[Morphological features of the rat stellate ganglion during early postnatal development]

The aim of this work was to study the anatomical characteristics of the stellate ganglion (SG) and the morphometric characteristics of its neurons in rats of different age groups (newborn, 10-, 20-, 30-, 60- and 180-day-old) using anatomical and histological methods. The results obtained indicated that in rats since birth there were three variants of branch origin from the medial margin of SG. No differences were observed in these variants between right and left SG. The sizes of both SG and its neurons increased during the first two months of postnatal development. The density of neurons in SG sections decreased from the moment of birth until the six months of age. The number of SG neurons did not change significantly in the postnatal ontogenesis. Thus, SG in rats is anatomically formed by the moment of birth, while the sizes and morphometric characteristics of SG neurons become finally stabilized by the second month of age.

Serial stellate ganglion blocks for intractable postherpetic itching in a pediatric patient: a case report

BACKGROUND

While intractable itching may be rarely associated with postherpetic neuralgia, it can have catastrophic complications if present.

METHOD

We highlight a severe case of postherpetic itching in a 10-year-old male with Fanconi's and aplastic anemia, refractory to conventional treatments and requiring intravenous sedation.

RESULTS

Our use of 3 sequential stellate ganglion blocks with 5.5 mL of 0.25% bupivacaine provided significant improvement of the symptoms for 4 months after the last procedure.

CONCLUSION

Although further evaluation is needed, we feel that novel use of sympathetic blockade may provide treatment for intractable itching. Highlighted is the possible influence of the sympathetic system in the pathophysiology of postherpetic itch.

IMPLICATION

The use of serial stellate ganglion blocks may be a treatment option for patients with intractable itching and postherpertic neuralgia of the neck and arm region. This technique may lead to more permanent solutions such as pulse radiofrequency lesion or chemical neurolysis of sympathetic ganglions for postherpetic itch.

Ultrasound-guided stellate ganglion block successfully prevented esophageal puncture

Stellate ganglion block is utilized in the diagnosis and management of various vascular disorders and sympathetically mediated pain in the upper extremity, head and neck. The cervical sympathetic chain is composed of superior, middle, intermediate, and inferior cervical ganglia. However, in approximately 80% of the population, the inferior cervical ganglion is fused with the first thoracic ganglion, forming the stellate ganglion also known as cervicothoracic ganglion. The stellate ganglion lies medial to the scalene muscles, lateral to the longus coli muscle, esophagus and trachea along with the recurrent laryngeal nerve, anterior to the transverse processes and prevertebral fascia, superior to the subclavian artery and the posterior aspect of the plura, and posterior to the vertebral vessels at C7 level. Consequently, inadvertent placement of the needle into the vertebral artery, thyroid, neural tissues, or esophagus can occur with the fluoroscopic or blind approach. While fluoroscopy is a reliable method for identifying boney structures, ultrasound may identify the vertebral vessels, thyroid gland and vessels, longus coli muscles, nerve roots and the esophagus. Thus, ultrasound may prevent inadvertent placement of the needle into these structures as might happen with either the blind technique or fluoroscopic technique. A patient with complex regional pain syndrome type I of the left upper extremity was scheduled for left stellate ganglion block with the anterior paratracheal approach under fluoroscopy. Real-time ultrasound imaging prevented inadvertent injury to the esophagus as well as the thyroid gland and vessels. Ultrasound-guided block may improve patient safety by avoiding the soft tissue structures in the needle path that can't be readily seen by fluoroscopy. This may be particularly useful in the patient with asymptomatic pharyngoesophageal diverticulum (Zenker diverticulum).

Comparison of different injectate volumes for stellate ganglion block: an anatomic and radiologic study

BACKGROUND

Volumes from 5 to 20 mL of local anesthetic are used for stellate ganglion block. The variation of practice gave us the impetus to investigate the distribution of 3 different volumes of solution. We documented the regions reached by each volume to assess the possibility to reduce the injectate to 5 mL.

MATERIALS AND METHOD

A total of 42 cadavers (84 halves), fixed by Thiel's method and on which pulse simulation was performed, were investigated. Of these 84 halves, 28 were injected with 5 mL of contrast (group A), 28 halves with 10 mL (group B), and 28 halves with 20 mL (group C), according to the tissue-displacement method. Immediately after injection, the cadavers were investigated by use of CT scans with a possible 3-dimensional reconstruction. In addition, 4 halves of group A and group B were dissected, and the contrast distribution was determined by photography.

RESULTS

Group A showed a constant dissemination from C4 to Th2-Th3, without spreading to ventral or lateral regions. In group B, a persistent spread from C4 to Th3 was documented. Ventral and lateral regions were also reached in one third of the specimens. Group C showed a constant dissemination from C3 to Th4-Th5, with additional spread to ventral, lateral, and posterior regions of the neck similar to that in group B.

CONCLUSION

The use of 5 mL results in an almost ideal vertical distribution in most of the cadavers, whereas high volumes--20 mL more so than 10 mL--are at risk of spreading extensively in both the vertical direction and also uncontrollably to other regions of the neck.

Gross anatomical study of the sympathetic cardiac nerves in the house musk shrew (Suncus murinus)

The sympathetic cardiac nerves originating from the cervical and upper thoracic sympathetic ganglia in the house musk shrew (Suncus murinus) were examined using macroscopic and whole-mount immunohistochemical methods. Based on the results, the nerves were macroscopically classified into the following three groups: nerves innervating the cervical sympathetic ganglia mainly to the arterial porta of the heart; nerves supplying the stellate and thoracic sympathetic ganglia at the level of T2-T5 or T6 for both the arterial and venous portae of the heart; and nerves innervating the thoracic sympathetic ganglia at the level of T4-T9 to the esophagus and lung and then the heart via the blood vessels within the mediastinal pleura. These findings in the house musk shrew suggest a possible primitive morphological pattern of the cervical and thoracic sympathetic nervous system that may be related to those in other mammals, including humans.

