Untersuchungen �ber den Feinbau von Spinalganglien

Differential labeling by horseradish peroxidase of small and large spinal neurons of rats

Solid horseradish peroxidase (HRP) was applied to the crushed peroneal nerves of rats and its retrograde transport to spinal ganglion cells and spinal motoneurons was examined after varying survival times. Following short (22-39 h) survival times predominantly small sensory and motoneuronal cell bodies contained HRP. Following long intervals (72-96 h), the percentage of labeled large cells increased in both groups of neurons. The differences were more pronounced in sensory than in motoneurons.

Substance P in the vagal sensory ganglia: localization in cell bodies and pericellular arborizations

The distribution of Substance P-like immunoreactivity in the jugular and nodose ganglia of rabbits and pigeons has been studied using immunocytochemical staining techniques. Substance P-like immunoreactivity is localized to neuronal cell bodies and processes in the jugular and nodose ganglia, and to pericellular fiber plexi in the nodose ganglia of both species. The numbers and sizes of cells which exhibited Substance P-like immunoreactivity in each ganglion were determined using quantitative morphometric techniques. The distribution of Substance P-like immunoreactivity in the rabbit and pigeon vagal sensory ganglia is characterized by several general features. In most of the ganglia, immunoreactive neurons factor into discrete types which can be distinguished from one another, and from non-immunoreactive neurons, by size. In addition, immunoreactive nodose and jugular ganglion cells, respectively, are distinguishable on the basis of size. Finally, a considerably high percentage of immunoreactive neurons is found in the jugular ganglion than in the nodose ganglion. Substance P-like immunoreactivity was also seen in pericellular fiber plexi which encircle individual neurons in the nodose ganglion of rabbits and pigeons. These plexi are composed of varicose fibers which appear to terminate as boutons on the surface of the cells which they encircle. The distribution of Substance P-like immunoreactivity within the vagal sensory ganglia is discussed with respect to the possible peripheral targets and functions of Substance P-containing vagal afferents. Our findings suggest that Substance P-containing vagal sensory neurons are involved in a variety of visceral and somatic afferent functions.

Ageing of the spinal ganglion neurons in the rat: a radioautographic study following injection of [3H]lysine

After administration of [3H]lysine to 3- and 24-month-old rats, radioautography demonstrates a significantly less important uptake in the A-type spinal ganglion neurons and in the old animals. This is in agreement with the existence of at least two functional categories of neurons in the spinal ganglion and suggests that protein synthesis is diminished in the old animals. The very fact that incorporation varies between animals of the same age sustains the hypothesis according to which amplitude of ageing is essentially an individual physiological-dependent process.

Somatotopic and functional organization of the avian trigeminal ganglion: an HRP analysis in the hatchling chick

While the somatotopic organization of many central systems is well characterized, that of peripheral sensory neurons has not been adequately defined. This is especially true for the trigeminal ganglion. By applying HRP subcutaneously at each of 14 sites and also intramuscularly, it is possible to determine whether the location of sensory neurons within the ganglion reflects their peripheral projections. There is no discernible somatotopic organization of neurons in the ophthalmic lobe. However, the location of maxillary neurons in the maxillo-mandibular lobe is organized with the most posterior cells projecting to sites closest to the ganglion and with neurons located more anteriorly projecting to progressively more distant sites. There is a less well defined organization in the superior-inferior axis of the ganglion, and none along its proximal (root) to distal axis. Mandibular exteroceptive neurons are found primarily in the anterior region of the maxillo-mandibular lobe, while mandibular proprioceptive cells are located in the proximo-central part of this lobe. In most cases there is a considerable scattering of horseradish peroxidase (HRP)-filled neurons. Projections to contralateral ganglia, the trigeminal motor nucleus, and the trigeminal mesencephalic nucleus were also examined. Cytologically, the hatchling trigeminal consists of two interspersed types of neurons: large, lightly staining and smaller, darkly staining cells. Previous experiments have proved that these two cell types do not correspond to each of the embryonic precursors of trigeminal neurons, the neural crest and placodal cells. In this study HRP was found localized in both classes of neurons following injection at all sites, including jaw-closing muscles. This indicates that the dual cytology is not correlated with either distribution of peripheral fibers or exteroceptive vs. proprioceptive functions. The possibilities that the two types of neurons may have different central projections and/or may be related to visceral vs. somatic afferent functions are discussed.

The postnatal development of large light and small dark neurons in mouse dorsal root ganglia: a statistical analysis of cell numbers and size

A method is described for the analysis of cell types in mouse dorsal root ganglia using the distribution of cell cross-sectional areas measured at the level of the nucleolus in 1.5 micron Epon sections. Using a computer program it was possible to demonstrate the existence of two normally distributed sub-populations of neurons in all the 3rd lumbar segment ganglia (17 in number) measured at various ages from birth to 70 days. The two populations appeared to correspond with large light cells and small dark cells. The large light cell bodies increased in size until about 20 days postnatal, subsequently their size decreased whereas the mean size of the small dark cells reached a plateau by about day 10. The relationship of both nuclear volume and surface area to the surface area of the perikaryon differed between light and dark cells. The number of neurons in L3 remained virtually constant at about 6000 throughout the period examined. Since the proportion of neurons in each population was not shown to change with age there was no evidence that cells could change from one type into the other.

