Morphometric analysis of glomus cells within the recurrent laryngeal nerve of the rat

Summary An endoneurial paraganglion located in the recurrent laryngeal nerve of the rat was found in 17 of 20 nerves studied. The median size of the paraganglia was estimated to be 0.8 × 10⁶ m³. The number of type I like cells within a paraganglion ranged between 8 and 24. Altogether, 120 endoneurial dense-cored vesicle cells from 8 paraganglia were subjected to a morphometric analysis at the ultrastructure level. The mean vesicle profile diameter was estimated to be 101.3 nm and only one type of granulated cell could be distinguished. The volume density of the dense-cored vesicles was estimated to be about 6%, a value amounting to two to three times that in the carotid glomus. Moreover, the mean cell profile area of vesiculated cells of recurrent laryngeal nerve exceeds that of the cells of the carotid glomus.     

Catecholamines of endoneurial laryngeal paraganglia in the rat

The catecholamines in the recurrent and superior laryngeal nerves of the rat were assayed by high performance liquid chromatography. The nerves were shown to contain high levels of dopamine (1.9 ± 0.6 and 2.3 ± 0.4 pmol, respectively) and noradrenaline (1.3 ± 0.3 and 0.9 ± 0.2 pmol, respectively). No adrenaline could be detected in any of the nerves. Reserpine markedly depleted the stores of these amines in both nerves. A significant increase in dopamine level was seen in the superior laryngeal nerve after treatment with a monoaminoxidase inhibitor, but not in the recurrent laryngeal nerve. The high levels of dopamine detected are presumably derived from endoneurial paraganglia which were demonstrated by glyoxylic acid-induced fluorescence. The source of noradrenaline is less evident, but noradrenaline is probably stored in both endoneurial paraganglia and in sympathetic nerve endings.,     

Intact and sympathectomized carotid bodies of long-term hypoxic rats: a morphometric ultrastructural study

Summary The ultrastructure of the carotid body after exposure to hypoxia (10% O₂) for one, two or three weeks was investigated morphometrically. The study was performed on rats after unilateral removal of the superior cervical ganglion. The normally occurring bimodal distribution of type I cells, representing cells with small vesicle profile diameters (SVC) and large vesicle profile diameters (LVC) respectively, changed after one week of hypoxia into a unimodal population. After one or two weeks of hypoxia the diameter range of dense-cored vesicle (DCV) profiles in type I cells was not different from that of DCV profiles in control LVC. After three weeks of hypoxia the DCV vesicle size was intermediate between those of control SVC and LVC. The volume density of DCV decreased after one week but returned to initial values after two and three weeks of hypoxia. At two or three weeks of hypoxia, however, the total cell volume was increased about 1.4 times which should reflect an increase of the total content of DCV at these times of exposure to hypoxia. An increased mean area of cell profiles indicates a hypertrophy of the type I cells, but no signs of hyperplasia could be detected. The ganglionectomy did not cause any remarkable changes compared to the intact carotid body except for a higher volume density of DCV during the early periods of hypoxia.It is inferred from the study that the increased total mass of type I cell tissue during long-term hypoxia is due to a hypertrophy of the cells. Furthermore, the type I cells can increase their storage capacity for catecholamines during hypoxia by an increase in the size and number of DCV.     

The paraganglia within the carotid bifurcation regions of young and old spontaneously hypertensive rats (SHR) after exposure to chronic hypobaric hypoxia. II. The carotid body-like organs

The following paraganglia in the carotid bifurcations regions of spontaneously hypertensive rats (SHR) were studied: Endoneural paraganglia within the external carotid nerve, the carotid sinus nerve, the glossopharyngeal nerve, and the pharyngeal branch of the vagus nerve, the so-called periadventitial type I cells, and so-called miniglomera. Number and distribution of these paraganglia vary among different individuals. After chronically hypobaric hypoxia the volume of these paraganglia was increased but their number remained unchanged. The increase of volume was dependent on the duration of hypoxia. There were no differences between young and old SHR when the hypoxia-time was the same.     

