Effects of Denervation and Axotomy on Nervous System-Specific Protein, Ornithine Decarboxylase, and Other Enzyme Activities in the Superior Cervical Sympathetic Ganglion of the Rat

The time courses of changes of three enolase isozymes (alpha alpha, alpha gamma, and gamma gamma), S-100 protein, 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), ornithine decarboxylase (ODC), beta-galactosidase, and glucose-6-phosphate dehydrogenase (G6PDH) were examined from 1 to 14 days after cutting of the preganglionic nerve (denervation) or the postganglionic nerve (axotomy) of the superior cervical sympathetic ganglion (SCG) of the rat. The wet weight and protein content in the axotomized SCG increased continuously, to nearly twice those of the denervated SCG for 1-2 weeks after the operations. Among enolase isozymes in the SCG, neuron-specific gamma gamma-enolase decreased rapidly after denervation and stayed at a low level for 2 weeks, whereas the isozyme remained almost unchanged after axotomy. On the contrary, ganglionic alpha alpha-enolase and the alpha gamma-hybrid form increased remarkably to reach a maximum at the second day after axotomy, and remained above control for 1 to 2 weeks; these two enolase isozymes showed little change after denervation. Denervation caused a much larger increase than did axotomy in the ganglionic S-100 protein, an astrocyte-specific protein, during the first week after the operation, while the protein content decreased after 2 weeks of either denervation or axotomy. CNPase, a myelin-associated enzyme, rose suddenly 2 days after axotomy, and remained at a rather high level compared with the denervated ganglion, which showed little variation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Retrograde Transport of Endogenous Nerve Growth Factor in Superior Cervical Ganglion of Adult Rats

The concentration of naturally synthesized nerve growth factor (NGF) was measured in various tissues of adult rats, using a highly sensitive two-site enzyme immunoassay. The highest concentration was found in the superior cervical sympathetic ganglion (SCG). Transection of the postganglionic external carotid nerve (ECN) reduced the ganglionic level of NGF more than did section of the internal carotid nerve (ICN). When both the preganglionic nerve and the ECN were cut, the ganglionic NGF level decreased even more. On the other hand, when the preganglionic nerve and the ICN were both sectioned, leaving the ECN intact, endogenous NGF content in the SCG was significantly enhanced 3-9 h after operation. Bilateral extirpation of submaxillary gland produced a rapid decrease in ganglionic NGF 3-6 h after operation, and even unilateral removal of one salivary gland caused a decrease in both ganglia, which was however much greater in the ipsi- than in the contralateral ganglion. Removal of the eyeballs caused a much smaller reduction in ganglionic NGF than did removal of the glands. These results suggest that the endogenous NGF that accumulates in the SCG is mostly synthesized in the submaxillary gland rather than in the iris, and that it is transported to the SCG, mostly via the ipsilateral ECN.     

A quantitative study of the developmental expression of nerve growth factor (NGF) receptor in rats

The developmental expression of nerve growth factor (NGF) receptor was quantitated in either homogenates or plasma membrane-enriched preparations from whole rat embryos or from isolated tissues. The assay involved crosslinking 125I-NGF to receptors followed by immunoprecipitation with a monoclonal antibody to rat NGF receptor. In some cases, the pellet was resuspended and subjected to a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) autoradiographic analysis. The NGF receptor was found in whole embryo homogenates as early as embryonic Day 10 (E10) (earliest age examined). The NGF receptor content in whole embryos per milligram protein increased about 3-fold from E11 to E18 and decreased slightly at E20. SDS-PAGE autoradiography showed that the molecular weights of 125I-NGF-bound receptors did not vary with age. The NGF receptor content in sciatic nerve homogenates decreased 23-fold from newborn to adulthood. The change of NGF receptor level in hindleg muscle had a profile similar to that seen in sciatic nerve. The NGF receptor content in superior cervical ganglion (SCG) or dorsal root ganglion (DRG) homogenate preparations was expressed in two ways. On a per milligram protein basis, in SCG, the receptor density was decreased slightly from E20 to adulthood; in DRG, it was relatively constant from E15 through postnatal Day 0 (PND-0) and then dropped 6.7-fold in adults. On a per ganglion basis, in SCG, it increased 4.4-fold from E20 to adult; in DRG, it increased 9-fold from E15 to PND-0 and then stayed constant through adulthood. In brain membrane preparations, the NGF receptor level decreased 11-fold from E15 to adulthood. In spinal cord membrane preparations, it decreased 7-fold from E18 to adulthood. Levels of receptor in cord were always greater than in brain. These data suggest that alterations in the NGF receptor density may have a role in changes in tissue responsiveness to NGF during development.     

