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Topographic relationship of neurotensin-containing axon terminals with cardiac and noncardiac principal ganglion cells in the stellate ganglia of the cat.

The pattern of association between neurotensin (NT)-immunoreactive (NTIR) preganglionic nerve terminals and cardiac and noncardiac neurons in the stellate ganglion of the cat is analyzed, based on the finding of an excitatory modulation effect of exogenous NT on cardiac functions. For this purpose, NT-containing terminals were labeled by immunohistochemistry, and ganglion cells were detected by retrograde labeling of cardiac and vertebral nerves to identify cardiac and noncardiac neurons. To determine a possible regional localization of NTIR terminals and ganglion cells, the ganglia were divided into four areas: caudal, dorsomedial, cranial, and ventromedial, related to the two major afferent nerves (thoracic white rami 3 [T3WR] and 2 [T2WR]) and the two efferent nerves (vertebral and cardiac). NTIR terminals were widespread in the complete ganglion tissue; they covered practically all the regions explored, although two clusters of high concentration of NTIR terminals were detected in the cranial and caudal areas. By retrograde labelling it was found that cardiac cells were arranged around the exit of the cardiac nerve and that the vertebral neurons were extended from the exit of the vertebral nerve to the entrance of T3WR. The finding of association of NTIR terminals with cardiac neurons may account for the cardioregulatory effect of NT; however, since the presence of NTIR terminals close to the noncardiac neurons is notorious, other regulatory functions of NT must be considered.

Animals↗

Triggers of ventricular tachyarrhythmias and therapeutic effects of nicorandil in canine models of LQT2 and LQT3 syndromes.

OBJECTIVES: We sought to identify the triggers of ventricular tachyarrhythmia (VTA) in experimental models of long QT type 2 (LQT2) and long QT type 3 (LQT3) syndromes. BACKGROUND: Most adverse cardiac events occurring in the long QT type 1 syndrome are related to sympathetic nerve activity. In contrast, various factors may trigger VTA in patients with LQT2 and LQT3. METHODS: The mode of onset of VTA and therapeutic effects of the potassium-adenosine triphosphate channel opener nicorandil were compared in canine models of LQT2 and LQT3, using three induction protocols: 1) bradycardia produced by atrioventricular block (BRADY); 2) programmed ventricular stimulation; and 3) electrical stimulation of the left stellate ganglion (left stellate stimulation [LSS]). Transmural unipolar electrograms were recorded, and the activation-recovery interval (ARI) was measured. RESULTS: Ventricular tachyarrhythmias developed during BRADY in all six experiments in the LQT3 model, but in none of the six experiments in LQT2. Programmed ventricular stimulation induced VTA in two experiments of the LQT2 model, but in none of the LQT3 experiments. Stimulation of the left stellate ganglion induced VTA in three experiments in LQT2 and in two experiments in LQT3. Nicorandil caused greater shortening of ARI and greater attenuation of transmural ARI dispersion in the LQT2 model than in the LQT3 model. After treatment with nicorandil, a single VTA was induced in the LQT2 model by LSS, whereas in the LQT3 model, VTA remained inducible by BRADY in four experiments and LSS in one experiment. CONCLUSIONS: An abrupt increase in sympathetic activity appeared arrhythmogenic in both models. Nicorandil attenuated the heterogeneity of ventricular repolarization and suppressed the induction of VTA in the LQT2 model, but had a limited therapeutic effect in the LQT3 model.

Animals↗

Evidence that sympathetic preganglionic neurones are arranged in target-specific columns in the thoracic spinal cord of the rat.

