Neuropeptide distribution in the cervico-thoracic paravertebral ganglia of the cat with particular reference to calcitonin gene-related peptide immunoreactivity

Summary Paraffin sections of cervical and upper thoracic paravertebral ganglia of the cat were investigated by immunohistochemistry using antisera directed against calcitonin gene-related peptide (CGRP). The relationships of CGRP-immunoreactive structures to those exhibiting immunoreactivity to antisera against other regulatory peptides and dopamine--hydroxylase (DBH), respectively, were studied in consecutive sections. Singly scattered CGRP-immunoreactive neuronal perikarya were observed in the superior and middle cervical ganglia as well as in the stellate ganglion. These neurons also displayed immunoreactivity to vasoactive intestinal polypeptide (VIP), and some additionally exhibited faint substance-P immunoreactivity. DBH- and neuropeptide Y-immunoreactive ganglion cells were not identical with CGRP-immunoreactive neuronal cell bodies.According to the immunoreactive properties of varicosities, which abut on CGRP/VIP-immunoreactive perikarya, three types of CGRP/VIP-immunoreactive ganglion cells could be distinguished: (1) CGRP/VIP-immunoreactive neurons being surrounded by somatostatin-immunoreactive nerve fibers, (2) neurons being approached by both DBH- and met-enkephalin-immunoreactive varicosities, and (3) neurons receiving both DBH- and neurotensin-immunoreactive fibers. The stellate and upper thoracic ganglia harbored clusters of intensely VIP-immunoreactive somata, which lacked CGRP-immunoreactivity. Fine somatostatin-immunoreactive and coarse CGRP-immunoreactive fibers were distributed within these clusters, whereas patches of neurotensin-immunoreactive fibers were complementarily arranged. At all segmental levels investigated, a few postganglionic neurons were approached by both CGRP-immunoreactive and substance P-immunoreactive varicosities, but lacked a VIP-immunoreactive innervation. Therefore, CGRP/substance P-immunoreactive fiber baskets appeared rather to be of extraganglionic origin than to emerge from intraganglionic CGRP/VIP/SP neurons. CGRP-immunoreactive cell bodies or fibers were absent in clusters of small paraganglionic cells, but some of the solitary paraganglionic cells displayed CGRP-immunoreactivity. Our findings establish the presence of CGRP-immunoreactivity in a population of sympathetic neurons in the cat. A highly differentiated, segment-dependent organizational pattern of neuropeptides in cervico-thoracic paravertebral ganglia was demonstrated.Supported by Deutsche Forschungsgemeinschaft grant He 919/6-2     

Ionic channels and conductance-based models for hypothalamic neuronal thermosensitivity

Thermoregulatory responses are partially controlled by the preoptic area and anterior hypothalamus (PO/AH), which contains a mixed population of temperature-sensitive and insensitive neurons. Immunohistochemical procedures identified the extent of various ionic channels in rat PO/AH neurons. These included pacemaker current channels [i.e., hyperpolarization-activated cyclic nucleotide-gated channels (HCN)], background potassium leak channels (TASK-1 and TRAAK), and transient receptor potential channel (TRP) TRPV4. PO/AH neurons showed dense TASK-1 and HCN-2 immunoreactivity and moderate TRAAK and HCN-4 immunoreactivity. In contrast, the neuronal cell bodies did not label for TRPV4, but instead, punctate labeling was observed in traversing axons or their terminal endings. On the basis of these results and previous electrophysiological studies, Hodgkin-Huxley-like models were constructed. These models suggest that most PO/AH neurons have the same types of ionic channels, but different levels of channel expression can explain the inherent properties of the various types of temperature-sensitive and insensitive neurons.     

Horseradish peroxidase localization of sympathetic postganglionic and parasympathetic preganglionic neurons innervating the monkey heart