The vertebral nerve revisited

There is significant paucity in the literature regarding the vertebral nerve. Moreover, descriptions of this structure are conflicting. To evaluate further the anatomy and potential clinical significance of this structure, 10 fresh adult cadavers (20 sides) underwent dissection and macroscopic observation of this structure. All specimens were found to have a vertebral nerve that originated from the stellate ganglion with the exception of two left sides (10%) in which this nerve arose from the inferior cervical ganglion. This nerve ascended posteromedial to the vertebral artery. The vertebral nerve was found to be, in essence, a long and deep gray ramus communicans that connected most commonly the stellate ganglia to C6 or C7 spinal nerves by passing through the C6 and C7 transverse foramina. Fifteen percent of sides were found to have a vertebral nerve that was plexiform in its configuration. Fifty percent were found to have very small branches that entered the fibrous capsule of adjacent zygapophyseal and intervertebral joints. Some specimens were noted to have meningeal branches of the vertebral nerve. Based on our observations, the vertebral nerve is simply a deep ramus communicans, which often provides articular and meningeal branches to the adjacent spine. As neck pain is a significant reason for physician office visits, additional knowledge of the nerves innervating the joints and adjacent meninges of the neck could be important for both surgical and medical blockade of nerve fibers.

[Rhythmical electrical activity in the cat stellate ganglion during postnatal ontogenesis]

Electrical activity of the stellate ganglion was studied in newborn, 10-, 20-, 30-day-old, two- and six-month-old kittens using the spectral analysis. The development of sympathetic activity patterns was different during ontogenesis. The amplitude of discharges increased from the period of birth until the second month of kittens' life. In newborn and 10-day-old kittens, synchronous discharges of postganglionic fibers were represented by slow and low frequency impulses with frequencies of breathing and heart rate. ppears in 20-day-old kittens. The formation of the sympathetic discharge patterns ends at the second month of animals life.

Cervico-thoracic ganglion: Its clinical implications

Lesions of the cervicothoracic ganglion (CTG) result in interruption of sympathetic fibers to the head, neck, upper limb, and thoracic viscera. The accurate understanding of the anatomy of the CTG is relevant to sympathectomy procedures that may be prescribed in cases where conventional intervention has failed. This study documents the incidence and distribution of the CTG to avoid potential complications such as Horner's syndrome and cardiac arrhythmias. This study utilized 48 cadavers, in which a total of 89 sympathetic chains were dissected. The inferior cervical ganglion (ICG) and the first thoracic ganglion was fused in 75 cases (84.3%) to form the CTG. It was present bilaterally in 48 of these specimens (65.3%). Three different shapes of CTG were differentiated, viz. spindle, dumbbell, and an inverted "L" shape. The dumbbell and inverted "L" shapes demonstrated a definite "waist" (i.e., a macroscopically visible union of the ICG and T1 components of the CTG). Rami from the CTG was distributed to the brachial plexus, the subclavian and vertebral arteries, the brachiocephalic trunk, and the cardiac plexus. This study demonstrates a high incidence of a double cardiac sympathetic nerve arising from CTG. It is therefore imperative that in the technique of sympathectomy, for intractable anginal pain, the surgeon excises both these rami but does not destroy the ganglion itself. The ever-improving technology in endoscopic surgery has made investigations into the nuances of the anatomy of the sympathetic chain essential.

Anatomical variations of the second thoracic ganglion

In recent years the second thoracic ganglion has gained anatomical significance as an important conduit for sympathetic innervation of the upper extremity. Thoracoscopic excision of the second thoracic ganglion is now widely recognized as affording the most effective treatment option for palmar hyperhidrosis. This study recorded the incidence, location and associated additional neural connections of the second thoracic ganglion. Bilateral dissection of 20 adult cadavers was undertaken, and all neural connections of the second thoracic ganglion were recorded. Nineteen cadavers (95%) demonstrated additional neural connections between the first thoracic ventral ramus and second intercostal nerve. These were classified as either type A (47.5%) or type B (45%) using the intrathoracic ramus (nerve of Kuntz) between the second intercostal nerve and the ventral ramus of the first thoracic nerve as a basis on both right and left sides. The second thoracic ganglion was commonly located (92.5%) in the second intercostal space at the level of the intervertebral disc between the second and third thoracic vertebrae. Fused ganglia between the second thoracic and first thoracic (5%) and stellate (5%) ganglia were noted. These findings should assist the operating surgeon with a clear knowledge of the anatomy of the second thoracic ganglion during thoracoscopic sympathectomy with a view to improving the success rate for upper limb sympathectomy.

[A new method of performance of thoracic sympathectomy, based on the analysis of peculiarities of anatomical architecture of cervicothoracic sympathetic stem]

Peculiarities of anatomic structure (disposition, form, size) of stellate ganglion, II and III thoracic sympathetic ganglions together with their branches were suggested. There were established their morphological differences. Peculiarities of anatomical structure of the "lateral branch" II sympathetic ganglions were studied, its role in occurrence of the disease recurrence after performance of the thoracic sympathectomy performance was proved. Basing on the results achieved the method of thoracoscopic sympathectomy performance for Raynaud's phenomenon was elaborated.

[Neural circuit of the cervical sympathetic nervous system with special reference to input and output of the cervical sympathetic ganglia: relationship between spinal cord and cervical sympathetic ganglia and that between cervical sympathetic ganglia and their target organs]

Using anterograde labeling technique with Phaseolus vulgaris leucoagglutinin (PHA-L), we demonstrated the arborization pattern of a single preganglionic axon in the superior cervical ganglion (SCG) and stellate ganglion (STG). These axons expanded in the longitudinal direction, but not for transverse direction. Segmental relationship was identified between the spinal cord and STG, as seen between spinal cord and sympathetic ganglia in the thoraco-lumbar region, but we did not find any segmental relationship between the spinal cord and SCG. Some sympathetic preganglionic neurons in the lateral horn of the thoracic cord, especially in the intermediolateral nucleus (IML) have nitric oxide synthase (NOS) activity. We demonstrated that SCG neurons, which were heavily innervated by these NOS-positive neurons, tended to innervate organs that have some secretory functional tissues. Finally, we showed that the size of neuronal somata does not correlate with the size of target organs, as has been reported in previous studies. We should consider that there are other factors determining the size of neuronal somata, such as the size of dendritic field or volumes of NGF secretory from target tissues.

Circuits and projections of cat stellate ganglion

BACKGROUND

Although connections of stellate ganglion (SG) have been widely explored, some features of pathways and projections remain unknown, such as the source and fate of preganglionic axons present in output branches, including both synaptically interrupted and traversing pathways as well as axon composition (efferent and afferent) of these output nerves.