It is recognised that selective activation of different target-specific sympathetic preganglionic neurones forms the basis of many autonomic responses. The anatomical basis for this could be the spatial arrangement of these neurones in the spinal cord nuclei. The present study tested this possibility in the rat by determining the location in single animals of three distinct groups of sympathetic preganglionic neurones, one group projecting to the superior cervical ganglion, another to the stellate ganglion and one to the adrenal medulla. Sympathetic preganglionic neurones to each of these targets were simultaneously labeled with fluorescent dyes, either Fluorogold, Fast Blue, or Diamidino Yellow. The numbers and general morphology of the neurones were similar to previous descriptions, and they were distributed in four subnuclei, the nucleus intermediolateralis pars principalis, the nucleus intermediolateralis pars funiculus, the nucleus intercalatus spinalis, and the nucleus intercalatus spinalis pars paraependymalis. It was shown that all three groups of neurones were represented in the more medial sympathetic nuclei, but in the nuclei at the lateral border of the intermediate grey matter each one of the three groups of neurones occupied a discrete location. Adrenal medullary sympathetic preganglionic neurones occupied a lateral aspect, the superior cervical ganglion sympathetic preganglionic neurones a medial aspect, and the stellate ganglion sympathetic preganglionic neurones a space between. Some sympathetic preganglionic neurones were double labeled after dye injections into the superior cervical and stellate ganglion thus indicating that they projected to both ganglia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Immunohistochemical demonstration of choline acetyltransferase-immunoreactive preganglionic nerve fibers in guinea pig autonomic ganglia.

The distribution of choline acetyltransferase (ChoAcTase)-like immunoreactivity in the superior cervical ganglion and the stellate ganglion was analyzed with immunohistochemistry. A dense network of ChoAcTase-immunoreactive nerve fibers was observed in both ganglia studied. The ChoAcTase-positive fibers were found in all parts of the ganglia but had a differential distribution, giving rise to a patchy staining pattern. After preganglionic denervation of the superior cervical ganglia, all ChoAcTase-positive fibers disappeared. For comparison, the distributions of enkephalin- and neuropeptide Y-like immunoreactivity were analyzed. In the stellate ganglion, the enkephalin-positive fibers had a marked regional distribution. Areas with the highest enkephalin-fiber density seemed to contain low numbers of ChoAcTase-positive fibers and vice versa. The findings give evidence for occurrence of acetylcholine synthesis in preganglionic fibers in paravertebral sympathetic ganglia.

Acetylcholine↗

Scintigraphic assessment of regional cardiac adrenergic innervation.

To assess the feasibility of noninvasively imaging the regional distribution of myocardial sympathetic innervation, we evaluated the distribution of sympathetic nerve endings, using 123I metaiodobenzylguanidine (MIBG), and compared this with the distribution of myocardial perfusion, using 201Tl. Twenty dogs were studied: 11 after regional denervation, and nine as controls. Regional denervation was done by left stellate ganglion removal, right stellate ganglion removal, and application of phenol to the epicardial surface. Computer-processed functional maps displayed the relative distribution of MIBG and thallium in multiple projections in vivo and excised heart slices in all animals. In six animals, dual isotope emission computed tomograms were acquired in vivo. Tissue samples taken from innervated and denervated regions of the MIBG images were analyzed for norepinephrine content to validate image findings. Normal controls showed homogeneous and parallel distributions of MIBG and thallium in the major left ventricular mass. In the left stellectomized hearts, MIBG was reduced relative to thallium in the posterior left ventricle; whereas in right stellectomized hearts, reduced MIBG was in the anterior left ventricle. Phenol-painted hearts showed a broad area of decreased MIBG extending beyond the area of phenol application. In both stellectomized and phenol-painted hearts, thallium distribution remained homogeneous and normal. Norepinephrine content was greater in regions showing normal MIBG (550 +/- 223 ng/g) compared with regions showing reduced MIBG (39 +/- 44 ng/g) (p less than 0.001), confirming regional denervation. Combined MIBG-thallium functional maps display the regional distribution of sympathetic innervation. This new ability to noninvasively map the distribution of sympathetic nerves with simultaneous comparison to regional perfusion may provide important new insights into mechanisms, whereby an imbalance in sympathetic activity may relate to clinical disorders.

3-Iodobenzylguanidine↗

Localization of sympathetic postganglionic neurons of physiologically identified cardiac nerves in the dog.