Opioid peptides and noradrenaline co-exist in large dense-cored vesicles from sympathetic nerve

The possibility that opioid peptides and noradrenaline co-exist not only in the desheathed bundle of bovine splenic nerve which contains ~98% sympathetic C-fibers, but also in the population of large dense-cored noradrenergic vesicles from these fibers, has been investigated. The primary fraction of large dense-cored vesicles which can be prepared at about 85% purity has been further subjected to density gradient and fractional centrifugation procedures, including D₂O-loading and unloading on modified second gradients, in an attempt to separate any minor population of particles which potentially could contain opioid peptides and contaminate the large dense-cored vesicle fraction. Measurement of opioid peptides, noradrenaline, dopamine and dopamine β-hydroxylase activity supports the conclusion that opioid peptides are stored in the primary population of large dense-cored vesicles per se, rather than in a minor population of contaminating particles from cells other than sympathetic C-fibers.This conclusion has implications for exocytotic release and the physiological role of the opioid peptides intra- and extra-neuronally. Nerve vesicle opioid peptides have a size less than 5000 daltons, in contrast to the high proportion of large peptides containing enkephalin sequences in the bovine adrenal medulla.     

Expression of catecholamine-synthesizing enzymes in paraganglionic and ganglionic cells in the laryngeal nerves of the rat

Summary The rat recurrent and superior laryngeal nerves with adjacent connective tissue were examined by immunohistochemical techniques for localization of the catecholamine-synthesizing enzymes tyrosine hydroxylase, dopamine--hydroxylase and phenylethanolamine-n-methyltransferase. Most of the cells in the paraganglia of the recurrent and superior laryngeal nerves showed an intense tyrosine hydroxylase-like immunoreactivity. A few paraganglionic cells exhibited dopamine--hydroxylase-like immunoreactivity while none of the cells displayed phenylethanolamine-n-methyltransferase-like immunoreactivity. Some of the ganglionic cells in the recurrent and superior laryngeal nerves showed dopamine--hydroxylase-like immunoreactivity whilst these cells never showed tyrosine hydroxylase- or phenylethanolamine-N-methyltransferase-like immunoreactivity. The arterioles were supplied with plexuses of nerve fibres showing tyrosine hydroxylase- and dopamine--hydroxylase-like immunoreactivity. The results indicate that dopamine is the major catecholamine located in the laryngeal nerve paraganglia and show that ganglionic cells in the recurrent and superior laryngeal nerves show immunolabelling for one of the enzymes in the catecholamine synthetic pathway, dopamine--hydroxylase.     

Evidence that most of the dopamine β-hydroxylase is not membrane bound in purified large dense cored noradrenergic vesicles

The compartmentalization of dopamine β-hydroxylase was studied in a purified fraction of large, dense-cored noradrenergic vesicles from bovine splenic nerve. A correlative biochemical and morphological approach was used to evaluate physical methods designed to produce more efficient vesicle lysis than has been accomplished previously with freeze-thawing, hypo-osmotic shocks or incubation at 37°C, all of which are relatively ineffective. Of the seven purely physical techniques tested, only those which subjected the vesicles to high pressures followed by rapid decompression produced effective lysis, unmasking of latent enzyme activity, and release of enzyme into the soluble phase. Based on results with the French Press, the best estimate for the percentage of dopamine β-hydroxylase which can be released into the soluble phase is 55–70% of the total enzyme activity produced by the addition of 0.05% v/v Triton X-100. This includes two-thirds of the enzyme which was originally in a latent form. The enzyme is considered to occur primarily, if not entirely, in a granular complex in the vesicle matrix. About one-third is thought to be oriented specifically at the inner surface of the vesicle membrane and is active enzymatically.Physical rupture of the vesicles causes redistribution of partially depleted vesicles and free matrix granules containing dopamine β-hydroxylase activity into less dense zones of a sucrose-D₂O density gradient. After French Press treatment, 30% of the enzyme lost from the heavy vesicle peak is found in the region of the light vesicle peak which is thought to be the equilibrium density of the smaller vesicles characteristic of nerve terminals.The data indicate that much more dopamine β-hydroxylase is potentially available for release from the large, dense-cored vesicles upon nerve stimulation than previously has been believed. This will affect interpretations of exocytotic release from the two vesicle populations in noradrenergic varicosities and will have a bearing on the origin of circulating dopamine β-hydroxylase in response to physiological stress and pharmacological intervention, as well as in neurological diseases.     