The localization of the sympathetic postganglionic and parasympathetic preganglionic neurons innervating the monkey heart were investigated through retrograde axonal transport with horseradish peroxidase (HRP). HRP (4 mg or 30 mg) was injected into the subepicardial and myocardial layers in four different cardiac regions. The animals were euthanized 84-96 hours later and fixed by paraformaldehyde perfusion via the left ventricle. The brain stem and the paravertebral sympathetic ganglia from the superior cervical, middle cervical, and stellate ganglia down to the T9 ganglia were removed and processed for HRP identification. Following injection of HRP into the apex of the heart, the sinoatrial nodal region, or the right ventricle, HRP-labeled sympathetic neurons were found exclusively in the right superior cervical ganglion (64.8%) or in the left superior cervical ganglion (35%). Fewer labeled cells were found in the right stellate ganglia. After HRP injection into the left ventricle, labeled sympathetic cells were found chiefly in the left superior cervical ganglion (51%) or in the right superior cervical ganglion (38.6%); a few labeled cells were seen in the stellate ganglion bilaterally and in the left middle cervical ganglion. Also, in response to administration of HRP into the anterior part of the apex, anterior middle part of the right ventricle, posterior upper part of the left ventricle, or sinoatrial nodal region, HRP-labeled parasympathetic neurons were found in the nucleus ambiguus on both the right (74.8%) and left (25.2%) sides. No HRP-labeled cells were found in the dorsal motor nucleus of the vagus on either side.     

FRS2 alpha 2F/2F mice lack carotid body and exhibit abnormalities of the superior cervical sympathetic ganglion and carotid sinus nerve

The docking protein FRS2α is an important mediator of fibroblast growth factor (FGF)-induced signal transduction, and functions by linking FGF receptors (FGFRs) to a variety of intracellular signaling pathways. We show that the carotid body is absent in FRS2α^2F/2F mice, in which the Shp2-binding sites of FRS2α are disrupted. We also show that the carotid body rudiment is not formed in the wall of the third arch artery in mutant embryos. In wild-type mice, the superior cervical ganglion of the sympathetic trunk connects to the carotid body in the carotid bifurcation region, and extends thick nerve bundles into the carotid body. In FRS2α^2F/2F mice, the superior cervical ganglion was present in the lower cervical region as an elongated feature, but failed to undergo cranio-ventral migration. In addition, few neuronal processes extended from the ganglion into the carotid bifurcation region. The number of carotid sinus nerve fibers that reached the carotid bifurcation region was markedly decreased, and baroreceptor fibers belonging to the glossopharyngeal nerve were absent from the basal part of the internal carotid artery in FRS2α^2F/2F mutant mice. In some of the mutant mice (5 out of 14), baroreceptors and some glomus cells were distributed in the wall of the common carotid artery, onto which the sympathetic ganglion abutted. We propose that the sympathetic ganglion provides glomus cell precursors into the third arch artery derivative in the presence of sensory fibers of the glossopharyngeal nerve.     

Mash1 is required for glomus cell formation in the mouse carotid body

The carotid body consists of chemoreceptive glomus cells, sustentacular cells and nerve endings. The murine carotid body, located at the carotid bifurcation, is always joined to the superior cervical ganglion of the sympathetic trunk. Glomus cells and sympathetic neurons are immunoreactive for the TuJ1, PGP9.5, tyrosine hydroxylase (TH) and neuropeptide Y (NPY) markers. Glomus cells are also immunoreactive for serotonin (5-HT). A targeted mutation of Mash1, a mouse homolog of the Drosophila achaete-scute complex, results in the elimination of sympathetic ganglia. In Mash1 null mutant mice, the carotid body primordium forms normally in the wall of the third arch artery at embryonic day (E) 13.0 and continues to develop, although the superior cervical ganglion is completely absent. However, no cells in the mutant carotid body display the TuJ1, PGP 9.5, TH, NPY and 5-HT markers throughout development. The absence of glomus cells was also confirmed by electron microscopy. The carotid body of newborn null mutants is composed of mesenchymal-like cells and nerve fibers. Many cells immunoreactive for the S-100 protein, a sustentacular cell marker, appear in the mutant carotid body during fetal development. The Mash1 gene is thus required for the genesis of glomus cells but not for sustentacular cells.     

Changes in TWIK-related Acid Sensitive K+-1 and -3 Channel Expressions from Neurons to Glia in the Hippocampus of Temporal Lobe Epilepsy Patients and Experimental Animal Model

In the present study, we analyzed expressions of tandem of P domains in a Weak Inwardly rectifying K⁺ channel (TWIK)-related Acid-Sensitive K⁺ (TASK) channel-1 and -3 in the hippocampus of patients with temporal lobe epilepsy (TLE) and in rat model. In the control human subjects, TASK-1, and -3 immunoreactivity was observed in pyramidal neurons and dentate granule cells. In TLE patients, TASK-1 and -3 immunoreactivity was rarely observed in neurons. However, TASK-1 immunoreactivity was observed in astrocytes, and TASK-3 immunoreactivity was detected in both astrocytes and microglia. In the rat hippocampus, TASK-1 immunoreactivity was observed in astrocytes within normal and epileptic hippocampus. The alterations in TASK-3 immunoreactivity in the rat hippocampus were similar to those in the human hippocampus. These findings reveal that TASK-1 and -3 are differentially expressed in the normal and epileptic hippocampus, and suggest that TASK channels may contribute to the properties of the epileptic hippocampus.     