Cardiac nerves were identified physiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labelphysiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labelphysiologically and injected with horseradish peroxidase in 38 dogs. Retrogradely labeled neurons were present in the greatest number in the middle cervical ganglion, whereas fewer labeled neurons were present in the stellate ganglion. Only occasional neurons in the superior cervical ganglion were labeled, and no labeled cells were found in the T3 to T6 paravertebral ganglia or in the ganglia contralateral to the nerve injected. following injections into specific cardiac nerves, retrograde labeling was widespread within the middle cervical ganglion, and the distributions of labeled neurons from different nerves overlapped considerably. In the middle cervical ganglion there was little or no regional grouping of cells projecting to specific cardiac nerves. within the stellate ganglion, however, te cardiac-sympathetic cells were clustered primarily at the cranial pole near toe origin of the ventral and dorsal ansae. Mediastinal ganglia and ganglia located in cardiac nerves were frequently as heavily labeled as the ipsilateral stellate ganglion. The occurrence of heavy labeling in mediastinal and cardiac nerve ganglia indicates that these hitherto unreported ganglia play a significant role in cardiac neural regulation. These data imply that the organization of sympathetic neurons controlling the heart is much more complex than has previously been considered.

Animals↗

Addition of dexmedetomidine prolongs duration of vasodilation induced by sympathetic block with mepivacaine in dogs.

BACKGROUND AND OBJECTIVES: The aim of this study was to examine the duration of vasodilation induced by sympathetic block with the addition of dexmedetomidine to mepivacaine. METHODS: We measured right and left brachial artery blood flow (BABF) before and after stellate ganglion block used as a sympathetic block in dogs. The experimental protocol was designed as follows: (1) left stellate ganglion block using 1.0 mL 0.5% mepivacaine (n = 8), (2) left stellate ganglion block using the addition of dexmedetomidine 0.5 microg to 1.0 mL 0.5% mepivacaine (n = 8), and (3) left stellate ganglion block using the addition of dexmedetomidine 0.5 microg to 1.0 mL physiological saline solution (n = 8). RESULTS: Left stellate ganglion block with mepivacaine alone increased left BABF significantly from 5 minutes through 50 minutes after the block (baseline, 100%; peak at 10 minutes after SGB, 181 +/- 27%; P <.01). Left stellate ganglion block with the addition of dexmedetomidine to mepivacaine induced a significant increase of left BABF from 5 minutes through 90 minutes after the block (baseline, 100%; peak at 10 minutes after SGB, 174 +/- 36%; P <.01). Left and right BABF did not change significantly after stellate ganglion block with dexmedetomidine only. Right BABF decreased significantly after left stellate ganglion block with mepivacaine alone or the addition of dexmedetomidine to mepivacaine throughout the study. CONCLUSIONS: The addition of dexmedetomidine prolongs the duration of vasodilation induced by stellate ganglion block with mepivacaine used for sympathetic block in dogs.

Analgesics, Non-Narcotic↗

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.

Animals↗

Current status of thoracic dorsal sympathectomy.

This article summarizes over 20 years of experience (1962 to 1982) with cervical sympathectomy (thoracic dorsal sympathectomy) in 46 patients undergoing 68 sympathectomies. All operations were performed through an anterior supraclavicular approach. Indications for surgery were intractable Raynaud's disease (26 patients), atherosclerotic obliterative arterial disease (five), causalgia (five), posttraumatic sympathetic dystrophy (seven), collagen vascular disorders (eight), hyperhidrosis (12), occupational-related digital thrombosis (four), and thrombosis secondary to intra-arterial injection (one). The incidence of complications and side effects, both temporary and permanent, including Horner's syndrome, is reviewed in detail. Particular reference is made to the various surgical techniques of managing the stellate ganglion; four patients had two-third to three-fourth resection of the stellate ganglion down to and including the T-3 thoracic ganglion, two had preservation of the stellate ganglion and resection of the T-2 through T-4 ganglia, seven had excision of the entire stellate ganglion down to and including the T-4 ganglion, seven had resection of the lower third of the stellate ganglion down to and including the T-4 ganglion, and 48 had removal of the lower half of the stellate ganglion down to and including the T-3 ganglion. The study reviews the literature germane to anatomic considerations and suggests revisions in current texts and atlases. By retrospective analysis of the records and a follow-up questionnaire, which provided an 86% follow-up (average 8.4 years), the paper points to the distinctive clinical characteristics of the different groups within the population undergoing the operation and provides guidelines for patient selection and conclusions on the place for this operation in the management of vascular diseases involving the upper extremity.

