Disruption of the jejunal migrating motor complex by gastric distension and feeding in the dog

1. The jejunal motor response to gastric distension has been quantified in the conscious dog and compared with that of feeding in order to determine the role of the physical bulk of a meal in the conversion from fasted to fed motor activity. 2. In six dogs gastric distension abolished the cyclical migrating motor complex (m.m.c.) and evoked a pattern of continuous irregular jejunal motility similar to that seen postprandially, but only after a latency of 21.5 +/- 2.7 min compared to that of 7.1 +/- 1.2 min for the response to feeding. Computer analysis of distension and fed jejunal motility revealed similar distributions of intervals between contractions and contraction amplitudes with comparable mean values for both. 3. In two dogs with antrum and corpus surgically divided distension of the corpus had a similar effect on jejunal motility although the latency to both distension and feeding were considerably less. 4. By varying the period of distension it has been possible to control accurately the duration of the jejunal motor response and so assess its effectiveness in disrupting the timing of the m.m.c. The return to m.m.c. cycling following deflation was independent of preceding complexes. The occurrence of the post-distension activity front was closely related to the act of deflation itself (R = 0.94) following a latency of 26.2 +/- 2.1 min (n = 39). 5. It is concluded that the bulk of a meal contributes significantly to the early part of postprandial motility and is capable of disrupting the timing of subsequent migrating motor complexes.

Involvement of gastrointestinal mechano- and intestinal chemoreceptors in vagal reflexes: an electrophysiological study

The role of gastrointestinal mechanoreceptors and intestinal chemoreceptors in the genesis of vago-vagal reflexes was assessed by recording single vagal efferent fibre discharge in the urethane-anaesthetized ferret during procedures known to activate discrete populations of gastrointestinal afferent fibres. Distension of the stomach, duodenum and jejunum was used to activate mechanoreceptors while perfusion of the intestinal loops with various chemical solutions was used to activate mucosal chemoreceptors. Mechanical stimulation of the stomach and/or intestine was effective in modulating vagal efferent discharge in 90% of units tested. The response (either excitation or inhibition of efferent firing) was characterized by its short-latency (less than 1 s), slow-adaptation, and rapid return on removal of the stimulus. In contrast, chemical stimulation was much less potent evoking clear-cut responses in only 26 of the 109 efferent units. Luminal HCl was the most effective stimulus accounting for 81% of the efferent responses although these were of long-latency (greater than 1 min), gradual in onset and poorly maintained. Other efferent responses to HCl and hypertonic saline were characterized by a long-latency, sudden increase in discharge associated with the prodrome of vomiting. We conclude that while the mechanosensitive afferent input is well represented in terms of the genesis of vagal reflexes, the chemosensitive afferent input may be more important in behavioural aspects of visceral stimuli like vomiting.

Vagal afferent discharge from gastric mechanoreceptors during contraction and relaxation of the ferret corpus

Vagal afferent fibres with mechanoreceptive fields in the gastric corpus were studied electrophysiologically in the urethane-anaesthetized ferret in an attempt to assess how changes in muscle tension and length modulate receptor discharge. Single afferent units were spontaneously active and increased their firing on distension of the corpus. During vagally evoked isovolumetric contractions and relaxations, the afferent discharge closely followed changes in intracorpus pressure. Under near-isotonic conditions, changes in both intracorpus pressure and afferent discharge were attenuated to similar degrees despite large changes in corpus volume, although the latter had a modulating influence on afferent discharge. These mechanoreceptors appeared to behave as tension receptors but were also influenced by muscle length as would occur if the receptor were associated with the laminar intramuscular septa of connective tissue which may serve as intramuscular tendons in this tissue.