Ultrastructure of the glomus cells in the carotid body of chronically hypoxic rats: With special reference to the similarity of amphibian glomus cells

The ultrastructural characteristics of the glomus cells in the rat carotid body exposed to extremely long-term hypoxia (10–12 weeks) were investigated. The glomus cells could be classified into four distinct types according to the shape of dense-cored vesicles in the glomus cell cytoplasm: (1) small vesicle cells (SVCs, 50 nm in mean diameter), (2) large vesicle cells (LVCs, 80 nm in mean diameter), (3) dilated eccentric vesicle cells (EVCs, 400–800 nm in diameter), and (4) mixed vesicle cells (MVCs, large and eccentric vesicles). Many clusters of glomus cells were found to contain all four categories of cell types. The appearance of EVCs was a unique and common characteristic of glomus cells in this long-term hypoxia model. We also noted other ultrastructural features with chronic hypoxia which are characteristic of the amphibian carotid labyrinth glomus cells: (1) incomplete covering of glomus cells with the supporting cell missing over a wide area, (2) long thin cytoplasmic projections in the intervascular stroma, and (3) intimate apposition of the glomus cells and pericytes (g-p connection), endothelial cells (g-e connection), plasma cells, and fibrocytes. Because arterial PO₂ is generally low in amphibia, these may be general features of hypoxic adaptation and facilitate both uptake of oxygen from blood and release of catecholamine into the blood. The g-p and g-e connections may take part in the regulation of the microcirculation in the enlarged carotid body. © 1993 Wiley-Liss Inc.     

Effects of 5-hydroxydopamine and 6-hydroxydopamine on the ultrastructure of type I cells in paraganglia of the rat recurrent laryngeal nerve.

The ultrastructure of the Type I cells in paraganglia of rat recurrent laryngeal nerve (RLN) was studied after the administration of 5-hydroxydopamine (5-OHDA) and 6-hydroxydopamine (6-OHDA). Normal Type I cells of RLN-paraganglia contained abundant organelles and their cytoplasm was characterized by the presence of numerous membrane-bounded dense-cored vesicles (DCVs). The DCVs were round in profile (diameter 107.67 +/- 0.06 nm, all values expressed as mean +/- s.e.m. in the present study) and possessed dense cores of moderate to low electron density. After 5-OHDA treatment (single injection, 100 mg/kg b.w., i.v.), the majority of DCVs were filled with a material of high electron density. No significant difference was observed between the profile diameter of the DCVs in 5-OHDA-treated rats (104.96 +/- 0.06 nm) and that in normal rats. After 6-OHDA treatment (three injections, 100 mg/kg b.w. each at 12 h intervals i.p.), no significant alteration in the electron density of the core was noted. However, most of the DCVs were enlarged and round, elliptical or irregular in profile (190.57 +/- 2.77 nm x 130.34 +/- 2.09 nm). The dense core of DCVs was centrally or eccentrically located in DCVs. The results of the present study indicate that: 1) there is only one type of granulated glomus cell (i.e., Type I cells) in the rat RLN-paraganglia under normal physiological condition; and 2) since the ultrastructural morphology of DCVs in Type I cells of rat RLN-paraganglia is altered after 5-OHDA or 6-OHDA treatment, these cells may possess mechanisms for the uptake of false adrenergic neurotransmitter and/or neurotoxin.     