METHODS

Circuits and central projections of cat SG were investigated using horseradish peroxidase (HRP) tracer and electrophysiologic techniques including stimulation of ganglionic branches during recording of genesis of compound action potentials in other nerves or centrally evoked responses.

RESULTS

All branches of SG including vertebral nerve are mixed, i.e., they contain axons that synapse in the periphery or traverse ganglia. A novel synaptically interrupted pathway bi-directionally coursing along subclavian branches and inferior cardiac nerve was identified. Preganglionic axons traversing stellate ganglion course in communicating branch to vagus nerve and to inferior cardiac nerve, a small number of these preganglionic axons traversing stellate ganglion reach cervical sympathetic trunk via subclavian branches. For the first time, a small number of preganglionic traversing pathways were also detected in vertebral nerve. Afferent axons with somata located in C8-T7 dorsal root ganglia, identified in all branches of SG, projected centrally to neurons in thalamus and somatosensory zones of cerebral cortex and coincided with afferent projections of brachial plexus.

CONCLUSIONS

Present data contribute to the morphologic description of autonomic regulation of thoracic organs, including centrally independent peripheral autonomic axon reflexes.

Thoracic origin of a sympathetic supply to the upper limb: the 'nerve of Kuntz' revisited

An understanding of the origin of the sympathetic innervation of the upper limb is important in surgical sympathectomy procedures. An inconstant intrathoracic ramus which joined the 2nd intercostal nerve to the ventral ramus of the 1st thoracic nerve, proximal to the point where the latter gave a large branch to the brachial plexus, has become known as the 'nerve of Kuntz' (Kuntz, 1927). Subsequently a variety of sympathetic interneuronal connections down to the 5th intercostal space were reported and also described as the nerve of Kuntz. The aim of this study was to determine: (1) the incidence, location and course of the nerve of Kuntz; (2) the relationship of the nerve of Kuntz to the 2nd thoracic ganglion; (3) the variations of the nerve of Kuntz in the absence of a stellate ganglion; (4) to compare the original intrathoracic ramus with sympathetic variations at other intercostal levels; and (5) to devise an appropriate anatomical classification of the nerves of Kuntz. Bilateral microdissection of the sympathetic chain and somatic nerves of the upper 5 intercostal spaces was undertaken in 32 fetuses (gestational age, 18 wk to full term) and 18 adult cadavers. The total sample size comprised 99 sides. Sympathetic contributions to the first thoracic nerve were found in 60 of 99 sides (left 32, right 28). Of these, 46 were confined to the 1st intercostal space only. The nerve of Kuntz (the original intrathoracic ramus) of the 1st intercostal space had a demonstrable sympathetic connection in 34 cases, and an absence of macroscopic sympathetic connections in 12. In the remaining intercostal spaces, intrathoracic rami uniting intercostal nerves were not observed. Additional sympathetic contributions (exclusive of rami communicantes) were noted between ganglia, interganglionic segments and intercostal nerves as additional rami communicantes. The eponym nerve of Kuntz should be restricted to descriptions of the intrathoracic ramus of the 1st intercostal space. Any of these variant sympathetic pathways may be responsible for the recurrence of symptoms after sympathectomy surgery.

Sympathetic blockade for the relief of chronic pain

The sympathetic blocks are useful in many ways for relief of chronic pain. The sympathetic block can be caused at pre- and paravertebral sympathetic ganglia eg, stellate ganglia, coeliac plexus and lumbar sympathetic ganglia. Indications for sympathetic blockade are: Complex regional pain syndrome, phantom limb pain, central pain, acute pancreatitis, pancreatic cancer and cancer pain from upper abdominal viscera. Stellate ganglion blockade is required for the diagnosis, prognosis and therapy for painful and other conditions associated with sympathetic dysfunctions of head, neck and upper extremity. Coeliac plexus block is indicated in pain due to intra-abdominal cancer, stemming from organs innervated by coeliac plexus. Lumbar sympathetic block is indicated for diagnosis, prognosis and therapy for painful and other conditions associated with sympathetic dysfunctions like complex regional pain syndrome I and II, herpes zoster, amputation stump pain and inoperable peripheral vascular vasospastic diseases of the lower limb. Indications for superior hypogastric block are the prognostic and therapeutic purposes of cancer pelvic organs--uterus, cervix, bladder, prostate, urethra, testes and ovaries.

[Innervation centers in the cervical and thoracic trachea]

Using HRP axonal transport links between trachea and ganglia of cervical thoracic regions of right and left sympathetic trunks, spinal ganglia and vagal posterior ganglia were established. Quantitative and morphometric characteristics of neurocytes of contralateral ganglia involved into trachea innervation were given. Peculiarities of localization of innervation centres of cervical and thoracic trachea regions were established.

Anatomically and physiologically based guidelines for use of the sphenopalatine ganglion block versus the stellate ganglion block to reduce atypical facial pain

This literature review is designed to develop guidelines needed for the use of a sphenopalatine ganglion block versus a stellate ganglion block to reduce atypical facial pain. We have reviewed the basic anatomy of both ganglia and the physiological responses usually associated with each, and have given an opinion on appropriate use of these therapeutic modalities.

Morphological features of neurons innervating different viscera in the cat stellate ganglion in postnatal ontogenesis

Retrograde axonal transport of horseradish peroxidase (HRP) was used in this study to determine morphological parameters in the stellate ganglion (SG) in newborn, 10-, 20-day- and 1-month-old kittens. Neurons with the largest average size participated in innervation of the heart in newborn kittens and in innervation of the sternocleidomastoid muscle in other animals. The number of neurons sending their axons to target-organs also changed in postnatal ontogenesis. Regardless of the site of HRP injection at animals of all ages labeled neurons in the SG were located in certain zones on a topographical basis. Thus, it is concluded that in postnatal ontogenesis the neuronal organization of the SG changes in parallel to the increase of neuronal sizes and ganglion cross section area and practically finishes at 1 month of age.