A permissive role for the vagus nerves in the genesis of antro-antral reflexes in the anaesthetized ferret

1. The role of the vagus nerves in the genesis of antro-antral reflexes was investigated in the urethane-anaesthetized, splanchnectomized ferret. 2. Antral distension stimulated antral contractions with a threshold volume of 3.5 +/- 0.9 ml (corresponding to an intra-antral pressure of 0.27 +/- 0.11 kPa) by a vagal-dependent mechanism as indicated by the attenuated response seen during vagal blockade by cooling. Atropine (1 mg/kg) abolished the antral response to distension. 3. In vagotomized animals, close arterial infusions of acetylcholine at a dose sufficient to return antral motility to basal levels led to the reappearance of the reflex. Low-frequency electrical stimulation of the preganglionic vagal neurones had a similar effect. These effects were also abolished by atropine (1 mg/kg). 4. Hexamethonium (10-25 mg/kg) suppressed the potentiating effect of acetylcholine, indicating a ganglionic site of action. The attenuated response to antral distension seen in vagotomized animals in the absence of exogenous acetylcholine or electrical vagal stimulation was not sensitive to hexamethonium but abolished by atropine (1 mg/kg). 5. The results are consistent with the vagus performing a permissive role in the genesis of antro-antral reflexes mediated through local enteric pathways.

Evidence for a non-cholinergic excitatory innervation in the control of colonic motility

The colon of the ferret anesthetized with urethane exhibits two distinct types of motility patterns. These were abolished or considerably reduced by blocking nervous conduction in the vagus nerves by cooling to below 4 degrees C. Atropine transiently abolished motility which on its return was also found to be sensitive to vagal integrity. Electrical stimulation of either the cut central or peripheral end of a branch of the abdominal vagus caused large amplitude contractions of the colon which were not blocked by atropine or by atropine and a combination of alpha- and beta-adrenoceptor blocking agents. These results are consistent with either two separate motor pathways to the colon in the vagus nerve, one cholinergic, the other non-adrenergic, non-cholinergic, or a single pathway with the effects mediated by a primary and a co-transmitter. They also demonstrate that "spontaneous activity" is driven in part by both cholinergic and non-cholinergic mechanisms.

ABC of spinal cord injury. Later management and complications--I

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ABC of spinal cord injury. Transfer of care from hospital to community

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ABC of spinal cord injury. Social needs of the patient and his family

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ABC of spinal cord injury. Occupational therapy

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ABC of spinal cord injury. Physiotherapy

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ABC of spinal cord injury. Nursing

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ABC of spinal cord injury. Urological management

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ABC of spinal cord injury. Medical management in the spinal injuries unit

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ABC of spinal cord injury. Early management and complications--II

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ABC of spinal cord injury. Early management and complications--I

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The response to isoniazid of action tremor in multiple sclerosis and its assessment using polarised light goniometry

Isonicotinic acid hydrazide (isoniazid) was evaluated in five patients as a treatment for the control of severe cerebellar action tremor occurring in multiple sclerosis. Oral doses of isoniazid BPC were increased every 2 weeks from 300 mg to 1200 mg daily over an 8 week period. Four patients reported considerable symptomatic benefit at doses ranging from 600 mg to 900 mg daily. Polarised light goniometry demonstrated a two to three-fold reduction of tremor in these patients when standard methods of clinical assessment showed only marginal improvement.

ABC of spinal cord injury. Radiological investigations

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ABC of spinal cord injury. Evacuation and initial management at hospital

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ABC of spinal cord injury. At the accident

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The effect of intraluminal tryptophan and phenylalanine on small intestinal motility in the conscious dog

The effect of D- and L-isomers of tryptophan and phenylalanine on fasting motor activity of canine jejunum were investigated. Only L-tryptophan had any effect on jejunal motility. The concentration of L-tryptophan required to elicit a motor effect in 50% of animals was estimated at 28 mM. 50 mM-L-tryptophan stimulated jejunal motility after a latency of 4.5 +/- 0.7 min. The pattern of motility was similar to that evoked by feeding but continued for only 41 +/- 5 min and failed to disrupt the normal timing of the interdigestive migrating motor complex (m.m.c.). The duration of the subsequent phase II of the complex was, however, significantly reduced. Multiple infusion of L-tryptophan also failed to disrupt the timing of the m.m.c. These data are consistent with the hypothesis that specific breakdown components of protein digestion are implicated in the stimulation of postprandial motor activity. The mechanisms involved in the motor response to L-tryptophan are discussed.