Met5-enkephalin-Arg6-Gly7-Leu8-immunoreactive nerve fibers in the major salivary glands of the rat: evidence for both sympathetic and parasympathetic origin

Summary The localization of the proenkephalin A-derived octapeptide, Met⁵-enkephalin-Arg⁶-Gly⁷-Leu⁸ (MEAGL), was studied in the major salivary glands of Sprague-Dawley and Wistar rats with the indirect immunofluorescence method. MEAGL-immunoreactive nerve fibers were found around the acini, along intra-and interlobular salivary ducts and in close contact with blood vessels. In the parotid and submandibular glands tyrosine hydroxylase (TH) immunoreactivity was observed in nerve fibers around the acini, in association with intra- and interlobular salivary ducts and around blood vessels, while in the sublingual gland TH-immunoreactive nerve fibers were only seen around blood vessels. Parasympathetic neurons in submandibular ganglia contained MEAGL immunoreactivity. Moderate TH immunoreactivity was seen in some neurons of the submandibular ganglia. A subpopulation of sympathetic principal neurons in the superior cervical ganglion were immunoreactive for both MEAGL and TH. In the trigeminal ganglion, no MEAGL-immunoreactive sensory neurons or nerve fibers were observed. Superior cervical ganglionectomies resulted in a complete disappearance of TH-immunoreactive nerve fibers, while MEAGL-immunoreative nerve fibers were still present in the glands. The presence of MEAGL immunoreactivity in neurons of both sympathetic superior cervical ganglia and parasympathetic submandibular ganglia and the results of superior cervical ganglionectomies suggest, that MEAGL-immunoreactive nerve fibers in the major salivary glands of the rat have both sympathetic and parasympathetic origin.     

KISS1 and KISS1R expression in the human and rat carotid body and superior cervical ganglion

KISS1 and its receptor, KISS1R, have both been found to be expressed in central nervous system, but few data are present in the literature about their distribution in peripheral nervous structures. Thus, the aim of the present study was to investigate, through immunohistochemistry, the expression and distribution of KISS1 and KISS1R in the rat and human carotid bodies and superior cervical ganglia, also with particular reference to the different cellular populations. Materials consisted of carotid bodies and superior cervical ganglia were obtained at autopsy from 10 adult subjects and sampled from 10 adult Sprague-Dawley rats. Immunohistochemistry revealed diffuse expression of KISS1 and KISS1R in type I cells of both human and rat carotid bodies, whereas type II cells were negative. In both human and rat superior cervical ganglia positive anti-KISS1 and -KISS1R immunostainings were also selectively found in ganglion cells, satellite cells being negative. Endothelial cells also showed moderate immunostaining for both KISS1 and KISS1R. The expression of both kisspeptins and kisspeptin receptors in glomic type I cells and sympathetic ganglion cells supports a modulatory role of KISS1 on peripheral chemoreception and sympathetic function. Moreover, local changes in blood flow have been considered to be involved in carotid body chemoreceptor discharge and kisspeptins and kisspeptin receptors have also been found in the endothelial cells. As a consequence, a possible role of kisspeptins in the regulation of carotid body blood flow and, indirectly, in chemoreceptor discharge may also be hypothesized.     

Sympathetic innervation of the carotid bifurcation in the rabbit and cat: Blood vessels,carotid body and carotid sinus

Summary Two postganglionic branches of the superior cervical ganglion enter the area of the carotid bifurcation in the rabbit and the cat. The common and external carotid arteries receive a rich adrenergic nerve supply, which can be demonstrated by fluorophores of biogenic amines appearing after formaldehyde treatment. The internal carotid artery is only sparsely innervated; however, it shows a dense sympathetic supply at the site of pressor receptors. Following removal of the superior cervical ganglion, a total loss of fluorescent adrenergic nerves occurs and degeneration of nerve endings possessing dense core vesicles is conspicuous. These nerve terminals are situated mainly subendothelially in the carotid body sinusoids; they only rarely terminate on type I cells.     