Appearance of retrogradely labeled neurons in the rat superior cervical ganglion after injection of wheat-germ agglutinin-horseradish peroxidase conjugate into the contralateral ganglion

Summary Injection of wheat-germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the superior cervical ganglion (SCG) of the rat results in accumulation of WGA-HRP in sympathetic postganglionic neurons in the contralateral SCG. The sympathetic pathways involved and the mechanism underlying the labeling were investigated. The labeling in neurons in the contralateral SCG was apparent 6 h after injection and increased in intensity with longer survival times. The number of labeled neurons reached 1300 at 72 h after the injection. Transection of the external (ECN) or internal carotid nerves (ICN) resulted in considerable reduction in the number of labeled neurons. Combined transection of both ECN and ICN virtually eliminated labeling in the contralateral SCG. This provides strong evidence that these two nerves are the major pathways for WGA-HRP transport out of the SCG. No labeling was observed in the contralateral SCG following injection of horseradish peroxidase (HRP). Therefore, it seems unlikely that a direct nerve connection exists between the bilateral ganglia. Instead, the labeling of contralateral SCG neurons appears to depend on the transneuronal transport capacity of WGA-HRP, which conveys the marker in an anterograde direction along the postganglionic fibers to terminals in sympathetic target organs, and then delivers it transneuronally to contralateral SCG neurons. We suggest that the sympathetic nerve fibers originating in the bilateral SCGs run intermingled and are in close contact in their peripheral target organs.     

Stimulation of Transglutaminase Activity by GM1-Ganglioside and α-Sialylcholesterol in Superior Cervical and Nodose Ganglia Excised from Adult Rat

Changes in transglutaminase (TG) activity in superior cervical ganglia (SCG) and nodose ganglia (NG) excised from adult rats were examined following application of selected membrane transport-altering agents, including GM1-ganglioside (GM1) and alpha-sialylcholesterol (alpha-SC). Although TG activity of freshly dissected SCG and NG was relatively low, it increased gradually during 30 min of incubation, and it stayed at this elevated level for 2 h. Addition of alpha-SC at its maximal effective concentration, 20 microM, stimulated TG activity more than eightfold in SCG and more than twofold in NG by 30 min. Addition of GM1 at its most effective concentration, 5 nM, had similar effects, but of lesser magnitude. Cycloheximide, a potent inhibitor of protein biosynthesis, did not affect the GM1- or alpha-SC-evoked increases in ganglionic TG activity, suggesting that enzyme activation rather than synthesis of new enzyme was occurring. The stimulation of TG activity in both ganglia caused by either GM1 or alpha-SC was associated with a decrease in Km and an increase in Vmax values. Addition of cholera toxin B, which specifically masks the oligosaccharide chain of GM1, reduced the GM1-induced increase in TG activity by approximately 60% in SCG and 88% in NG. The alpha-SC-induced increase in TG activity was only partially mimicked by free cholesterol. Although application of either dibutyryl cyclic AMP or dibutyryl cyclic GMP produced little change in TG activity of either ganglion, phorbol ester clearly inhibited the enzymic activity. Because TG is a calcium-dependent enzyme, we measured 45Ca2+ influx into either ganglion, and found that it was reduced by GM1 and alpha-SC in SCG and by alpha-SC in NG.(ABSTRACT TRUNCATED AT 250 WORDS)     

Acetylcholine content in superior cervical ganglion following reinnervation of vagal afferent fibers in cat