Organization of the sympathetic innervation of the forelimb resistance vessels in the cat

Detailed information on the outflow pathway of sympathetic vasoconstrictor fibers to the upper extremity is lacking. We studied the organization of the sympathetic innervation of the forelimb resistance vessels and of the sinoatrial (SA) node in the decerebrated, artificially respirated cat. The distal portion of sectioned individual rami T1-8 and the sympathetic chain immediately caudal to T8 on the right side were electrically stimulated while the right forelimb perfusion pressure (forelimb perfused at constant flow) and heart rate were recorded. Increases in perfusion pressure were evoked by stimulation of T2-8 (maximal response T7: 55 +/- 2.3 mm Hg). Responses were still evoked by stimulation of the sympathetic chain immediately caudal to T8 (44 +/- 15 mm Hg). Increases in heart rate were evoked by the stimulation of more rostral rami (T1-5; maximal response T3: 55.2 +/- 8 bpm). These vasoconstrictor and cardioacceleratory responses were blocked by the cholinergic antagonists hexamethonium and scopolamine. Sectioning of the vertebral nerve and the T1 ramus abolished the vasoconstrictor response. Stimulation of the vertebral nerve and of the proximal portion of the sectioned T1 ramus increased perfusion pressure (69 +/- 9 and 34 +/- 14 mm Hg, respectively), which was unaffected by ganglionic cholinergic block. These data suggest that forelimb resistance vessel control is subserved by sympathetic preganglionic neurons located mainly in the middle to caudal thoracic spinal segments. Some of the postganglionic axons subserving vasomotor function course through the T1 ramus, in addition to the vertebral nerve.

IMPLICATIONS

Forelimb vasculature is controlled by sympathetic preganglionic neurons located in middle to caudal thoracic spinal segments and by postganglionic axons carried in the T1 ramus and vertebral nerve. This helps to provide the anatomical substrate of interruption of sympathetic outflow to the upper extremity produced by major conduction anesthesia of the stellate ganglion or spinal cord.

The brachial plexus in the chacma baboon (Papio ursinus)

The brachial plexus in each of ten embalmed, mature chacma baboons was dissected to document the structure and branching pattern of this nerve plexus in this increasingly used research animal. In general, the brachial plexus in the chacma baboon was similar to the plexuses in the vervet and other Old World monkeys. However, several aspects were comparable to those observed in domestic animals. Thus the bipedal and quadrupedal abilities of the chacma baboon were reflected in the structure of its brachial plexus.

Neurons lying in the white matter of the upper cervical spinal cord project to the intermediolateral cell column

Neurons lying in the white matter of the upper cervical spinal cord become transneuronally labelled following pseudorabies virus injections into the kidney or stellate ganglion, suggesting that they project directly to sympathetic preganglionic neurons. In the present study, we extend these findings and report here that i) neurons in both the lateral spinal nucleus and lateral funiculus become transneuronally labelled after pseudorabies virus injections into the superior cervical ganglion, stellate ganglion, celiac ganglion, or adrenal gland and ii) both of these two cell groups project directly to the sympathetic preganglionic neurons as demonstrated with the Phaseolus vulgaris leuco-agglutinin axonal tracing method. In addition, lateral funiculus neurons project to the cervical and upper thoracic dorsal horn (lamina V), intermediate gray matter (laminae VII and X), and ventral horn. The lateral spinal nucleus also projects to the medial part of laminae I and II, V, VII. To verify that pseudorabies virus-infected lateral funiculus and lateral spinal nucleus cells have a neuronal phenotype, we demonstrated that these cells also can be immunostained with antibodies directed against a neuron specific marker, neuronal nuclear protein called NeuN, but not with antibodies against glial acidic fibrillary protein or oligodendroglia. In summary, this report provides the first evidence that two descending sympathetic projection systems arise from neurons lying within the white matter of the cervical spinal cord.

Cardiac neurones of autonomic ganglia

The properties of the postganglionic sympathetic neurones supplying the heart and arising in the stellate and adjacent paravertebral ganglia of various species are discussed with respect to their location, morphology, synaptic input and membrane characteristics. Results from our laboratory on the morphology of rat stellate neurones projecting to the heart were obtained either by intracellular injection of hexammine cobaltic (III) chloride or by retrograde labelling of cells using cobalt-lysine complex. Intracellular recordings were made from cells using electrodes filled either with potassium chloride plus hexammine cobaltic chloride or potassium acetate. Neurones which projected axons into cardiac nerve branches arising from the stellate ganglion were termed putative cardiac neurones, because of the possibility that some supply pulmonary targets. Putative cardiac neurones had unbranched axons and were ovoid or polygonal in shape, but showed considerable variation in soma size and in the complexity of dendritic trees. The mean two-dimensional surface area was 463 microns2 and the mean number of primary dendrites was seven. Other studies have found that the morphology of rat stellate ganglion neurones is similar to that of superior cervical ganglion cells. However, in strains of rat displaying spontaneous hypertension, dendritic length may be increased. Histochemical studies do not, as yet, seem to have demonstrated a distinctive neurochemical profile for stellate cardiac neurones, but various types of peptide-containing intraganglionic nerve fibres have been identified in the guinea pig. In our electrophysiological studies, putative cardiac neurones were found to receive a complex presynaptic input arising from the caudal sympathetic trunk and from T1 and T2 thoracic rami. In addition, 16% of cardiac neurones received a synaptic input from the cardiac nerve. The properties of postganglionic parasympathetic neurones distributed in the cardiac plexus and termed intrinsic cardiac neurones are discussed, including the results of studies on cultures of these neurones.

Retroesophageal right subclavian artery originating from the aortic arch distal and dorsal to the left subclavian artery

In the cadaver of a Japanese 79 year-old man a retroesophageal right subclavian artery was observed to be derived from the arch of the aorta slightly distal and dorsal to the left subclavian artery. Its origin formed Kommerell's arterial diverticulum (50 mm in circumference), and it passed between the esophagus and the vertebral column and continued to the right to become the axillary artery. No right recurrent laryngeal nerve was observed. There was a right ansa subclavia around the subclavian artery. Although this anomaly is relatively rare, it is important as a cause of dysphagia lusoria.

