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Item Vagal influences on respiratory reflexes : interaction of P.S.R. and R.A.R. on the inflation and deflation reflex, their role in linking respiratory cycles : and postvagotomy effect of P.D.G. : a thesis in partial fulfilment of the requirements for the degree of Master of Science, Massey University(Massey University, 1985) Jones, HeatherThere is evidence that changes in one respiratory cycle may influence subsequent cycles by a central mechanism. Thus the influence of P.S.R. and R.A.R. activity from within one respiratory cycle on subsequent cycles, which we have called "memory", needed to be examined in the determination of duration of expiration (tE) and inspiration (tI). this study was designed to investigate the relative roles of P.S.R. and R.A.R. stimulation in expiration influencing tI arnd tE over several subsequent breaths. In particular to investigate their role in linking respiratory cycles. In 14 anaesthetized spontaneously breathing rabbits we studied the response of tI and tE to +ve and -ve pressure pulses of 20KPa applied to the lung at various stages in expiration before and during P.S.R. block with S02. Before P.S.R. block, +ve pressure pulses early in expiration generally shortened tE containing the pulse, applied later +ve pressure pulses lengthened tE. Positive pressure pulses after P.S.R. block, and -ve pressure pulses before and after block always shortened tE. Regardless of sign of pulse tE was shortened in subsequent breaths before and after block. The inspiration after negative pulse application was usually lengthened. After effective block -ve pulses rarely lengthened tl. Large shortening of tE containing the pulse was usually followed bv a shortened tl. Positive pulses did not significantly effect the duration of tl. Regardless of sign of pulse tl was not usually changed but occasional large shortening occured in subsequent breaths before and after P.S.R. block. This indicates that the tE containing the stimulation is governed by a balance between P.S.R. and R.A.R. activity. The tI following t.he stimulus is governed by a balance between memory 11 of P.S.R. and R.A.R. activity. In the breaths following both tE and tI were influenced by memory of R.A.R. activity only. However "memory'' of strong R.A.R. activity is required to affect tI. During this study it was intended to use phenyldiguanide (P.D.G.) to test J receptor patency. Intravenous injections of P.D.G. have been used to provoke respiratory reflexes, these have been considered to be due mainly to stimulation of type J receptors. However although most workers demonstrated that vagotomy abolished or reduced these reflexes, some still had significant response to P.D.G. after vagotomy. A study was conducted to resolve this difference and demonstrate the sites at which P.D.G. acts in rabbits. We measured tE and tI in 10 anaesthetized spontaneously breathing rabbits. 50 g/kg P.D.G. was given intravenously (via a catheter with its tip close to the right atrium) to the intact rabbit; after blocking epicardial receptors; immediately after bilateral cervical vagotomy; 15 minutes after vagotomy; and after the glossopharyngeal nerves were cut near the base of the skull. The respiratory reflex after injection of xylocaine, 15 minutes after vagotomy, and after cutting the glossopharyngeal nerves was as pronounced as in the intact state, and consisted of an increase in frequency almost totally due to a reduction in tE. With injections given up to 3 minutes after bilateral vagotomy the respiratory response was greatly attenuated and variable. We suggest this question of timing may contribute to the differences seen by different groups of workers. It is clear that intravenous injection of P.D.G. is not an adequate test of J receptor presence in the rabbit.Item Some aspects of the vagal innervation of the canine esophagus : an anatomical study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Animal Science at Massey University(Massey University, 1974) Watson, Alastair GordonThe anatomical disposition of the branches from the vagus nerves to the entire canine esophagus were investigated and the effects of various nerve transections on esophageal function were observed radiographically. Twenty one adult mongrel dogs were carefully dissected; fourteen were dissected as fresh specimens and seven were formalin embalmed and dissected later. Ten of these dogs hed previously undergone various surgical nerve transections: bilateral pharyngoesophageal neurectomy, bilateral cranial thoracic vagotomy, transection of recurrent laryngeal nerves at their origins, double bilateral cranial thoracic vagotomy, and caudal thoracic vagotomies. The surgical approaches for transection of these esophageal nerves have been investigated and the various techniques are described. Esophageal function before and after nerve transection was studied radiographically, especially by cineradiography; all radiographs were made on conscious dogs, trained to stand in a normal position freely eating barium impregnated meal from a bowl placed immediately in front of their forepaws. Radiographic observations on esophageal motility were made on fifteen additional apparently normal dogs. Contrary to standard texts, it was found in the present study that each parent recurrent laryngeal nerve was always divided into two trunks: the recurrent laryngeal nerve proper which coursed directly to and terminated in the ipsilateral intrinsic laryngeal muscles (excluding cricothyroideus), and a more dorsally lying pararecurrent laryngeal nerve which coursed parallel to the recurrent proper but freely supplied many branches to the esophagus and trachea. These esophageal branches were especially numerous on the left side, as the left pararecurrent nerve richly supplied the cranial thoracic esophagus as well as the cervical portion. However, the right pararecurrent nerve supplied the cervical esophagus only. Each pararecurrent nerve then terminated in the anastomotic ramus from the internal branch of the ipsilateral cranial laryngeal nerve. From the experimental studies it was concluded that the recurrent laryngeal nerves were functionally involved with the cranial thoracic esophagus, since this region was completely paralysed following bilateral recurrent laryngeal neureetomy. Some dysfunction was also seen in the cervical esophagus after this operation. The cervical esophagus was primarily innervated and functionally controlled by the pair of pharyngoesophageal nerves which arose solely from the pharyngeal branch of each vagus nerve. Caudal to the origins of the recurrent nerves, the thoracic and abdominal vagi supplied and controlled the caudal thoracic and abdominal portions of the esophagus. The vagus nerves innervate and are involved in the normal function of the gastroesophageal junction, since bilateral cranial thoracic vagotomy considerably altered the activity of this region. However, double caudal thoracic vagotomy appeared only slightly to affect the function of the gastroesophageal junction. In addition, the course and the histological structure of the canine esophagus has been observed and described. During this study, radiographic observations were repeatedly made, on apparently normal dogs, that put in question the validity of the currently held concepts of esophageal physiology. Propulsive esophageal contraction waves did not necessarily directly follow each oropharyngeal deglutition sequence. Swallowed boluses were frequently delayed in the cranial cervical, thoracic inlet, and cranial thoracic regions of the esophagus, Twenty two of the twenty five apparently normal dogs examined, exhibited significant reflux of material from the stomach into the caudal thoracic esophagus. More detailed radiographic studies of the normal canine esophagus under truly physiological conditions are required.