Structural and neurochemical changes in the maturation of the carotid body

Functional maturation of the carotid body in the postnatal period relies partly on structural and neurochemical changes, which are reviewed here. Structural changes include changes in cytological composition, and increases in glomic tissue volume, dense-cored granules of type I cells, synapses of type I cells with type II cells and afferent nerve fibres. Vascular volume also increases, but in the same proportion as extravascular volume. During maturation, the carotid body also shows higher density and hypoxic sensitivity of K⁺-channels and an increased hypoxic [Ca²⁺]_i response. Modulation of content and release of catecholamine occurs, together with decreased expression of tyrosine hydroxylase and dopamine β-hydroxylase and increased expression of choline acetyltransferase. Expression of dopamine 2 receptor and nicotinic α3 and α7 receptor subunits increases, and muscarinic M1 receptor protein, nicotinic α4 and β2 receptor subunits and adenosine receptor 1 decrease. Maturation of the carotid body may also be explained with reference to the developmentally regulated expression of trophic factors and their receptors.     

Norepinephrine-containing glomus cells in the rabbit carotid body. I. Autoradiographic and morphometric study after tritiated norepinephrine uptake

Summary Rabbit carotid bodies were investigated by autoradiography at both the light and electron microscope levels following tritiated norepinephrine administration eitherin vivo orin vitro. Two kinds of labelled structures were found: nerve fibres (absent in sympathectomized carotid bodies) and some type I glomus cells. Desipramine (a specific norepinephrine uptake inhibitor) prevented labelling. Most of the labelled cells differed from unlabelled ones by the presence of (i) large dense-cored vesicles characterized by a large halo between the membrane and an eccentric dense core; (ii) a nucleus showing a more electron dense chromatin and a more irregular shape; and (iii) relatively abundant glycogen particles. A few weakly-labelled cells were characterized by a pyknotic nucleus and very swollen dense-cored vesicles, and were presumed to be degenerating.Dense core diameters of dense-cored vesicles were distributed according to a unimodal distribution in labelled cells as in unlabelled ones but with an extension towards both large and very small diameters in labelled cells. The mean diameter was higher in labelled cells than in unlabelled ones (127 nm versus 113 nm,P < 0.01). The labelling intensity (as estimated by the number of silver grains per unit of cytoplasmic area) was maximum in cells having dense-cored vesicles whose mean diameter was between 130 and 170 nm, but decreased for cells with mean diameter of dense cores smaller than 130 nm, or larger than 170 nm.Thus, in the rabbit carotid body, some glomus cells differ from others by their ability to take up tritiated norepinephrine and by the presence of larger dense-cored vesicles. However, this distinction is not clearcut and there are many intermediates. The observations suggest a phenomenon of evolution deriving from a unique cell type and typified by both metabolic norepinephrine uptake ability, glycogen accumulation) and morphologic changes (increase in diameter of dense-cored vesicles). It seems, therefore, more appropriate to consider these results in terms of different functional states rather than different types of glomus cells.     

Sympathectomy provides evidence of dopamine storage in rat laryngeal nerve paraganglia

Catecholamine content in the recurrent and superior laryngeal nerves (RLN and SLN) of the rat was analysed by high-performance liquid chromatography after surgical and chemical sympathectomy. Sympathectomy induced by repeated injections of guanethidine did not lead to any change in the dopamine (DA) level, whereas the noradrenaline (NA) content decreased by 68% and 64% respectively in the RLN and SLN. Surgical excision of the superior cervical ganglion (SCG) did not alter the level of DA in the SLN, but caused a 60% decrease of DA in the RLN. Removal of SCG did not affect the NA levels either in the RLN or in the SLN, unless it was combined with extirpation of the middle cervical ganglion, which induced a decrease in NA in both nerves. The results indicate that much of the DA in the laryngeal nerves is stored outside the sympathetic nerve fibres, probably in the small organs earlier characterized as endoneurial paraganglia.     

Occurrence of calcitonin-positive C cells within the distal vagal ganglion and the recurrent laryngeal nerve of the chicken