Transneuronal labeling of CNS neuropeptide and monoamine neurons after pseudorabies virus injections into the stellate ganglion

The viral transneuronal labeling method was used in combination with immunohistochemical procedures to identify CNS neuropeptide and monoamine neurons that innervate the sympathetic preganglionic neurons (SPNs) which project to the stellate ganglion--the principal source of the sympathetic supply to the heart. Transneuronal labeling was found at three CNS levels: spinal cord, brainstem, and hypothalamus. In the thoracic spinal cord, apart from the pseudorabies virus (PRV)-labeled stellate SPNs, PRV-labeled neurons were localized in laminae I/II, IV, V, VII, and X as well as in the lateral spinal nucleus and lateral funiculus. In the C1-C4 spinal segments, labeled neurons were found in the lateral funiculus as well as laminae V and VII of the spinal gray matter. PRV-labeled cells were identified in lamina V and the dorsolateral funiculus of the lumbar spinal cord. Three medullary areas were consistently labeled: rostral ventromedial medulla (RVMM), rostral ventrolateral medulla (RVLM), and caudal raphe nuclei. The greatest concentration of labeling was found in the RVMM. This projection arose from adrenergic, serotonergic (5-HT), thyrotropin releasing hormone (TRH), substance P, somatostatin, enkephalin, and vasoactive intestinal peptide (VIP) immunoreactive neurons. The RVLM projection originated mainly from C1 adrenergic neurons, some of which contained immunoreactive neuropeptide Y (NPY). C3 adrenergic-NPY neurons lying near the floor of the 4th ventricle were also labeled. Enkephalin-, somatostatin- and VIP-immunoreactive RVLM neurons also contributed to this projection. 5-HT neurons of the caudal raphe nuclei (raphe pallidus, raphe obscurus, and raphe magnus) were labeled; some of these contained substance P or TRH-immunoreactivity with an occasional neuron staining for all three putative neurotransmitters. In the pons, catecholamine neurons in the A5 cell group, subcoeruleus and Kolliker-Fuse nuclei were labeled. The midbrain contained relatively few infected cells, but some were present in the Edinger-Westphal and precommissural nuclei. Forebrain labeling was concentrated in the paraventricular hypothalamic nucleus (PVN) with lesser amounts in the lateral hypothalamic area (LHA) and the perifornical region. In the PVN, oxytocin-immunoreactive neurons accounted for the greatest chemically-defined projection while corticotrophin releasing factor (CRF), vasopressin-, and angiotensin II-immunoreactive neurons provided successively lesser inputs. In the LHA, angiotensin II-immunoreactive neurons were labeled. In summary, this study provides the first detailed map of the chemically-coded CNS neurons involved in the control of the cardiosympathetic outflow.

Distribution and origin of the peripheral innervation of rat cervical esophagus

Several neurotransmitters, neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), galanin, enkephalin, calcitonin-gene related peptide (GGRP), substance P, as well as nitric oxide synthase (NOS), and the noradrenergic marker tyrosine-hydroxylase (TH) were localized by immunocytochemistry in the cervical esophagus of rat. Nerve fibers containing the neuropeptides, NOS, and TH were distributed in the myenteric plexus, around muscle bundles and small blood vessels. Injection of the retrograde tracer True Blue (TB) into the cervical esophagus resulted in the appearance of labeled nerve cell bodies in the superior cervical, the stellate, the nodose, the sphenopalatine, the dorsal root ganglia at levels C2-C7, and in local ganglia close to the thyroid. Most of the TB-labeled nerve cell bodies in the superior cervical ganglia contained NPY. In the stellate ganglion, a few labeled nerve cell bodies contained VIP whereas an additional few cell bodies stored VIP. In local ganglia, the majority of labeled cell bodies contained VIP. In the nodose ganglion and cervical dorsal root ganglia, the majority of the labeled nerve cell bodies stored CGRP. The results indicate that the cervical esophagus has a dense innervation with multiple neurotransmitters emanating from several ganglia. As judged by the pattern of nerve fiber distribution, they may regulate esophageal peristalsis and blood flow, some of them possibly in a cooperative manner.

Determination of the origin of autonomic nerves of the tongue using horseradish peroxidase as tracer

Autonomic innervation of the tongue was investigated in cats using the horseradish peroxidase retrograde tracing method. The tongue was found to be innervated by sympathetic fibers originating in the ipsilateral superior cervical ganglion, but not by those originating in the middle cervical ganglion or stellate ganglion. The tongue was also innervated by fibers originating in the ipsilateral pterygopalatine ganglion, suggesting that this innervation is parasympathetic.

Distribution of neuropeptides in the porcine stellate ganglion

The localization and distribution of neuropeptides including neuropeptide Y (NPY), [Met5]enkephalin-Arg6-Gly7-Leu8 (MEAGL), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), substance P and somatostatin (SOM) were analyzed in the stellate ganglion of the pig by use of the indirect immunofluorescence technique. NPY, MEAGL, SOM, VIP and CGRP immunoreactivities were found to exist in subpopulations of neuronal cell bodies of the stellate ganglion. A population of the small intensely fluorescent (SIF) cells showed MEAGL immunoreactivity. In addition, the presence of NPY-, MEAGL-, CGRP-, SP-, SOM- and VIP-immunoreactive nerve fibers and axonal varicosities were observed in the stellate ganglion. The localization and pattern of distribution of these peptides in the porcine stellate ganglion were compared with studies carried out on stellate ganglia of other mammalian species.

An investigation into the extrinsic blood supply and the microvasculature of the rat stellate ganglion

The extrinsic supply of the rat stellate ganglion (STG) has been investigated by histological examination of the vasculature following india ink injections by a variety of routes. The main arterial supply to the STG is derived from an un-named branch of the pericardiophrenic branch of the costocervical trunk of the subclavian artery but a small contribution is made to the rostral part of the STG from microvessels running in the cervical sympathetic trunk. Similarly there are microvessels running in the nerve trunks connected to the STG and these, together with those in the cervical sympathetic trunk, can perfuse the STG when the subclavian artery is occluded. The second and third intercostal arteries do not supply the STG. Measurements of alkaline phosphate-stained microvascular endothelial cells reveal that microvessel diameters (6.5 +/- 0.54 microns) in the rat STG are comparable to those in other rat sympathetic ganglia as is the endothelial surface area available for exchange to a given volume of blood. However the density of the microvascular bed in the STG is greater (553.2 mm/mm3) than in other rat sympathetic ganglia and individual neurones in the STG are surrounded by a higher number of microvessels within a radius of 25 microns from the centre of the nucleus. These results suggest that the metabolic demands of STG neurones may be higher than in other sympathetic ganglia.