Adult↗

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.

Animals↗

Network of the sympathetic nervous system: focus on the input and output of the cervical sympathetic ganglion.

Unlike the thoracic and lumbar sympathetic nervous systems with paravertebral ganglions in individual spinal segments, the cervical sympathetic nervous system lacks segmental structures corresponding to the spinal segments and only three ganglions, namely the upper and middle cervical ganglions and the stellate ganglion, are present. Single axons have been observed in the ganglions using an anterograde-labeling method to analyze their expansion in order to investigate the relationship between the cervical sympathetic ganglions and the spinal cord in rats. Although segmental structures were not confirmed in the upper cervical ganglion, segmental structures were demonstrated in the stellate ganglion. Next, it was determined that some sympathetic preganglionic neurons, nitric oxide synthetase-positive preganglionic neurons, form dense nerve endings on the upper cervical ganglion neurons that project onto organs closely related to glandular secretion in the head and neck region. Finally, the relationship between the cell body size of upper cervical ganglion neurons and the size of the target was investigated for the three major salivary glands in rats and it was determined that no direct relationship was present.

Animals↗

Comparing the somal size and nuclear positions of the monkey stellate and coeliac ganglion cells.

The stellate and coeliac ganglia of 2 Macaque monkeys were cut serially at 1 micron thickness and analysed. Results from the analysis of 82 stellate and 60 coeliac ganglion cells in 1 monkey show that in cross-sections, the neuronal nuclei may be eccentric, centric or nearly centric and remain so throughout the longitudinal extent of the neuron. In both ganglia, the majority of neurons possess eccentric nuclei, but in the coeliac ganglion, the percentage of neurons with centric and/or nearly centric nuclei is higher (41.7%) than that in the stellate ganglion (26.3%). While 5% of neurons in the coeliac ganglion are binucleated, no binucleated neurons were found in the stellate ganglion. The somal size ranges of the stellate (10-39 microns) and the coeliac (14.5-45 microns) ganglion neurons as obtained from both monkeys are quite close. The percentage frequency distribution of the stellate ganglion neurons in monkey 1 was also quite similar to that of the coeliac ganglion neurons. It is concluded that different neuronal size is not likely to be associated with different target organs.

Animals↗

[Asymmetry of the neuronal organization of the cat stellate (cervicothoracic) ganglion in the postnatal period of ontogenesis].

By direct and indirect morphometry the cell density maximal diameter and area of section of neurocytes in the zones of the emergence of the basic nerves and in the centre of the stellate ganglion were determined in kittens of various ages and adult cat. There is an increase of the maximal diameter, average area of section of neurons (16.98 +/- 0.07 mm and 132.2 +/- 0.9 mm2 in newborn, 21.7 +/- 0.72 mm and 31.4 +/- 2.6 mm2 in 10-days, 6.69 +/- 0.5 mm and 355 +/- 2.4 mm2 in 20-days kitten, 4.86 +/- 0.6 mm and 634 +/- 36 mm2 in adult cat and reduction of cell density of ganglionic neurons in postnatal ontogenesis. In newborn kitten, kittens of 10- and 20-days of age and adult cat larger neurons were located in the cranial part of the ganglion. In 10 and 20 days kittens and adult cats an asymmetry between right and left stellate ganglia in the maximal diameter and average area of section of neurons was revealed. In adult cat the asymmetry in the cell density was also found between both ganglia.

Animals↗

Dispersion of refractoriness in canine ventricular myocardium. Effects of sympathetic stimulation.