The superior cervical ganglion (SCG) was reinnervated by vagal afferent fibers by cross anastomosis between the cranial end of nodose ganglion and the caudal end of SCG in cats. Formation of functional synapses was evidenced by unilateral mydriasis and contraction of the nictitating membrane in response to inflation of the stomach with a balloon or to electrical stimulation of the afferent vagus. The acetylcholine (ACh) content in the cross-anastomosed SCG (reinnervated by vagal afferent fibers) was measured. In anastomosed SCG, the ACh content was about half of normal SCG, but significantly higher than chronically decentralized SCG. Also the ACh content in nodose ganglion (NDG) was investigated in situations in which there was anastomosis, chronic supra, infra, or supra-/infranodose vagotomy. The ACh content of anastomosed NDG was near that of supranosdose vagotomized ganglion. The ACh content of supra-/infranodose vagotomized NDG, which can be considered the NDG itself, was as much as that of normal intact NDG. It was found that the ACh content of infranodose vagotomized NDG was increased, possibly the result of vagal efferent axonal flow or transport. The ACh content of vagal trunk with or without infranodose vagotomy was also measured. The ACh content of vagal trunk with infranodose vagotomy was smaller than that of the normal trunk, but there was still a considerable quantity of ACh. There was no significant change in wet weight of the SCG and NDG before or after the operations. From these results we have concluded that the transmission of the cross-anastomosed SCG (reinnervated with vagal afferent nerve) was cholinergic; and that the vagal afferent nerve have afferent cell bodies not only in NDG but also in peripheral vagal trunks (infranodose portion). These results strongly suggest that vagal afferent fibers are in part cholinergic.     

A COMPARISON OF THE NEURAL REGULATION OF TYROSINE HYDROXYLASE ACTIVITY IN SYMPATHETIc GANGLIA OF ADULT MICE AND RATS

Surgical decentralization of the superior cervical ganglion (SCG) in rats and mice led to a fall in ganglionic tyrosine hydroxylase (T-OH) activity, and a loss of more than 90 per cent of the preganglionic neurone marker, choline acetyl transferase. T-OH activity was reduced by more than 50 per cent in mice SCG ten days after surgery, but fell by only 25 per cent in rat SCG after 21 days. The surgical procedure did not cause obvious histo-logical damage or loss of SCG cells in either species. Both T-OH and choline acetyl transferase activities in rat and mouse SCG recovered to normal three months after surgery. Reserpine treatment was more effective in rats in causing increased ganglionic T-OH activity than in mice. Neither decentralization nor reserpine treatment caused any changes in DOPA-decarboxylase or monoamine oxidase activities in rat SCG. These results demonstrate that T-OH activity in SCG is subject to trans-synaptic regulation in both rats and mice; this regulation does not apply to DOPA-decarboxylase or monoamine oxidase. Differences in basal sympathetic tone may explain the different results obtained in mice and rats.     

Effects of various kinds of stimulation on ornithine decarboxylase activity in superior cervical sympathetic and nodose ganglia of rats

Levels of cyclic nucleotides and ornithine decarboxylase (ODC) activity were examined following the application of various kinds of stimuli to superior cervical sympathetic ganglia (SCG), nodose ganglia, and vagus nerve fibers excised from the rat. The level of cyclic GMP in the SCG rose rapidly to about 4.5- to 7.5-fold the unstimulated control with 10 min of incubation after applications of preganglionic electrical stimulation (10 Hz), acetylcholine (ACh; 1 mM), or high extracellular K+ ( [K+]0, 70 mM). The cyclic GMP level in nodose ganglia was increased less than in the SCG by either ACh or high [K+]0 but was not affected by ACh in vagus fibers. Cyclic AMP in the SCG was also increased about 4- to 5.5-fold over the control within 10 min with the addition of ACh, norepinephrine (NE; 0.05 mM), or high [K+]0. Although NE caused a small increase in cyclic AMP, neither ACh nor high [K+]0 produced any appreciable change in nodose ganglia or vagus fibers. The ODC activity in the SCG was increased by preganglionic stimulation of 3- to 4-hr duration but not by a shorter period. A similar change in ODC activity was caused by the addition of oxotremorine (1 mM), isoproterenol (0.1 mM), NE, cyclic AMP (1 mM), or dibutyryl cyclic GMP (1 mM). The effect was exaggerated by the further addition of 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor. The increase in ODC activity caused by ACh was abolished by a muscarinic cholinergic antagonist, atropine (0.01 mM), and following axotomy for a week, but not by a nicotinic antagonist or by denervation in the SCG. A similar increase in ganglionic ODC activity by NE was inhibited by an adrenergic blocker, propranolol (0.01 mM), and following axtotomy for a week, but not by denervation. Cholinergic or adrenergic stimulation did not cause an increase in ODC activity in nodose ganglia or vagus fibers. These results suggest that the stimulation-induced increase in ODC activity occurs in postganglionic neurons rather than in satellite glial cells and is mediated by muscarinic cholinergic or adrenergic receptors. The process appears to involve cyclic nucleotide-mediated protein biosynthesis in the SCG.     