Immunohistochemical study of the sympathetic and sensory innervation to the blood vessels of the dog forepaw

Immunohistochemical staining of arteries supplying the dog forepaw showed a dense distribution of nerve fibers which were immunoreactive to tyrosine hydroxylase (TH), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), substance P (SP), and calcitonin gene-related peptide (CGRP) around the vascular walls. The density of each immunoreactive fiber tended to increase in the peripheral branch of the vascular tree. Retrograde axonal tracing with Fast Blue from the artery revealed that these immunoreactive fibers originated from NPY-containing catecholaminergic as well as VIP/SP/CGRP-containing non-catecholaminergic neurons in the stellate ganglion and SP/CGRP-containing neurons in the dorsal root ganglia of segments C7 to Th1. After stellate ganglionectomy, TH-, NPY-, and, VIP-immunoreactive fibers disappeared completely from the arterial walls while approximately 40% of SP- and CGRP-immunoreactive fibers remained. The present results indicate that the artery of the dog forepaw receive triple innervation of adrenergic sympathetic, non-adrenergic sympathetic, and sensory fibers, and suggest that about 40% of SP- and CGRP-immunoreactive fibers are of sensory origin.

The spread of solutions during stellate ganglion block

BACKGROUND AND OBJECTIVE

Though cervical paratracheal injections for the purpose of sympathetic block are customarily referred to as stellate ganglion blocks, there is no documentation of the actual site of local anesthetic action. The objective of this study is to test whether solution travels to the stellate ganglion during injections commonly used to anesthetize it.

METHODS

In eight volunteers, magnetic resonance imaging was used to delineate the distribution of 15 ml saline injected by an anterior paratracheal technique at the sixth and seventh cervical vertebral levels.

RESULTS

Injectate was not delivered to the stellate ganglion but rather passed anterior to it.

CONCLUSIONS

The findings suggest that sympathetic neural block during stellate ganglion block may take place at sites other than the stellate ganglion.

MR imaging of the stellate ganglion: normal appearance

The stellate ganglion has not previously been identified by imaging techniques. MR imaging shows the stellate ganglion at the thoracic inlet adjacent to the neck of the first rib, lateral to the longus colli muscle and posterior to the vertebral artery. Although its shape varies somewhat, it can be identified consistently in normal persons.

Anterograde transsynaptic transport of WGA-HRP from spinal afferents to postganglionic sympathetic cells of the stellate ganglion of the guinea pig

After injection of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) or choleragenoid conjugated HRP (B-HRP) into lower cervical and upper thoracic dorsal root ganglia (DRG), HRP reaction product was observed in peripheral fibers of spinal afferents and in postganglionic cell bodies of the stellate ganglion (SG) in the guinea pig. After WGA-HRP injection into C8-T3 or T5 DRG, HRP-labelled cells were observed to cluster at the rami within the SG, with peak labelling observed 36 h after injection. SG cell labelling occurred with B-HRP as well, but not with native HRP after injection into thoracic DRG. Injection of this tracer in C8 DRG gave rise to a small number of labelled cells. In contrast to the labelling pattern following thoracic or C8 DRG injections, injection of WGA-HRP or native HRP into C6 DRG, led to random SG cell labelling. We conclude that the anterograde transsynaptic transport, following injection of WGA-HRP into thoracic DRG, provides a method to selectively label a population of postganglionic sympathetic neurons within the SG. A combination of transsynaptic and retrograde transport appears to be responsible for labelling after injection into C8 DRG, whereas labelling after C6 DRG injections seems to be due primarily to retrograde transport.

[Origin and the functional role of adrenergic fibers of the vagus nerve in cats]

Origin of adrenergic fibres of vagus is studied. They are shown to appear in the thoracic vagus through caudal anastomosis introduction. The observations indicated that axons of spinal neurons and neurons of the ganglion stellate passed through caudal anastomosis and entered a thoracic vagus nerve. Stimulation of the thoracic vagus in cats after atropine sulphate injection increases the heart rate.

[Localization of neurons, making projections via the postganglionic nerves of the stellate ganglion]

Distribution of neurons, forming cardiac nerves of the cat stellate ganglion, has been investigated. The inferior cardiac nerve conducts inotropic influences to the heart. It is formed by the neurons localized in the caudal part of the ganglion. The caudal anastomosis conducts chronotropic influences to the heart. It is formed by the neurons localized in the inferior part of the ganglion and the ventral horn of the spinal nucleus and nucleus intercalatus. Axons of the preganglionic neurons pass through the ganglion and are not interrupted.

Stellate ganglion innervation of the vertebro-basilar arterial system demonstrated in the rat with anterograde and retrograde WGA-HRP tracing

Stellate ganglia projections to cerebral arteries have been investigated with wheatgerm-agglutinated horseradish peroxidase (WGA-HRP). Injections of WGA-HRP into the stellate ganglia resulted in labelling of nerve fibres on the vertebral and basilar arteries, and their side branches. The innervation was bilateral, but with an ipsilateral predominance. After WGA-HRP application on the basilar artery, retrogradely labelled cells appeared in both stellate ganglia, but most numerously in the right ganglion (70-75%). Failure to detect stellate projections to cerebral arteries in 6-hydroxydopamine (6-OHDA)-pretreated animals indicates that these fibres are of noradrenergic sympathetic character. It is suggested that the stellate fibres follow the vertebral arteries towards the basilar artery and its branches.

[Pre- and postganglionic pathways conducting central sympathetic chrono- and inotropic effects to the heart of the cat]

In anesthetized cats, the preganglionic input to the stellate ganglion involved Th3 and Th4 white rami. The chronotropic influences to the heart travelled through caudal anastomose whereas inotropic those--through inferior cardiac nerve. Neurons of these nerves are distributed over the ganglion stellate in different sites. The data obtained suggest that the pathways relating central sympathetic influences, are specialized.