In 18 dogs on total cardiopulmonary bypass, the average interval between local activations during artificially induced ventricular fibrillation (VF interval) was measured from extracellular electrograms, simultaneously recorded from up to 32 ventricular sites. VF intervals were used as an index of local refractoriness, based on the assumption that during ventricular fibrillation, cells are reexcited as soon as they have recovered their excitability. In support of this, microelectrode recordings in two hearts during ventricular fibrillation did not show a diastolic interval between successive action potentials. Refractory periods determined at a basic cycle length of 300 msec with the extrastimulus method correlated well with VF intervals measured at the same sites. Thus, this technique allows assessment of spatial dispersion of refractoriness during brief interventions such as sympathetic stimulation. The responses to left, right, and combined stellate ganglion stimulation varied substantially among individual hearts. This was observed both in dogs with an intact (n = 12) and decentralized (n = 6) autonomic nervous system. Individual ventricular sites could show effects of both left and right stellate ganglion stimulation (42% of tested sites) or show effects of left-sided stimulation only (31%) or right-sided stimulation only (14%). In 13% of sites, no effects of stellate stimulation were observed. Apart from these regional effects, the responses could be qualitatively different; that is, within the same heart, the VF interval prolonged at one site but shortened at another in response to the same intervention, although shortening was the general effect and prolongation the exception. Whenever sites responded to stellate ganglion stimulation with a shortening of VF interval, this shortening was approximately 10% for left, right, or combined stimulation, whether the autonomic nervous system was intact or decentralized. In six of 12 hearts in the intact group, there was a distinct regional effect of left stellate ganglion stimulation; in the other six hearts, the effects were distributed homogeneously over the ventricles. In three hearts, the effect of left stellate ganglion stimulation was strongest in the posterior wall, and in the other three hearts, in the anterior wall. The effects of right stellate ganglion stimulation were restricted to the anterior or lateral part of the left ventricle. Dispersion of VF intervals increased after left and combined stellate ganglion stimulation in the intact group and after right stellate ganglion stimulation in the decentralized group, but not significantly in every heart. This points to a marked individual variation with regard to the effects of sympathetic stimulation on electrophysiological properties of the heart.

Action Potentials↗

Interaction of sympathetic and parasympathetic nervous system on ventricular refractoriness assessed by local fibrillation intervals in the canine heart.

OBJECTIVE: The aim was to assess the effects of autonomic nerve stimulation on local ventricular refractoriness by measuring local ventricular fibrillation intervals. METHODS: In 10 dogs on cardiopulmonary bypass, ventricular fibrillation intervals were recorded simultaneously at up to 32 sites before and after neural stimulation. In four dogs (group 1) the response to bilateral stellate ganglion stimulation was measured before and after bilateral cervical vagotomy. In three dogs (group 2) bilateral stellate ganglion stimulation, vagal nerve stimulation, and combined vagal and stellate ganglia stimulation were performed. In three dogs (group 3) the same protocol was applied after total decentralisation of the autonomic nervous system. RESULTS: Bilateral stellate ganglion stimulation shortened the ventricular fibrillation interval at 44-50% of myocardial sites before and after vagotomy, whereas prolongation of the interval was observed at 14-18% of the sites. At higher stimulus strength shortening of the interval was measured at 85% of the sites in the intact and decentralised groups. No prolongation was observed. The shortening was largest in the decentralised group (11.1 ms). Dispersion in refractoriness increased in hearts from all groups, but not in each individual heart. Left, right, or bilateral vagal stimulation was without effect at about 75% of the tested sites. The fact that the response to autonomic nerve stimulation varies from site to site warrants our approach of simultaneous recordings at multiple sites. Dispersion in refractoriness was not affected by vagal stimulation. Combined autonomic stimulation had approximately the same effect on dispersion in refractoriness as bilateral stellate ganglion stimulation alone. However, vagal stimulation attenuated the responses to bilateral stellate ganglion stimulation by some 20% in the decentralised group. CONCLUSIONS: Vagal stimulation has minor effects on ventricular refractoriness, but this is not due to sparse innervation, since vagal stimulation is able to mitigate the effects of sympathetic stimulation in decentralised hearts.

