Mary C. Saunders

Innervation of the posterior fossa dura of the cat

This study was designed to identify the location of neurons giving rise to fibers innervating the posterior fossa dura in the cat using horseradish peroxidase (HRP, Sigma, Type VI). Investigations since the 19th century have implicated innervation by cranial nerves V, VII, IX, X and XII and the upper cervical nerves, C1-3. The meninges of the posterior fossa of 14 cats was exposed using one of three surgical approaches: (1) a suboccipital craniectomy and C1 laminectomy, (2) a parieto-occipital craniectomy with removal of the occipital lobe and bony tentorium exposing the meninges over the cerebellum, or (3) an anterior approach through the upper neck, exposing the dura of the ventral surface of the caudal brainstem. A unilateral, curvilinear incision was made in the dura and HRP was applied to the exposed dural edges. Following 48 hours the animals were sacrificed and fixed by perfusion. Cranial nerve ganglia of V, VII, IX, X, dorsal root ganglia (DRG) of C1-3, and superior cervical ganglia (SCG) were removed bilaterally, sectioned and processed with tetramethylbenzidine (TMB). HRP labeled cells were located bilaterally, always more ipsilaterally, in DRG of C1, C2, C3, and SCG with application of HRP to all three regions of the dura. Labeled cells were also located in trigeminal ganglia and superior ganglia of CN X, occasionally bilaterally, depending on the site of application. No HRP was ever identified in neurons of the geniculate ganglion, inferior ganglion of CN X or superior or inferior ganglia of CN IX. This information is valuable to an understanding of the innervation of intracranial structures and the problems of head pain.

Origin of fibers innervating the basilar artery of the cat.

The afferent and efferent projections of the cat basilar artery were examined using retrograde axoplasmic transport techniques. Following application of horseradish peroxidase (HRP) or wheat germ agglutinin-HRP (WGA-HRP) to the vessel wall, retrogradely labeled cells were observed in trigeminal, superior vagal, superior cervical, stellate and pterygopalatine ganglia. WGA-HRP injected into the pterygopalatine ganglion was retrogradely transported to cells of the reticular formation previously described as the superior salivatory nucleus. These results are discussed in relation to recent physiological data demonstrating neural involvement in the control of cerebral blood flow and vascular headache.

Survival of Autologous Fat Grafts in Humans and in Mice

Autologous fat grafts have been used in a number of surgical procedures, yet properties of fat as a transplant material have remained unclear. This study was designed to compare experimental observations of subcutaneous fat grafts in mice with clinical observations of autologous fat grafts placed over the dura following laminectomy in humans. Subcutaneous fat grafts were observed daily in 75 CFl mice with the use of modified Algire back chambers. Grafts were examined histologically and histochemically at intervals up to 60 days after transplantation. Gross and microscopic observations suggest that fat grafts went through a period of initial breakdown of fat cells which was followed by revascularization. This resulted in normal appearing fat, although a smaller volume than the original graft. Three samples of autologous fat grafts from humans were removed during reoperation in the lumbar region up to 22 months after the original procedure. Histological examination revealed revascularized grafts reduced in size: the fat was normal and never replaced by scar tissue.

Identification of motoneurons innervating the tensor tympani and tensor veli palatini muscles in the cat

The somatotopic arrangement of the motoneurons associated with the two non-masticatory muscles innervated by the trigeminal motor nerve, tensor tympani (TT) and tensor veli palatini (TVP), was determined in the cat using retrograde transport of horseradish peroxidase. The motoneurons of the TT are distinct and separate, ventral and ventral-lateral to the rostral two-thirds of the trigeminal motor nucleus. The cells are smaller than those of the motor nucleus and constitute a parvocellular division. Based on functional and morphological criteria, TT motoneurons may be considered as an accessory trigeminal nucleus. The somatotopic arrangement of TVP motoneurons has been described for the first time. These motoneurons are located in the rostral two-thirds of the ventromedial division of the cat trigeminal motor nucleus. The location of motoneurons associated with TT and TVP does not fit the parcellation of the cat trigeminal motor nucleus as described by previous investigators. The motoneurons of these muscles can now be assigned to areas either within (TVP) or adjacent to (TT) the rostral two-thirds of the motor nucleus.