The chicken ultimobranchial glands are richly supplied with nerve fibers originating from both the main trunk of the vagus nerve and its branch--the recurrent laryngeal nerve. C cells immunoreactive for calcitonin were invariably found in the large nerve bundles distributed throughout the ultimobranchial glands. In addition, these cells were often present within the distal vagal ganglia and the recurrent laryngeal nerves. The frequency of occurrence and the pattern of distribution of the C cells in the distal vagal ganglia and the recurrent laryngeal nerves were determined in chickens of various ages by means of an immunoperoxidase method with anticalcitonin and antineurofilament antisera. The left and right sides of the ultimobranchial region were asymmetrical. The left ultimobranchial gland was in close contact with the vagus nerve trunk, especially with the distal vagal ganglion, but it was separated from the recurrent laryngeal nerve. The right gland contacted the recurrent laryngeal nerves, its medial edge being frequently penetrated by the nerve, but the gland was separated from the distal vagal ganglion. On the left side, C cells were found in 25 out of 39 distal vagal ganglia but they were not distributed in the recurrent laryngeal nerve. On the right side, the cells were present in 28 out of 43 recurrent laryngeal nerves but absent in the distal vagal ganglia. The results indicate that the C cells secreting a hormone calcitonin can enter into nerves, but their occurrence is restricted to the nerves in close proximity to the ultimobranchial glands. Electron microscopic studies revealed that C cells in the nerves received numerous axon clusters enveloped with Schwann cell cytoplasm. Naked axons regarded as axon terminals were found in direct contact with the surface of C cells. They were mainly composed of efferent-type nerve endings showing the accumulation of numerous small clear vesicles and a few large dense-cored vesicles. In addition, C cells were partly covered with the long cytoplasmic processes of Schwann cells and were also in contact with the Schwann cell perikarya. The C cells in nerves appear to be controlled by neural stimulation.     

Transformation of synaptic vesicle phenotype in the intramedullary axonal arbors of cat spinal motoneurons following peripheral nerve injury

Permanent transection of a peripheral motor nerve induces a gradual elimination of whole axon collateral systems in the axotomized spinal motoneurons. There is also an initial concurrent decrease in the amount of recurrent inhibition exerted by these arbors in the spinal cord for up to 6 weeks after the injury, whereas the same reflex action returns to normal by the 12-week postoperative state. The aim of the present investigation was to study the fine structure of the intramedullary axonal arbors of axotomized α-motoneurons in the adult cat spinal cord following a permanent peripheral motor nerve lesion. For this purpose, single axotomized α-motoneurons were labeled intracellularly with horseradish peroxidase at 12 weeks after permanent transection of their peripheral motor nerve. The intramedullary portions of their motor axon and axon collateral arbors were first reconstructed at the light microscopic level and subsequently studied ultrastructurally. This study shows that the synaptic contacts made by the intramedullary axon collateral arbors of axotomized motoneurons have undergone a change in synaptic vesicle ultrastructure from spherical and clear vesicles to spherical and dense-cored vesicles at 12 weeks after the transection of their peripheral axons. We suggest that the present transformation in synaptic vesicle fine structure may also correspond to a change in the contents of these boutons. This may, in turn, be responsible for the strengthening and recovery of the recurrent inhibitory reflex action exerted by the axotomized spinal motoneurons following a prolonged permanent motor nerve injury. Electronic Publication     

Changes in volume densities and distribution of mitochondria in rat skeletal muscle after chronic hypoxia.

In order to test the hypothesis that subsarcolemmal aggregation of skeletal muscle mitochondria, as noted in some patients with mitochondrial myopathies, is caused by an impaired oxygen supply to mitochondria, we exposed two groups of rats to 8% O2 during 44 or 45 days. One group performed mild exercise, as did a normoxic control group. After hypoxia we investigated fibre type composition, fibre diameter and capillarity of soleus and extensor digitorum longus (e.d.l.) muscles. Mitochondrial volume densities were determined by morphometric analysis. In both e.d.l. and soleus muscle fibre type composition was unchanged and fibre diameter was reduced after hypoxia. Capillary network was unchanged, hence capillary density was increased in both muscles after hypoxia (P less than 0.05 in untrained soleus). Total mitochondrial volume density was increased in soleus muscle, which was due to an increase in the volume density of intermyofibrillar mitochondria (P less than 0.05 in the trained group), whereas the volume density of subsarcolemmal mitochondria decreased. In e.d.l. muscle the volume density of both intermyofibrillar and subsarcolemmal mitochondria decreased. We conclude that subsarcolemmal aggregation of mitochondria did not occur after chronic hypoxia. In soleus and e.d.l. muscle, different changes in the volume densities of mitochondria occurred. This may be related to the relative amounts of type I and type II fibres within these muscles.     

