1921; Irving, McSwiney & Suffolk, 1937). Hurst (1911) made an extensive clinical study of the sensibility of the alimentary canal, and concluded that a form of 'muscle-sense' existed in all parts of the alimentary canal, but did not further investigate the receptors. Afferent impulses from gastric and intestinal receptors of the cat have been recorded in the splanchnic nerves and in fine mesenteric nerve strands by Gernandt & Zotterman (1946) and in the cervical vagus by Paintal (1954). Impulses in hypogastric and pelvic afferent fibres from bladder receptors of the cat have been recorded by Evans (1936) and of the dog by Talaat (1937). It has been customary to regard the sense endings as stretch receptors, but no attempt has been made to establish whether the activity is related to muscle tension and, if so, whether the receptors are 'in parallel' or 'in series' with the muscle fibres. The problem has been re-investigated by recording from single afferent fibres in the cervical vagus and the pelvic plexus. Particular attention has been directed to the discharge in single fibres during distension and contraction of the viscera and to the size of the afferent fibres. A preliminary account of this work has been published (Iggo, 1954).
496 citations
TL;DR: It is shown conclusively that food intake in dogs is influenced to a large extent by distension of the stomach whether the distension is achieved mechanically by a balloon or by calorically inert food.
Abstract: A number of investigators have shown that reflex respiratory, pupillary or vascular effects are produced by stimulating the central end of the vagi below the diaphragm (Brodie & Russell, 1900; Neumann, 1914; Carlson & Luckhardt, 1921; Harper, McSwiney & Suffolk, 1935), although these observations do not indicate that nerve fibres of the stomach are involved. However, Irving, McSwiney & Suffolk (1937) have shown clearly from a study of pupillary responses that sensory impulses in the vagus are produced when the stomach is distended. The presence of myelinated afferent fibres in the vagus at the level of the diaphragm was pointed out by Edgeworth (1892) and confirmed by Langley (1892). Evidence for spindle-shaped endings in the stomach has been provided by the histological studies of Langworthy & Ortega (1943) who showed that they are connected to myelinated fibres thought to be sensory in function. In spite of these studies, impulses from afferent fibres of the stomach have been recorded only recently (Paintal, 1953c). These were in fact found in the course of an investigation into the normal function of receptors stimulated by phenyl diguanide (Paintal, 1954a). Since then these gastric stretch receptors have been studied further, and several interesting facts regarding their responses to mechanical stimuli and drugs have emerged. Their responses to drugs are described in another paper (Paintal, 1954b). Recent studies (Janowitz & Grossman, 1949; Share, Martyniuk & Grossman, 1952) have shown conclusively that food intake in dogs is influenced to a large extent by distension of the stomach whether the distension is achieved mechanically by a balloon or by calorically inert food. Further, distension of the stomach with a water-filled balloon inhibits sham drinking, a reflex that is * Present address: Vallabhbhai Patel Chest Institute, University of Delhi, Delhi, India. 17 PHYSIO. CXXVI
258 citations
TL;DR: Evidence is presented for the conclusion that most of the fibres isolated in the cat were probably unmyelinated, as well as new methods for identifying single fibres in a multifibre strand described.
Abstract: Although there are many unmyelinated afferent axons in the peripheral nerves of mammals there is very little known either about their behaviour or about the receptors with which they are connected. Myelinated fibres, on the other hand, have frequently been studied as single units. This situation is due to the difficulty of isolating the unmyelinated fibres as single units for electrophysiological recording. Activity in unmyelinated afferent fibres has been recorded in multifibre preparations, notably by Zotterman (1939) and Maruhashi, Mizuguchi & Tasaki (1952). Only occasionally did these authors succeed in analysing activity in individual fibres. Douglas & Ritchie (1957a, b) have recently succeeded in detecting C fibre activity in whole nerves. Because of this lack of information about individual unmyelinated fibres it was decided to follow up the observation (Iggo, 1956b) that afferent fibres with conduction velocities as low as 1-3 m/sec could be isolated as single units from the cervical vagus of the goat. In addition to measurements of conduction velocity other tests were used in an attempt to decide whether the fibres were unmyelinated. New methods for identifying single fibres in a multifibre strand are described. With the aid of these methods and by refinements of the usual dissection methods very slowly conducting fibres have now been isolated in the cat. Evidence is presented for the conclusion that most of these fibres were probably unmyelinated. Preliminary reports have already appeared (Iggo, 1956 b, 1957 c). The gastric and intestinal receptors for which these figures were the centripetal axons are described elsewhere (Iggo, 1957a, b).
183 citations
TL;DR: The receptors were distension-sensitive endings in the œsophagus, stomach or small intestines, and probably lay in the muscularis externa of the stomach or intestines.
Abstract: 1. Electrical activity was recorded in single afferent C fibres dissected from the cervical vagus of the cat. The receptors were distension-sensitive endings in the œsophagus, stomach or small intestines. The latency of the response to distension was largely due to the time taken for the impulses to travel from the receptor to the recording electrodes.
2. The rate of discharge of impulses was much higher when distension with the same volume of fluid was rapid than when distension was slow. This was seen most clearly when only short lengths of the intestine were distended. It is suggested that the effect is partly due to smooth muscle tone.
3. Contraction of smooth muscle at the site of the receptor set up a discharge of impulses in the afferent fibre, and this response was not dependent on changes in intraluminal pressure. It was concluded that the receptors were tension-signalling devices “in series” with the contractile elements in the smooth muscle.
4. The receptors were unaffected by removal of the mucosa and submucosa, and probably lay in the muscularis externa of the stomach or intestines.
5. The receptors were excited by intravenous injection of phenyl-diguanide and adrenaline and by acetylcholine poured over the opened viscus. They were unaffected by 0·1N HCl. The difficulty of interpreting the action of ACh was pointed out.
178 citations