An electrophysiological study of single vagal efferent units associated with gastric movements in sheep

Iggo, A.; Leek, B. F.

doi:10.1113/jphysiol.1967.sp008244

Cited by 51 publications

(50 citation statements)

References 25 publications

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“…Currently held views based on studies of vagal efferent activity are that (biphasic) discharges from gastric centres along what have been described as type I fibres result in the diphasic contraction of the reticulum in anaesthetized sheep (Iggo & Leek, 1967 a). However, it is well known that cyclical contractions of the reticulum in decerebrate (Titchen, 1958(Titchen, , 1960 and anaesthetized preparations (Iggo & Leek, 1967 a) are not readily obtained unless the reticulum or associated structures are stretched. In-series tension receptors are activated and provide afferent stimulation of the gastric centres (Iggo & Leek, 1967 b).…”

Section: Discussionmentioning

confidence: 99%

IN VITRO SPONTANEOUS MOTILITY OF GASTRIC SMOOTH MUSCLES OF THE SHEEP

Wong

McLeay

1988

Exp Physiol

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SUMMARYWhole strips of muscle wall cut parallel to their corresponding longitudinal, circular or internal oblique orientations in the reticulum, rumen, omasal body, abomasal body and antrum and to the muscularis mucosae of the omasal leaves were mounted along a vertical axis and their mechanical activities recorded isometrically. The strips were perfused with Tyrode-Ringer solution at 37°C bubbled with 100% 02 or a mixture of 95 % 02+5 % CO2. Spontaneous activity was observed in muscle strips from all regions but not all muscle strips were spontaneously active: markedly greater spontaneous activity and a greater sensitivity to stimulatory agents occurred with 100% 02. Spontaneous activity was unaffected by the ganglionic blocking agent hexamethonium (10-5 M) whereas atropine (10-6 M) had no effect, or reduced and in some cases with rumen only, abolished activity. Acetylcholine (10-6-10-7 M) caused contraction of all muscle except muscularis mucosae from omasal leaves. Electrical stimulation evoked responses which included atropine-sensitive contractions, relaxations and rebound contraction especially following atropine. The experiments showed that both major muscle layers of the reticulum, rumen, omasum and abomasum in mixed-layer preparations exhibited spontaneous activity when removed from the influence of their cholinergic innervation and this included atropine-resistant diphasic contractions of the internal oblique muscle of the reticulum. The muscularis mucosae of the omasal leaves exhibited spontaneous contractile activity unaffected by cholinergic agonists and antagonists.

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Section: Discussionmentioning

confidence: 99%

IN VITRO SPONTANEOUS MOTILITY OF GASTRIC SMOOTH MUSCLES OF THE SHEEP

Wong

McLeay

1988

Exp Physiol

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“…The role ofvagal efferents has been established in studies associating characteristic contractions of the reticulum and rumen with different patterns of electrical stimulation of the vagus nerve (Dussardier, 1960;Reid & Titchen, 1965). A direct association between gastric and/or oesophageal contractions and impulse traffic in vagal efferent neurones has been shown in conscious sheep by the technique ofcrossed-nerve anastomosis (Dussardier, 1955(Dussardier, , 1963Roman, a, b, 1967 and in anaesthetized animals by direct recording of action potentials in vagal efferent fibres (Iggo & Leek, 1967). Evidence obtained from studies on impulse traffic in afferent vagal fibres in the anaesthetized goat or sheep suggests that the cranial regions of the stomach (Iggo, 1955;Leek, 1969Leek, , 1977 and the caudal oesophagus (Falempin, Mei & Rousseau, 1978) are richly provided with mechano-and/or chemoreceptors.…”

Section: Introductionmentioning

confidence: 99%

Electrophysiological Study of Vagal Afferent and Efferent Units in Conscious Sheep

Rousseau

1984

Exp Physiol

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SUMMARYCrossed-nerve anastomoses were performed to record activity of vagal efferents and afferents during regurgitation and eructation in conscious sheep. Following anastomoses of the central end of a vagus nerve to the peripheral end of a phrenic nerve, discharges in units of the diaphragm reinnervated by vagal efferent neurones were associated with contractions of the caudal oesophagus and of the rumen. During regurgitation in the course of rumination, discharges in oesophageal efferents consisted of a characteristic pattern of two bursts in a constant association with the additional phase of the reticular contraction and the more forceful inspiratory effort. Discharges in two types of units bore a temporal relation with the motor gastric cyles. Early units are interpreted as innervating pillars of the rumen and late units its dorsal wall. Regular patterns of discharge were recorded during successive A sequences of rumen contractions. In contrast, there was a variability of pattern of activity of efferents during B sequences: a constant time relationship was not observed between discharges of both types of units. During B sequences accompanied by eructation, the most characteristic pattern in gastric and oesophageal units had the following features: the impulses in the early units increased in frequency, outlasted the discharge in the late units by 1 s and ended when a brief discharge was recorded in an oesophageal unit at the time of eructation. It is suggested from the patterns of discharge observed in both gastric and oesophageal efferents that the orderly sequence which achieves regurgitation and eructation results from the central co-ordination of efferent output.Following anastomoses of the central root of the nodose ganglion to the peripheral end of the accessory nerve, discharges in units of the mastoido-humeral muscle reinnervated by vagal afferent axons were associated with contractions of the oesophagus and movements of the larynx during swallowing and regurgitation. Discharges in oesophageal afferents coming from the caudal oesophagus were coincident with discharges observed in the vagal efferent fibres innervating this part of the oesophagus. Afferents from the pharynx and the larynx were active at the same time as the nasopharynx and the glottis were demonstrated to be closed. Thus the major characteristic of the afferents the traffic of which has been recorded in cross-sutured sheep in the course of rumination is that their discharges are occurring at the same time as motor events are developing. It has been concluded that in the complex motor events during regurgitation there is a significant afferent input which contributes to the central nervous regulation of their course at any time.

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“…On sait que le cycle moteur des préestomacs débute par la contraction biphasique du réseau suivie par la contraction des piliers et (1958,1960) (Leek, 1963 ; Leek, 1967 (Rousseau, 1984 (lggo, 1955 ;Leek, 1969, ou grâce à des microélectrodes implantées dans le ganglion plexiforme au voisinage des corps cellulaires des neurones sensitifs (Falempin, Mei et Rousseau, 1978). Chez le mouton éveillé, on peut recueillir l'activité d'un récepteur en faisant réinnerver un muscle du cou par les axones sensitifs vagaux, à la suite d'une anastomose entre la racine centrale du ganglion plexiforme et l'extrémité périphérique du nerf spinal-accessoire, nerf moteur de ce muscle.…”

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“…Leur stimulation entraîne une augmentation de la motricité gastrique ; elle est à l'origine des réflexes excitateurs déclenchés par la distension du réseau ou par l'étirement du pli réticulo-ruminal, tant chez l'animal éveillé (Ash et Kay, 1959 ;Dussardier, 1960) que dans les conditions expérimentales aiguës (Titchen, 1960 ;Dussardier, 1960 ; Iggo et Leek, 1967). Ces récepteurs peuvent également renseigner sur le degré de remplissage des réservoirs puisque la fréquence de leur décharge de repos est fonction de la tension pariétale.…”

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