Fine structure of the autonomic ganglia of the mouse pulmonary vein

The aim of this study was to describe the architecture of a ganglionated nerve plexus found in the loose connective tissue surrounding the pulmonary vein of the mouse. The input to this plexus was from the vagus nerves and from the stellate ganglia. A large ganglion containing more than 200 neurons was commonly found near the primary bifurcation of the pulmonary vein. The neurons were studied by NADH-diaphorase, zinc iodide-osmium and glyoxylic acid-induced catecholamine fluorescence methods at the light microscopic level, by scanning electron microscopy after the removal of connective tissue, and by transmission electron microscopy. The shape of the neuronal cell bodies was generally a smooth ellipsoid with the average major axis about twice the minor axis. The measured maximum cell diameter ranged from 14 to 42 micron (mean 26 micron). The profile area of individual neurons, as measured from wholemount preparations, ranged from 100 to 800 micron2 (mean 340 micron2) and the calculated neuronal volume ranged from 500 to 12,000 micron3 (mean 3300 micron3). Although there was this wide spread in neuronal size, histograms of cell size showed no separate populations of neurons. Almost all of the ganglionic neuronal cell bodies showed no catecholamine-specific fluorescence, but about 1% of the neurons exhibited a weak green fluorescence. Only a few noradrenergic nerve fibres were seen within the ganglia and these were associated with intraganglionic blood vessels. Small, intensely fluorescent cells were only rarely associated with the ganglia. Neurons and satellite cells formed units which were surrounded by an intraganglionic connective tissue space and a perineurium. Some of the intraganglionic capillaries were fenestrated. Neurons were entirely surrounded by satellite cells and did not appear to have any long dendrites. The generally smooth neuronal cell bodies had short spine-like processes, which were confined to within the satellite cell sheath. Preganglionic nerve fibres formed pericellular baskets of varicose fibres around neurons and made synapses either directly on the cell body or on somatic spines in about equal numbers. No synapses were found in the neuropil at a distance from the neuronal cell body. A few nerve processes were deeply embedded within the neuronal cell body. Clusters of vesicles were found in the cytoplasm of most neurons and were associated with subplasmalemmal densities. These synapse-like structures were mostly directed towards satellite cells, but some were associated with incoming synapses.

[Mechanism of inhibition of cardiac activity by the stellate ganglion in the cat and guinea pig]

In acute and chronic experiments on guinea pigs (43) and cats (49), the stellate ganglion inhibition of the heart activity was revealed to be a consequence of excitation of the vagus cholinergic fibers converging with branches of the stellate ganglion on their route to the heart. Alpha-adrenorecptors were shown to exert no noticeable effect on the heart work. Neither the hypothesis of switching of the sympathetic fibers over to intracardiac cholinergic neurons, nor the hypothesis of the cholinergic link in the mechanism of catecholamines release by the sympathetic nerve terminals, were confirmed. The Dayle principle stating that one neuron exerts its efferent affect by means of one transmitter, seems to be justified.

Overlap of segmental populations and axon collaterals in the thoracic sympathetic system of the cat

Sympathetic preganglionic axons are known to branch in the sympathetic chain, i.e. extraspinally. The possibility that the axons may branch within the spinal cord (intraspinally) and exit through different roots has not been well examined. The purpose of this study was to determine if intraspinal collaterals exist in the distribution of preganglionic neurons innervating the stellate ganglion of the cat using the double-labeled retrograde fluorescent dye technique (Diamidino Yellow and Fast Blue). The right stellate ganglion of pentobarbital-anesthetized cats was isolated; the sympathetic chain was ligated in two places just caudal to the T2 white ramus and then sectioned between the ligatures. One fluorescent tracer was injected into the stellate ganglion; the complementary-colored tracer was injected into the sympathetic chain below the cut. After a 6-day survival time, frozen serial 40-micron sections of spinal cord segments T1-T4 were cut and mounted. The longitudinal distribution of dyes: indicated a segmental preganglionic organization and overlapped approximately 700 micron. However, no sympathetic preganglionic neurons were double-labeled with both dyes. Additional experiments demonstrated a small number of extraspinal preganglionic axon collaterals.

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.

Horseradish peroxidase localization of the sympathetic postganglionic neurons innervating the cat heart

The localization of the sympathetic postganglionic neurons innervating the cat heart has been investigated by using retrograde axonal transport of horseradish peroxidase (HRP). HRP was injected into the subepicardial layers of 4 different cardiac regions. The animals were sacrificed 72-96 h later and fixed by perfusion via the left ventricle. The paravertebral sympathetic ganglia from the superior cervical, middle cervical and stellate ganglia to T10 ganglia were removed and processed for HRP identification. Following injections of HRP into the apex of the heart, the sinoatrial (SA) nodal region and the ventral wall of the right ventricle, we observed that HRP-labeled sympathetic neurons were localized predominantly in the right stellate ganglia, and to a lesser extent, in the right superior and middle cervical ganglia, and left stellate ganglia. Fewer labeled cells were found in the right T4-T6. T8 and T9. After HRP injection into the dorsal wall of the left ventricle, HRP-labeled cells were present mainly in the left stellate ganglia.

Tracing of afferent and efferent pathways in the left inferior cardiac nerve of the cat using retrograde and transganglionic transport of horseradish peroxidase

Retrograde and transganglionic transport of horseradish peroxidase (HRP) was used to trace afferent and efferent pathways in the left inferior cardiac nerve of the cat. Cardiac efferent and afferent neurons were located, respectively, in the stellate ganglion (average cell count per experiment:2679) and in the ipsilateral dorsal root ganglia (DRG) from C8 to T9 (average cell count per experiment:213). Labeled cardiac afferent projections to the spinal cord were most dense in segments T2-T6 where they were located in Lissauer's tract and in lamina 1 on the lateral border of the dorsal horn. Labeled afferent axons extended ventrally through lamina 1 into lamina 5 and the dorsolateral region of lamina 7 in proximity to the intermediolateral nucleus. A weak projection was noted on the medial side of the dorsal horn. These sites of termination are similar to projections by other sympathetic afferent pathways (i.e. renal, hypogastric and splanchnic nerves) to the lower thoracic and lumbar spinal cord, indicating that visceral afferents may have a uniform pattern of termination at various segmental levels. This pattern of termination in regions of the gray matter containing spinothalamic tract neurons and neurons involved in autonomic mechanisms is consistent with the known functions of sympathetic afferent pathways in nociception and in the initiation of autonomic reflexes.