Projections of cervical nerves to the rat medulla

The central course of dorsal root ganglia (DRG) fibers from C1, C2 and C3, and particularly, their brainstem terminations were studied in rats using anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). WGA-HRP was injected into the exposed DRG, and after 3 days the animals were sacrificed and sections of spinal cord and brainstem were processed with tetramethylbenzidine and examined for anterograde transport. Labeled fiber terminals were identified in the dorsal horn and the central cervical nucleus in the spinal cord, and in the intermediate nucleus, cuneate nucleus, external cuneate nucleus and the caudal portion of the nucleus of the solitary tract (NTS) in the brainstem. The projection of primary sensory fibers to the visceral NTS is suggestive of a functional relationship between upper cervical and vagal nerve afferents. The potential association of these nerves with clinical problems of headache and other cephalgias is of interest.

Localization of motoneurons innervating the levator veli palatini muscle in the cat

Recent investigations of the nucleus ambiguus (NA) have attempted to identify motoneurons associated with the branchiomeric muscles of the larynx and pharynx. However, relatively little attention has been directed to the levator veli palatini muscle (LVP) which is critical in respiration, deglutition and eustachian tube function. Although the consensus is that cranial nerve X (vagus) innervates this muscle, some investigators have suggested that the LVP is innervated by either cranial nerve VII (facial) or IX (glossopharyngeal). The present study was designed to identify the specific location of LVP motoneurons within the brainstem. Horseradish peroxidase (HRP) was injected into the LVP of 18 cats. Following a survival period of 24-48 hours, animals were sacrificed and tissue processed according to Mesulams TMB procedure. HRP labeled cells were located in the rostral NA both ipsilateral and contralateral to the side of injection and in the ipsilateral retrofacial nucleus (RFN). There were no labeled cells in the facial nucleus. Innervation of the LVP by cranial nerve VII would thus be excluded. This is the first report to definitively localize LVP motoneurons. Although the innervation of LVP by cranial nerve X is generally agreed upon in basic anatomy textbooks, identification of LVP motoneurons within the NA does not exclude innervation by cranial nerve IX.

Localization of motoneurons innervating the stylopharyngeus muscle in the cat

Recent investigations of the nucleus ambiguus (NA) have attempted to identify motoneurons associated with muscles of the larynx and pharynx. However, relatively little attention has been directed to the stylopharyngeus muscle, which is important in elevation of the pharynx in swallowing and speech. The present study was designed to identify the specific location of stylopharyngeus motoneurons within the brainstem. Horseradish peroxidase or fluorescent dye was injected into the stylopharyngeus muscle of 12 cats. Retrogradely labeled cells were located ipsilateral in the rostral NA and retrofacial nucleus. This is the first report to definitively localize stylopharyngeus motoneurons.

Central brainstem projections of the superior vagal ganglion of the cat

The central projections of the cat superior vagal (jugular) ganglion (SVG) cells were determined using anterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). WGA-HRP was injected into the SVG of 5 cats, 3 of which had the vagal nerve sectioned distal to the jugular ganglion several days previously. Following 72 h, the animals were sacrificed and the brainstem and rostral cervical spinal cord sectioned and processed with tetramethylbenzidine (TMB) and examined for anterograde transport. The vagal root afferent fibers entered the brainstem at the level of the caudal facial motor nucleus and bifurcated into descending tracts. Terminal label was identified in: the dorsal lateral subnucleus of the nucleus tractus solitarius (NTS); nucleus interpolaris and nucleus caudalis of spinal V; the ventrolateral aspect of the cuneate nucleus and; the superficial laminae (I, II) of the rostral C1-dorsal horn. To our knowledge this is the first report describing central vagal afferent terminations following injection of current axonal tract tracing substances into the isolated superior vagal ganglion. The projection of jugular ganglion cells to a region of the NTS associated with cardiovascular function is of particular interest, and may be related to ganglion cells known to innervate the cerebral vasculature and meninges.