Animals↗

Sympathetic neural effects on regional atrial recovery properties and cardiac rhythm.

The functional distribution of the cardiac sympathetic nerves to the atria and their arrhythmiogenic effects were determined in 16 open-chest pentobarbital-anesthetized dogs. Shortening of refractory periods at four right and two left atrial sites during stimulation of the nerves was taken as a criterion of their distribution. Stimulation of right stellate ganglion, craniovagal, and right stellate cardiac nerves produced localized shortening on the right atrium, particularly at the sinus node area, and invariably induced sinus tachycardia. The recurrent cardiac nerve produced little shortening at all sites and less arrhythmiogenic effect. The left stellate ganglion and ventrolateral cardiac nerve affected only left atrial sites and induced atrioventricular junctional rhythm. The ventromedial cardiac nerve affected all sites and had no consistent arrhythmiogenic effect. The innominate nerve had no substantial effect. We concluded that the functional distribution of the cardiac sympathetic nerves is localized, and that rate, rhythm, and refractory period changes induced by stimulation of these nerves are characteristic of the area of distribution.

Animals↗

Vasoactive intestinal peptide and neuropeptide Y coexist in non-noradrenergic sympathetic neurons to guinea pig trachea.

Vasoactive intestinal peptide (VIP) has been suggested to be a mediator of vagal inhibition of airway tone and it has been assumed that VIP-containing nerve fibres in the airway arise from intrinsic ganglia. We have used a combination of double- and triple-labelling immunohistochemistry, retrograde axonal tracing, organotypic culture and nerve lesion studies, to identify the origin and distribution of neurons containing immunoreactivity (IR) to VIP in guinea pig airway smooth muscle. We also investigated whether immunoreactivity to other neuropeptides coexisted with VIP-IR within these neurons. We found that all VIP-IR nerve fibres in guinea pig tracheal smooth muscle also contained IR to neuropeptide Y (NPY) but not to tyrosine hydroxylase (TH), a marker for noradrenergic neurons. Both VIP-IR and NPY-IR were absent from nerve cell bodies in the tracheal plexus. After maintenance of isolated trachea in organotypic culture for 4 days, to allow degeneration of extrinsic nerve fibres, nerve fibres containing VIP-IR or NPY-IR were almost completely absent from tracheal smooth muscle. Of ganglia known to supply the trachea, coexistence of VIP-IR and NPY-IR was found only in cell bodies of the stellate ganglion. Retrograde tracing studies using the fluorescent tracer, DiI, confirmed that the stellate ganglion was the site of origin of neurons containing VIP-IR and NPY-IR supplying the airways. These neurons projected to the airways from the stellate ganglion both directly through the mediastinum, and via the cervical sympathetic trunk and vagus nerves. These results suggest that nerve fibres containing both VIP-IR and NPY-IR in the tracheal smooth muscle of the guinea pig are derived from non-noradrenergic cell bodies in the stellate ganglion. The absence of VIP-IR from vagal post-ganglionic neurons suggests that VIP cannot be a mediator of vagal inhibitory transmission in tracheal smooth muscle of this species.

Animals↗

The localization of sympathetic and vagal neurones innervating the carotid sinus in the rabbit.

The distribution of neurones innervating the carotid sinus of the rabbit was determined by inserting chips of horseradish peroxidase (HRP) into the adventitial layer of the carotid sinus. Labelled neurones were found in the superior cervical ganglion, along the cervical sympathetic trunk and in the nodose ganglion (mean counts of 1876, 139 and 232, respectively). No labelled neurones were located in the middle cervical ganglion or the stellate ganglion. Within the superior cervical ganglion, the fraction of labelled neurones found in equal longitudinal quadrants of the ganglion were, from rostral to caudal, 2%, 12%, 42% and 44%. Thus the majority of neurones were located in the caudal region of the superior cervical ganglion. The primary pathway for sympathetic fibres innervating the carotid sinus was shown to be in branches of the external carotid nerve. The greatest number of labelled neurones in the nodose ganglion were located in the most rostral quadrants of the ganglion.

Animals↗