Histochemically demonstrable catecholamines in sympathetic ganglia and carotid body of spontaneously hypertensive and normotensive rats

Summary The catecholamine content and morphology of the superior cervical and the hypogastric ganglion and the carotid body were studied in Spontaneously Hypertensive Rats (SHR) before (at the age of 6 weeks) and after (at the age of 20 weeks) becoming hypertensive, with Wistar Kyoto (WKY) rats as controls. The study was performed by formaldehyde-induced fluorescence method combined with quantitative microfluorimetry of catecholamines.At the age of 6 weeks the only significant difference observed between the rat strains was a greater number of small intensely fluorescent (SIF) cells in the superior cervical ganglion of SHR. At the age of 20 weeks the fluorescence intensity was higher in the principal neurons of the superior cervical ganglion and in glomus cells of the carotid body of SHR compared to WKY. The volumes of superior cervical ganglion and carotid body were larger in 20-week-old SHR compared to WKY. In the hypogastric ganglion differences were not found between SHR and WKY rats. The present results show differences in the superior cervical ganglion and in the carotid body of adult SHR compared to controls. These differences develop during the time period when the SHR become hypertensive, and might be functionally significant in the regulation or maintenance of the increased blood pressure in SHR rats.     

Histochemically demonstrable catecholamines in sympathetic ganglia and carotid body of spontaneously hypertensive and normotensive rats

The catecholamine content and morphology of the superior cervical and the hypogastric ganglion and the carotid body were studied in Spontaneously Hypertensive Rats (SHR) before (at the age of 6 weeks) and after (at the age of 20 weeks) becoming hypertensive, with Wistar Kyoto (WKY) rats as controls. The study was performed by formaldehyde-induced fluorescence method combined with quantitative microfluorimetry of catecholamines. At the age of 6 weeks the only significant difference observed between the rat strains was a greater number of small intensely fluorescent (SIF) cells in the superior cervical ganglion of SHR. At the age of 20 weeks the fluorescence intensity was higher in the principal neurons of the superior cervical ganglion and in glomus cells of the carotid body of SHR compared to WKY. The volumes of superior cervical ganglion and carotid body were larger in 20-week-old SHR compared to WKY. In the hypogastric ganglion differences were not found between SHR and WKY rats. The present results show differences in the superior cervical ganglion and in the carotid body of adult SHR compared to controls. These differences develop during the time period when the SHR become hypertensive, and might be functionally significant in the regulation or maintenance of the increased blood pressure in SHR rats.     

Homeobox gene hoxa3 is essential for the formation of the carotid body in the mouse embryos

Homeobox gene Hoxa3 is strongly expressed in the third pharyngeal arch and pouch. We found that Hoxa3 homozygous null mutant mice had the lack of the carotid body. In all late-term mutant embryos examined (n = 10), no carotid body was present. The carotid body rudiment is formed in the wall of the third branchial artery, which develops into the common carotid artery and the first part of the internal carotid artery. The symmetrical patterns of the third, fourth, and sixth arch arteries were observed in wild-type littermates at embryonic day (E) 10.5-12.5. In Hoxa3 homozygous mutant embryos, however, the third arch artery began to degenerate at E10.5 and almost disappeared at E11.5. Furthermore, the bifurcation of the common carotid artery at the normal position, i.e., at the upper end of the larynx, was never detected in the mutant embryos at E16.5-E18.5. The common carotid artery of the homozygous mutants was separated into the internal and external carotid arteries immediately after its origin. Thus, the present study evidenced that the absence of the carotid body in Hoxa3 homozygous mutants is due to the defect of development of the third arch artery, resulting in malformation of the carotid artery system. During fetal development, the carotid body of mice is in close association with the superior cervical ganglion of the sympathetic trunk. The superior cervical ganglion rather showed hypertrophic features in Hoxa3 homozygous mutants lacking the carotid body.     