Tetrahydrobiopterin Turnover in Cultured Rat Sympathetic Neurons: Developmental Profile, Pharmacologic Sensitivity, and Relationship to Norepinephrine Synthesis

We have examined the turnover of 5,6,7,8-tetrahydrobiopterin (BH4) and the effect of decreasing BH4 levels on in situ tyrosine hydroxylase (TH) activity and norepinephrine (NE) content in a homogeneous population of NE-containing neurons derived from the superior cervical ganglion (SCG) of the neonatal rat and maintained in tissue culture. Initial studies indicated that the level of BH4 within SCG cultures increased fourfold between 5 and 37 days in vitro (DIV). This increase in BH4 levels was determined to result from an increase in the rate of BH4 biosynthesis without a change in the rate of degradation. Regardless of culture age, the BH4 content of SCG neurons was observed to turn over with a half-life of approximately 2.5 h. BH4 synthesis by SCG neurons was found to be five times more sensitive to inhibition by 2,4-diamino-6-hydroxypyrimidine (DAHP) and 25 times less sensitive to inhibition by N-acetylserotonin than was previously reported for CNS neurons in culture. Under basal conditions, the rates of in situ TH activity and BH4 biosynthesis were similar. In response to inhibition of BH4 biosynthesis by DAHP and a 90-95% decrease in BH4 levels, in situ TH activity declined by 75%. NE levels declined by 30% following a 24-h period of inhibition of BH4 synthesis. After 2 days of BH4 synthesis inhibition, the level of NE was decreased by 47%. On treatment days 3 and 4, the decline in NE content plateaued at 24% of control levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparative and quantitative study of small intensely fluorescent (SIF) cells in the sympathetic ganglia of some small mammals

This comparative study of the number of SIF cells in the ganglions of the rat, cat, rabbit, mouse and hamster has confirmed that the mean number of SIF cells in the same ganglion of different species varies greatly, for instance in the superior cervical ganglion (SCG) of the rat and the cat, in the stellate ganglion of the cat and the mouse, or in the inferior mesenteric ganglion of the hamster and the other species. There is also considerable variability among individuals of the same animal species. In the SCG, the only ganglion for which there are data on the number of neurons, the ratio of SIF cells to neurons is around 1% in the rat, 0.2% in the rabbit, 0.3% in the mouse and 0.05% in the cat, i.e. a twenty-fold difference between the cat and the rat. Williams et al. (1975) distinguished type 1 SIF cells, corresponding to interneurons, from type 2, which are purely endocrine cells. Type 2 appears to be predominant in all ganglia, except the rabbit SCG where type 1 is highly predominant, and in all species, except the rat, in which this distinction is not applicable. The possible implications of these data on ganglionic functioning are discussed.     

Calcium-related abnormalities in fast and slow denervated skeletal muscle in rats

Muscle weights, Ca-ATPase activity and calcium-binding proteins were studied after denervation in rat extensor digitorum longus (EDL) and soleus (Sol) muscles. Muscle weights decreased progressively as a function of denervation time: after 28 days EDL weight diminished by 70% and Sol weight by 47%. Ca-ATPase activity and calsequestrin were quite reduced in control Sol as compared to the control EDL. Denervation caused a considerable reduction in Ca-ATPase and calsequestrin in EDL, making it resemble the control Sol.     

Neurofilament-like and glial fibrillary acidic protein-like immunoreactivities in rat and guinea-pig sympathetic ganglia in situ and after perturbation