Noradrenaline content correlated to matrix density in small noradrenergic vesicles from rat seminal ducts

The relation between matrix density and noradrenaline content has been investigated in a fraction of small noradrenergic storage vesicles obtained from seminal ducts of castrated rats by density gradient centrifugation. This preparation contained numerous dense-cored small vesicles with an increased diameter but with a similar appearance to those in nerve terminals in the intact vas deferens.After incubation of the vesicle fraction for 20 min at 30°C in the presence of noradrenaline, Mg²⁺ and adenosine 5'-triphosphate, about 50–60% of the vesicles with a diameter of 40–70 nm contained dense cores, in some regions of the sediment even up to 80%. This correlated well with a high level of sedimentable noradrenaline, 150% of control.Incubation of vesicles without exogenous noradrenaline in the presence of Mg²⁺ and adenosine 5'-triphosphate yielded mostly electron-lucent vesicles, and biochemically only 40% of the control level of noradrenaline was retained in the particulate fraction after centrifugation. A similar depletion of electron dense-core material was observed after incubation with tyramine, Mg²⁺ and adenosine 5'-triphosphate, where only 55% of the sedimentable noradrenaline as compared to control was retained. In this respect the small dense-cored vesicles differed markedly from the large dense-cored vesicles purified from bovine splenic nerve, where the dense cores were retained in spite of a 70–80% depletion of noradrenaline after incubation in the presence of tyramine.Incubation with 5-hydroxydopamine did not significantly increase the electron density of the small dense-cored vesicles, in contrast to the marked effect of this agent when administered in vivo. Incubation with reserpine and atractyloside did not affect either noradrenaline release or vesicle morphology significantly, whereas treatment with N-ethylmaleimide gave a 60% decrease in particulate noradrenaline content but only a moderate reduction in electron density.The results indicate that both noradrenaline and, to a lesser extent, other matrix material in the presence of Mg²⁺ and adenosine 5′-triphosphate are capable of forming electron-dense cores, and that noradrenaline is more important for dense-core formation in small noradrenergic vesicles than it is in the large vesicles.     

喉返神经对大鼠甲状腺摄碘的影响及其机制探讨

（１）切断大鼠单侧喉返神经２、４、２４ｈ后同侧甲状腺摄碘量均明显增高，而在切断单侧喉返神经４ｈ后电刺激其外周端则该侧甲状腺摄碘量较单纯切断神经者减少，事先给以阿托品可阻断电刺激引起的效应。（２）切断大鼠单侧喉返神经１ｄ后，该侧甲状腺滤泡上皮细胞内高尔基复合体是松散状，分泌颗粒增多。（３）切断大鼠单侧喉返神经１０ｄ后，该侧甲状腺滤泡上皮细胞内线粒体明显增多（线粒体体积密度和膜面密度均明显增加）。（４）切断单侧喉返神经或切断后电刺激其外周端所引起的效应在去垂体大鼠仍然出现。（５）切断大鼠单侧喉返神经４ｈ和２４ｈ后，下丘脑内去甲肾上腺素、多巴胺、酪氨酸三种神经递质的含量无明显变化。以上结果表明：喉返神经抑制甲状腺摄碘功能的机制可能是Ｍ受体介导的、纯神经调节作用。     

Type I cells of carotid body from rats treated with 5-OH-Dopa and L-Dopa: an electron microscopical study