Immunohistochemical and histochemical evidence for the presence of noradrenaline,serotonin and gamma-aminobutyric acid in chief cells of the mouse carotid body

The immunohistochemical study revealed tyrosine hydroxylase (TH), dopamine -hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), serotonin, glutamate decarboxylase (GAD) and -aminobutyric acid (GABA) immunoreactivities in the mouse carotid body. TH and DBH immunoreactivities were found in almost all chief cells and a few ganglion cells, and in relatively numerous varicose nerve fibers of the carotid body. The histofluorescence microscopy showed catecholamine fluorescence in almost all chief cells. However, no PNMT immunoreactivity was observed in the carotid body. Serotonin, GAD and GABA immunoreactivities were also seen in almost all chief cells of the carotid body. From combined immunohistochemistry and fluorescence histochemistry, catecholamine and serotonin or catecholamine and GABA were colocalized in almost all chief cells. Thus, these findings suggest that noradrenaline, serotonin and GABA may be synthesized and co-exist in almost all chief cells of the mouse carotid body and may play roles in chemoreceptive functions.     

Immunohistochemical evidence for different pathways immunoreactive to substance P and calcitonin gene-related peptide (CGRP) in the guinea-pig stellate ganglion

The colocalization of immunoreactivities to substance P and calcitonin gene-related peptide (CGRP) in nervous structures and their correlation with other peptidergic structures were studied in the stellate ganglion of the guinea pig by the application of double-labelling immunofluorescence. Three types of fibre were distinguished. (1) Substance P⁺/CGRP⁺ fibres, which sometimes displayed additional immunoreactivity for enkephalin, constituted a small fibre population of sensory origin, as deduced from retrograde labelling of substance P⁺/CGRP⁺ dorsal root ganglion cells. (2) Substance P⁺/CGRP^– fibres were more frequent; some formed baskets around non-catecholaminergic perikarya that were immunoreactive to vasoactive intestinal polypeptide (VIP). (3) CGRP⁺/substance P^– fibres were most frequent and were mainly distributed among tyrosine hydroxylase (TH)-immunoreactive cell bodies. The peptide content of fibre populations (2) and (3) did not correspond to that of sensory ganglion cells retrogradely labelled by tracer injection into the stellate ganglion. Therefore, these fibres are throught to arise from retrogradely labelled preganglionic sympathetic neurons of the spinal cord, in which transmitter levels may have been too low for immunohistochemical detection of substance P or CGRP. CGRP-immunoreactivity but no substance P-immunolabelling was observed in VIP-immunoreactive postganglionic neurons. Such cell bodies were TH-negative and were spared by substance P-immunolabelled fibre baskets. Retrograde tracing with Fast Blue indicated that the sweat glands in the glabrous skin of the forepaw were the targets of these neurons. The streptavidin-biotin-peroxidase method at the electron-microscope level demonstrated that immunoreactivity to substance P and CGRP was present in dense-cored vesicles of 50–130 nm diameter in varicosities of non-myelinated nerve fibres in the stellate ganglion. No statistically significant difference in size was observed between vesicles immunolabelled for substance P and CGRP. Immunoreactive varicosities formed axodendritic and axosomatic synaptic contacts, and unspecialized appositions to non-reactive neuronal dendrites, somata, and axon terminals. Many varicosities were partly exposed to the interstitial space. The findings provide evidence for different pathways utilizing substance P and/or CGRP in the guinea-pig stellate ganglion.     

Autoradiographic study of 3H-lysine uptake by superior cervical and stellate ganglia in prehypertensive spontaneously hypertensive rats

In order to compare the functional state of sympathetic ganglia in spontaneously hypertensive (SHR) with those in normotensive Wistar Kyoto rats (WKY), protein synthetic activity was examined by light microscopic autoradiography with 3H-lysine. The number of silver grains over the cytoplasm of ganglion cells in the superior cervical and stellate ganglia of newborn and 30-day-old animals were counted on photographic enlargements. In both sympathetic ganglia there were significantly more silver grains over ganglion cells in SHR compared with age-matched WKY at 15, 60, and 120 min after injection of 3H-lysine. The increased incorporation of the label by both sympathetic ganglia was more marked in newborn than in 30-day-old animals. This result shows that protein synthetic activity in these ganglion cells is increased in SHR from the newborn stage. It is suggested that a congenital hyperfunction of sympathetic ganglia occurs in SHR.     