Summary The presence of neurofilament (NF)-like and glial fibrillary acidic protein (GFAP)-like immunoreactivities was studied in sympathetic ganglia of adult rats and guinea pigs during normal conditions and after perturbation. In the superior cervical ganglion (SCG) of normal rats, many ganglion cells and nerve fibers show NF immunoreactivity. Some of these nerve fibers disappear after preganglionic decentralization of SCG; this indicates the presence of a mixture of preand postganglionic NF-positive nerves in the ganglion. Cuts in both preand postganglionic nerves result in a marked increase in GFAP immunoreactivity in SCG, whereas NF immunoreactivity increases in nerve cell bodies after preganglionic cuts. Only a few ganglion cells show NF immunoreactivity in the normal SCG of guinea pig. All intraganglionic NF-positive nerves are of preganglionic origin; decentralization abolishes NF immunoreactivity in these nerve fibers. The inferior mesenteric ganglion, the hypogastric nerves and colonic nerves in guinea pigs contain large numbers of strongly NF-immunoreactive nerve fibers.When the SCG of adult rat is grafted to the anterior eye chamber of adult rat recipients, both ganglionic cell bodies and nerve fibers, forming on the host iris from the grafted ganglion, are NF-positive. As only the perikarya of these neurons normally exhibit NF immunoreactivity, and the terminal iris arborizations are NF-negative, it appears that the grafting procedure causes NF immunoreactivity to become more widespread in growing SCG neurons.     

Neuronal nicotinic acetylcholine receptor alpha3 subunit protein in rat brain and sympathetic ganglion measured using a subunit-specific antibody: regional and ontogenic expression

A synthetic peptide corresponding to the C-terminus of the alpha 3 subunit of the rat neuronal nicotinic acetylcholine receptor (nAChR) was used to generate a rabbit polyclonal alpha 3 antibody. The specificity of this antibody was characterized by immunoblotting, immunohistochemical and immunoprecipitation techniques. Using this antibody, the relative densities of the alpha 3 subunit were quantitatively determined in different brain regions and in superior cervical ganglion (SCG). Among these regions, SCG, interpeduncular nucleus (IPN) and pineal gland showed the highest levels of alpha 3 protein expression. Habenula and superior colliculi had intermediate levels of expression. Low levels were found in cerebral cortex, hippocampus and cerebellum. The ontogenic profile of the alpha 3 subunit in the SCG was also determined. The alpha 3 protein level is low at postnatal day (P 1), but increases rapidly during the first seven postnatal days. This level then plateaus and remains stable through postnatal day 35. These findings suggest that neuronal nAChRs containing the alpha 3 subunit participate in important roles in specific regions of the rat brain and the SCG.     

Alterations in γ-aminobutyric acid content in the rat superior cervical ganglion and pineal gland

The endogenous γ-aminobutyric acid (GABA) content of the rat pineal gland and superior cervical ganglion (SCG) was measured by high pressure liquid chromatography. It was found that GABA levels in both tissues increased after decapitation of the animals. The GABA content of tissues frozen within 20 seconds after decapitation was the same as that of tissues removed from animals killed by microwave irradiation. Amino-oxyacetic acid, a GABA-transaminase inhibitor, increased the endogenous GABA content of both of these tissues. Dimethylphenylpiperizinium or isoniazid administration did not alter GABA levels in these tissues. Isoproterenol increased the GABA content of the SCG but did not change the pineal gland GABA levels. The ability of the pineal gland to take up and accumulate ³H-GABA was significantly reduced in rats that had been ganglionectomized. A fluctuation in endogenous GABA levels in the pineal gland was seen to occur when measures were taken at different times of the day. These results tend to suggest that GABA may have some functional role in the pineal gland and the superior cervical ganglion.     

Calcium-Dependent Transglutaminase of Rat Sympathetic Ganglion in Development and After Nerve Injury

The activity of transglutaminase (TG) was examined in the rat superior cervical ganglion (SCG) during development and after postganglionic nerve crush. During postnatal development the enzyme activity is increased by sevenfold in parallel to protein content of the ganglion and reaches adult levels by day 35 after birth. The endogenous activity (enzyme activity assayed in the absence of the exogenous substrate) during development is transiently elevated with a peak at day 21 postnatal. In the adult ganglion the enzyme specific activity is evenly distributed in all subcellular compartments, but most of it is contained in the cytosol. Within the first hour after axotomy TG activity is rapidly and transiently elevated. The peak value, 80% above control levels, is attained by 30 min postoperative. At this time the activity is increased in all subcellular fractions, but the endogenous activity is selectively increased in the fraction containing nuclei. The enhanced TG activity after axotomy can be prevented by topical treatments with verapamil, an inhibitor of voltage-dependent calcium fluxes across excitable membranes, or with the calcium chelator EGTA. The results show that intracellular TG activity is present in the SCG and that it increases with postnatal growth of the ganglion. After axotomy the enzyme activity is rapidly and transiently increased in the ganglion and this elevation critically depends on calcium fluxes.     