Summary The ultrastructure of the Type I cells in rat carotid bodies was studied after treatment with 5-OH-Dopa and L-Dopa. Type I cells from the L-Dopa treated rats were also analysed by morphometric methods.After 5-OH-Dopa treatment, the majority of dense-cored vesicles of the Type I cells were almost completely filled withvery electron-dense material. The vesicles were mainly distributed close to the plasma membrane.After L-Dopa treatment, the ultrastructure of the Type I cells resembled that after 5-OH-Dopa treatment, except that the increase in electron density of the vesicle content was less pronounced. The morphometric analysis revealed, as previously described for normal carotid bodies, two subclasses of Type I cells, small vesicle cells (SVC) and large vesicle cells (LVC). Compared to those of normal rats, the mean profile diameter of the vesicles in theL-Dopa treated rat carotid bodies were enlarged (for SVC from 47 to 55 nm and for LVC from 63 to 76–78 nm). Furthermore, the volume density of vesicles in both SVC and LVC was increased. The mean volume of the SVC was markedly increased after L-Dopa treatment for 60 h.These observations indicate that the Type I cells possess mechanisms for uptake of amine precursors and synthesis of monoamines. Though the vesicle may be involved in an endocrine-like function, they may also be related to the chemoreceptor function of the carotid body.     

Plasticity in the phenotypic expression of catecholamines and vasoactive intestinal peptide in adult rat superior cervical and stellate ganglia after long-term hypoxia in vivo.

Sympathetic ganglia in the adult rat contain various populations of nerve cells which demonstrate plasticity with respect to their transmitter phenotype. The plasticity of the neuronal cell bodies and of the small intensely fluorescent cells in the superior cervical and stellate ganglia in response to hypoxia in vivo (10% O2 for seven days) was assessed by studying the expression of catecholamines and vasoactive intestinal peptide. The levels of norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid and vasoactive intestinal peptide immunoreactivity were determined. In addition, the density of the immunohistochemical staining of cells for tyrosine hydroxylase and vasoactive intestinal peptide was evaluated. In the intact superior cervical ganglion, hypoxia increased the dopamine level as well as the density of small intensely fluorescent cells immunolabelled for tyrosine hydroxylase and vasoactive intestinal peptide. In the axotomized ganglion, hypoxia elicited a twofold rise in the level of the vasoactive intestinal peptide as well as enhancing the density of neuronal cell bodies immunostained for this peptide. Thus, the effect of hypoxia on the expression of vasoactive intestinal peptide expression in neurons was dependent on neural interactions. In the intact stellate ganglion, hypoxia alone induced a 1.5-fold increase in the density of neuronal cell bodies immunostained for vasoactive intestinal peptide. Thus, ganglia-specific factors appeared to play a role in determining changes in neuronal phenotype in response to hypoxia. The present study provides evidence for the involvement of dopamine and vasoactive intestinal peptide in ganglionic responses to long-term hypoxia as well as for differential responses by the two ganglionic cell populations, i.e. neuronal cell bodies and small intensely fluorescent cells. Changes in the expression of the vasoactive intestinal peptide during long-term hypoxia may be of energetic, trophic and/or synaptic significance. Hypoxia may be considered to be a vasoactive intestinal peptide-inducing factor in sympathetic ganglia.     

Biogenic amines in carotid body of adult and infant rats--a gas chromatographic-mass spectrometric assay.

A gas chromatographic-mass spectrometric method was used for the determination of biogenic amines in carotid body of adult and 10 days old rats. The method is ideally suited for this measurement since only small amounts of tissue were available (dry weight carotid body: adult 8.3 mug; infant 5.6 mug). In adult carotid body large amounts of dopamine (1 950 pmol/mg protein) and norepinephrine (1 140 pmol/mg protein) were found together with a comparatively small concentration of serotonin (505 pmol/mg protein). The carotid bodies of infant rats contained 1 065 pmol dopamine/mg protein and 410 pmol norepinephrine/mg protein. Epinephrine could not be detected. Surgical sympathetic denervation and chemical sympathectomy (6-hydroxydopamine) of adult carotid bodies did not significantly change the catecholamine content as compared to the controls. Reserpine depleted the catecholamines dosedependently. Administration of L-Dopa and pargyline (a monoamineoxidaseinhibitor) drastically increased the concentration of catecholamines. Treatment with a dopamine-beta-hydroxlase-inhibitor resulted in a decreased amount of norepinephrine without a simultaneous increase of dopamine. This may indicate that certain storage sites in this tissue may store dopamine while in other sites dopamine is a precursor of norepinephrine. Probably most of the dopamine and norepinephrine are stored in different cells.