Localization of sympathetic postganglionic and parasympathetic preganglionic neurons which innervate different regions of the dog heart

The locations of sympathetic postganglionic and parasympathetic preganglionic neurons projecting to the heart have not yet been clearly established. Therefore, aliquots of horseradish peroxidase (HRP) were injected into specific regions of the heart, intraventricular cavity, pericardial sac, aortic arch, and the skin in 27 dogs. Following injections into the heart, aorta, or pericardial sac, retrogradely labeled neurons were present in the greatest numbers in the middle cervical ganglia bilaterally. Labeled neurons were located in the cranial poles of the stellate ganglia bilaterally and occasionally in the superior cervical ganglia. Labeled cells were also found in small ganglia located along cardiopulmonary nerves. Injections of HRP into specific areas of the heart did not result in labeling of cells in specific loci of the thoracic or cervical sympathetic ganglia. When the ansae were cut on one side, no labeled cells were found in the ipsilateral stellate ganglion or upper thoracic chain. Following injections into the skin of the left elbow or left cranial nipple, labeled cells were found in the stellate ganglia and the sympathetic chain and in one case in the middle cervical ganglion as well. These data suggest that postganglionic sympathetic neurons which project efferent axons to a specific cardiac region are not located in a specific region of a sympathetic ganglion or a specific sympathetic ganglion. Rather, neurons in one region of a sympathetic ganglion project axons to widespread areas of the myocardium. Sympathetic postganglionic neurons in the stellate ganglion or sympathetic chain project their axons to the heart via the subclavian ansae or interganglionic nerves, not via nerves arising directly from the sympathetic chain. Small numbers of labeled neurons were found in the medulla oblongata, thus indicating that in comparison to sympathetic postganglionic neurons relatively few preganglionic parasympathetic neurons project directly to the heart. When labeled cells were present in the medulla, the majority were located in the ventrolateral nucleus ambiguus.

The nerve loops crossing below the subclavian artery and their anatomical variations

60 dissections analysed the variability of three types of nerve loops crossing beneath the subclavian artery : Vieussens' annulus, the anastomotic ansa between the lower laryngeal nerve and the cervical sympathetic, and the anastomotic ansa between the phrenic nerve and the stellate ganglion. The classic disposition of these loops, situated below the artery and present simultaneously, was found in only 10% of the cases. Though Vieussens' annulus was present in most of the dissections, the anastomotic ansa between the cervical sympathetic and both the lower laryngeal nerve and the phrenic nerve corresponds more rarely to the conventional pattern.

Comparative anatomy of the myenteric plexus of the distal colon in eight mammals

The behavior of the most distal part of the colon in a variety of species suggests that the innervation of this part may differ from that of more proximal parts. Silver impregnation was used to demonstrate the arrangement of the myenteric plexus of the distal colon in eight species (rat, guinea pig, rabbit, Australian possum, American opossum, cat, dog, and monkey). A distal zone, approximately 5%-20% of the total length of the colon above the anal verge in the nonrodents, was characterized by a plexus of very irregularly disposed intersecting nerve bundles of highly variable size with few and small ganglia; this zone was absent in the three rodent species. A next most distal zone, approximately 10%-65% of the total colonic length, contained a stellate plexus of large, regularly disposed ganglia interconnected by small nerve fiber bundles upon which were superimposed large dark-staining nerve bundles; these bundles began to be seen at the level of the irregular rectal plexus and ran cephalad, bypassing some ganglia but giving off branches to others. These, called shunt fascicles, contained many myelinated nerve fibers. Above this zone, the plexus was a stellate plexus throughout the remainder of the colon.

A correlative quantitative study comparing the nerve fibers in the cervical sympathetic trunk and the locus of the somata from which they originate in the rat

Correlative quantitative analyses were performed on the rat comparing the number of fibers in the cervical sympathetic trunk (CST) and the horseradish peroxidase (HRP)-labeled neurons in the superior cervical sympathetic ganglion (SCG), stellate ganglion, as well as in the spinal cord. The total number of nerve fibers in the left CST was 4180 +/- 169 (mean +/- S.E.M.) among which 92 +/- 3 (mean +/- S.E.M.) were myelinated. The diameter of unmyelinated fibers was 0.68 +/- 0.22 (mean +/- S.D.) microns and showed single-peaked distribution. After the application of HRP to the proximal cut end of the CST, labeled neurons were found in the stellate ganglion as well as in the ipsilateral spinal cord from C7 to T4 segments. The total number of HRP-labeled neurons in the spinal cord was 1334 +/- 45 (mean +/- S.E.M.) with the range between 844 and 1808. Ninety-nine percent of labeled neurons were located in the intermediolateral column and in the lateral funiculus while 1% were in the intercalated region and central autonomic area. Labeled neurons were encountered only sporadically in the dorsal root ganglia (DRG) from C8 to T3 level. After the application of HRP to the distal cut end of the CST, about 200 labeled neurons were observed in the caudal part of the SCG. The present results were discussed with special reference to the organization of the CST of the rat.

The distribution of the sympathetic preganglionic neurons projecting onto the stellate ganglion of the guinea pig. A horseradish peroxidase study

After injection of horseradish peroxidase (HRP) into the stellate ganglion (SG) of the guinea pig, labelled cells were found in the C8-T11 spinal cord segments. The HRP-positive neurons were located in the nucleus intermedio-lateralis pars principalis and funicularis (ILp and ILf) and in the nucleus intercalatus proprius and pars paraependymalis (ICp and ICpe). The ICp and ICpe neurons represented approximately one-fourth of the total number of labelled cells. The ILp and ILf neurons were mainly located in the T2 and T3 segments whereas the ICp and ICpe neurons occurred mainly in the T4 to T6 segments where the ICpe cell group formed a continuous cell column dorsal to the central canal. The possible correlation between the segmental distribution and peripheral sympathetic effects was discussed.

Cardiac and non-cardiac preganglionic neurones of the thoracic vagus nerve: an HRP study in the cat

Using the HRP method, we studied cardiac and non-cardiac preganglionic neurones of the thoracic vagus nerve in the cat. The inferior cardiac branches of the right thoracic vagus nerve were differentiated from the neighboring non-cardiac branches by positive cardiac slowing following electrical stimulation. A small amount of crystalline HRP was placed at the central cut end of the cardiac or non-cardiac branches. After a survival period of 2 days, the medulla oblongata, the stellate ganglion (SG), the superior cervical (SCG) and the nodose ganglion (NG) were serially sectioned and processed for histochemical demonstration of HRP. In the medulla oblongata, HRP-labeled cells were mainly located in 2 regions: (1) within and around the ambiguous complex (site A); (2) within the dorsal vagus nucleus (site X). After applying HRP to the cardiac branches, 968 HRP-labeled cells were observed in 7 animals bilaterally with the ipsilateral dominance (94%); 81% of them were found in site A. After applying HRP to the non-cardiac branches, 447 HRP-labeled cells were seen in 2 animals bilaterally with the ipsilateral dominance (92%); 79% of them were found in site X. Many HRP-labeled cells were found in the SG and NG, indicating that the cardiac branches are composed of sensory afferent and sympathetic efferent fibres as well as cardiac vagus efferent fibres.