ACETYLCHOLINESTERASE OF RAT SYMPATHETIC GANGLION: MOLECULAR FORMS, LOCALIZATION AND EFFECTS OF DENERVATION

Abstract— In sucrose gradient centrifugation, acetylcholinesterase (AChE, EC 3.1.1.7.) from the rat superior cervical ganglion (SCG) has been found to contain four molecular forms, characterized by their sedimentation coefficients (4 S, 6.5 S, 10 S and 16 S). Homogenization of the ganglia in various media showed that the 4 S enzyme was readily solubilized in water whereas solubilization of the 6.5 S and 10 S forms was quantitative only in media containing Triton X-100. In order to solubilize the 16 S form, high concentrations of salt (NaCl 1 M) and detergent had to be present. AChE analysed by non-denaturing polyacrylamide gel electrophoresis separated into five bands. Although both distribution patterns were stable, i.e. each form or band preserved its characteristic sedimentation or electrophoretic migration when reanalysed, there was no 1:1 correlation between the forms isolated by sedimentation and the bands obtained by electrophoresis: one band might contain more than one form of enzyme, and conversely one form gave rise to several bands. It was therefore impossible to derive molecular weights from electrophoretic migration in non-denaturing gels. However, it could be shown that the results obtained by both methods of analysis were consistent. Acetylcholinesterase from other nervous structures was analysed: in pre- and postganglionic nerves, the main forms were 10 S and 6.5 S, with a small proportion of 4 S; the 16 S form was not detected. In other sympathetic ganglia, the distribution of forms was identical to that of the superior cervical ganglion. In rachidian ganglia, no 16 S form could be found. Following the section of the preganglionic nerve, the acetylcholinesterase activity of the superior cervical ganglion decreased by 50% in 3 days, and then rose again to about 80% of its original value after 2 weeks. These effects mainly reflected variations in the major 4 S and 10 S forms. The 16 S form, in contrast to its disappearance from denervated muscles, increased transiently during the first 2 weeks after denervation, reaching about twice its original activity. A concomitant cytochemical study of normal and denervated ganglia showed that after preganglionic denervation, AChE localized in the sympathetic neurones decreased markedly and remained low even during the recovery phase. During this period a cholinesterasic activity appeared in the perineuronal glia. Controls established that the enzyme synthetized in the glia is AChE.     

ACETYLCHOLINE RECEPTORS: NUMBER and DISTRIBUTION IN INTACT and DEAFFERENTED SUPERIOR CERVICAL GANGLION OF THE RAT1

Abstract— α-Bungarotoxin (α-BuTX) has been used as a marker for studying the acetylcholine receptors (AChRs) in the superior cervical ganglion (SCG) of the adult rat. Binding of [¹²⁵I]α-BuTX to detergent-solubilized AChRs from rat SCG is a saturable and practically irreversible process. The rate constant of association of the toxin-receptor complex is 1.66 × 10⁵M ^?1 S^?1. The receptor is of nicotinic type. One SCG of adult rat binds about 57 fmol of [¹²⁵I]α-BuTX corresponding to 9.2 × 10⁵ AChRs per sympathetic neuron. Light microscope autoradiography shows that AChRs are mainly localized along neuronal processes (probably dendrites). The perikarya exhibit a weak radioactive reaction, while the nerve fibres are devoid of AChRs. Following preganglionic denervation the number of AChRs never increases and their spatial distribution seems not to change.     

Microvascularization of the rat superior cervical ganglion. A three-dimensional observation.

The three-dimensional image of the microvascularization of the rat superior cervical ganglion (SCG) was examined using the vascular corrosion cast technique in conjunction with scanning electron microscopy. It was found that the rat SCG was a highly vascularized organ. Arteries supplying the ganglion gave rise to a subcapsular capillary plexus before branching off to become intraganglionic capillaries. Two types of intraganglionic capillaries, large and small, were observed throughout the organ. Numerous anastomoses among these capillaries were found before they converged into venules and collecting veins. However, a pattern of blood vessels resembling portal-like intraganglionic microcirculation could not be demonstrated.