Phenotypic alterations of neuropeptide Y and calcitonin gene-related peptide-containing neurons innervating the rat temporomandibular joint during carrageenan-induced arthritis

The aim of this study was to identify immunoreactive neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) neurons in the autonomic and sensory ganglia, specifically neurons that innervate the rat temporomandibular joint (TMJ). A possible variation between the percentages of these neurons in acute and chronic phases of carrageenan-induced arthritis was examined. Retrograde neuronal tracing was combined with indirect immunofluorescence to identify NPY-immunoreactive (NPY-IR) and CGRP- immunoreactive (CGRP-IR) neurons that send nerve fibers to the normal and arthritic temporomandibular joint. In normal joints, NPY-IR neurons constitute 78±3%, 77±6% and 10±4% of double-labeled nucleated neuronal profile originated from the superior cervical, stellate and otic ganglia, respectively. These percentages in the sympathetic ganglia were significantly decreased in acute (58±2% for superior cervical ganglion and 58±8% for stellate ganglion) and chronic (60±2% for superior cervical ganglion and 59±15% for stellate ganglion) phases of arthritis, while in the otic ganglion these percentages were significantly increased to 19±5% and 13±3%, respectively. In the trigeminal ganglion, CGRP-IR neurons innervating the joint significantly increased from 31±3% in normal animals to 54±2% and 49±3% in the acute and chronic phases of arthritis, respectively. It can be concluded that NPY neurons that send nerve fibers to the rat temporomandibular joint are located mainly in the superior cervical, stellate and otic ganglia. Acute and chronic phases of carrageenan-induced arthritis lead to an increase in the percentage of NPY-IR parasympathetic and CGRP-IR sensory neurons and to a decrease in the percentage of NPY-IR sympathetic neurons related to TMJ innervation.Key words: trigeminal ganglion, otic ganglion, superior cervical ganglion, arthritis, temporomandibular joint.     

New synapses associated with the granule-containing cells of rat sympathetic ganglia

The synapses of the rat superior cervical sympathetic ganglion were studied with both conventional and ultrastructural histochemical methods. Besides the cholinergic synapses polarized from preganglionic fibers to sympathetic ganglion neurons, two morphologically and functionally different types of synapses were observed in relation to the small granule-containing (catecholamine-containing) cells of the rat superior cervical ganglion. The first type is an efferent adrenergic synapse polarized from granule-containing cells to the dendrites of the sympathetic ganglion neurons. This type of synapse might mediate the inhibitory effects (slow inhibitory postsynaptic potentials) induced by catecholamines on the sympathetic neurons. The second type is a reciprocal type of synapse between the granule-containing cells and the cholinergic preganglionic fibers. Through such synapses, these cells could exert a modulating effect on the excitatory preganglionic fibers. Therefore, we propose that these cells, through their multiple synaptic connections, exhibit a local modulatory feedback system in the rat sympathetic ganglia and may serve as interneurons between the preganglionic and postganglionic sympathetic neurons.     

Acetyl- and pseudocholinesterase activities in sympathetic ganglia of rats

—The quantitative method of Ellman , Courtney , Andres and Featherstone (1961) was adapted to a differential assay for the determination of acetyl- and pseudocholinesterase activities of sympathetic ganglia of rats. The activities of the cholinesterases of superior cervical, stellate and thoracic chain ganglia and of the abdominal ganglionic complexes in apposition to the superior mesenteric and coeliac arteries (superior mesenteric, coeliac and cardiac ganglia) were measured. B.W.284C51 dibromide, 5 × 10^?5m , and ethopropazine hydrochloride, 3·15 × 10^?5m , were employed to inhibit selectively acetyl- and pseudocholinesterases, respectively. Linearity was shown to be maintained with enzyme concentrations corresponding to 0·12-0·5 mg of ganglion (wet wt.)/incubation. Under the experimental conditions of this assay, the rates of the reaction of ganglionic acetyl- and pseudocholinesterases were linear for time periods greater than those employed for calculating the rates of hydrolysis in the homogenates of sympathetic ganglia. Several experimental approaches were used to ascertain the specificity of the inhibitors and of the reaction. Of the total cholinesterase activity of sympathetic ganglia of rats, 55-63 per cent was due to acetylcholinesterase and 31-39 per cent to pseudocholinesterase. On the basis of the specific enzyme activity, superior cervical, stellate and superior mesenteric ganglia contained higher acetyl- and pseudocholinesterase activities than did thoracic chain, coeliac and cardiac (abdominal) ganglia. The specific activity of acetylcholinesterase was similar in rat and cat superior cervical ganglia and sympathetic cervical trunks while the pseudocholinesterase activity of these two tissues was somewhat lower in cats than in rats.