The generation of neurons involved in an early reflex pathway of embryonic mouse spinal cord

The generation of lateral motor neurons (LMNs), interneurons and dorsal root ganglion (DRG) neurons of the cervical mouse spinal cord has been investigated by [3H]thymidine autoradiographic techniques. This investigation has two main objectives: (a) to determine on which embryonic days these three neuronal populations are born, and (b) to investigate the possibility that the neurons comprising early reflex circuits might be formed by a retrograde temporal sequencing of generation. LMNs are the first neurons generated in the cervical spinal cord. They arise between E8.8 and E11.5, and approximately 90% of these cells are born within a 36-hour period between E9 and E10.5. The earliest time of origin for interneurons is on E9.5, and those cells which are generated between E9.5 and E10.5 cluster in two distinct regions of the adult spinal cord. One of these regions is the lateral portions of laminae IV through VI; this appears to be the location of many ipsilateral association neurons. DRG neurons begin to arise on E9.5 and their generation is completed by E14. There is a trend within the DRG population for large neurons to be born before small neurons. Those cells with diameters of 40 micron or greater reach their generation peak on E10.5, while those smaller than 40 micron arise in the greatest numbers on E12. The findings of other investigations have provided evidence for a retrograde sequence of synaptic closure in the formation of the early disynaptic forelimb reflex pathway. The temporal difference in synapse formation in the terminal fields of DRG and association neurons is discussed in terms of our observation that both of these populations appear to have similar generation times. We suggest that factors responsible for the delayed synaptic closure of DRG afferents include the greater distances and the degree of collateralization which these afferents must undergo in order to establish their terminal fields. Finally, we discuss the possibility that the temporal sequence of neuronal generation and factors involved with the growth of neurites combine to produce a retrograde sequence of synaptic closure in the early disynaptic forelimb reflex pathway of mouse spinal cord.

Appearance of histochemically detectable ionic calcium in degenerating primary sensory neurons

The effect of neonatal capsaicin treatment on the fine structure and localization of ionic calcium in sensory ganglion cells has been investigated in rats. Neonatal capsaicin treatment resulted in the degeneration of certain type B sensory neurons. At the same time ionic calcium was demonstrated histochemically in the perikarya of numerous small-sized ganglion cells. The appearance of histochemically detectable ionic calcium in these cells in relation to the pharmacologically evoked degeneration of certain primary sensory neurons is discussed.

Localization of substance P-like immunoreactivity in nerves in the tooth pulp

The occurrence of substance P (SP)-like immunoreactivity was studied in dental pulps of the cat. In untreated animals SP-positive fibres were found in all areas of the pulp. Most fibres were seen in central parts of the pulp but they were also observed in relation to the odontoblasts. Single, possibly unmyelinated, or fine caliber fibres or small bundles of them were seen running close to large non-fluorescent myelinated nerves, to blood vessels or without any obvious association with either of these structures. Fourteen days after transection of the inferior alveolar nerve no SP-positive fibres were observed in pulps on the denervated side. Transection of the cervical sympathetic ganglion did not change the occurrence of SP-positive fibres. The results indicate the existence of at least two types of afferent fibres in the dental pulp of the cat. Since the tooth pulp has been demonstrated to give rise only to pain sensation when stimulated, the results give morphological support for a role of SP neurones in pain transmission.

On the occurrence of substance P-containing fibers in sympathetic ganglia: immunohistochemical evidence

Several sympathetic ganglia of the guinea pig, cat and rat were studied with indirect immunofluorescence technique using antibodies to substance P (SP) and dopamine-beta-hydroxylase (DBH), the latter of which represents a marker for noradrenaline containing neurons. In all ganglia studied SP-like immunoreactivity could be observed in certain nerve fibers (SP-positive fibers). Their number, localization fluorescence intensity and 'fluorescence morphology' varied considerably between the different ganglia as well as between species. In the inferior mesenteric ganglion and the coeliac-superior mesenteric ganglion complex of all species, and in particular of the guinea pig, a dense plexus of varicose SP-positive fibers was observed around the mostly DBH-positive, principal ganglion cells. In contrast no such fibers were seen in relation to the DBH-positive SIF cells of the ganglia. No SP-positive ganglion cells were observed in any of the ganglia studied. Previous biochemical and immunohistochemical studies have indicated that peripheral SP-positive fibers may represent the branches of primary sensory neurons. The rich supply of varicose, SP-positive nerve terminals, often surrounding the noradrenergic ganglion cells in a basket-like manner, may indicate that these fibers may play a functional role within the ganglia. Instead of merely passing through the ganglion they may be involved in special types of reflex arches.

An ultrastructural study of cat petrosal ganglia: a search for autonomic ganglion cells

It is not known whether cranial and spinal ganglia contain autonomic (motor) neurons in addition to sensory cells. Early light microscopic studies indicate the possibility of synaptic input to some nerve cells via perisomatic axon terminals and dendrites. It has also been suggested that visceromotor relay-type cells in the petrosal ganglion might be involved in the efferent control of the carotid body. The present ultrastructural analysis of 902 neurons in 17 levels from two cat petrosal ganglia provides no evidence for synapses on the cell somata or on their axonal extensions. Processes resembling dendrites were lacking although small surface projections typical of sensory cells were common. The petrosal ganglion thus appears to consist entirely of afferent unipolar neurons.

Fenestrated blood capillaries in rat cranio-spinal sensory ganglia

Several fenestrated capillaries were seen in the endoneurium of trigeminal and dorsal root ganglia from two young adult albino rats treated with tetraethylthiuram disulfide. The finding is regarded as normal, although the possibility exists that intoxication with tetraethylthiuram disulfide may have enhanced the intensity and/or rate of this cytologic specialization of some isolated endothelial cells.

A histochemical investigation on mucopolysaccharides in the dog sympathetic ganglia

A histochemical study in the dog Superior Cervical ganglion and in the Cervicothoracic or Stellate ganglion is reported. The mucopolysaccharide composition of these ganglia are studied by means of five histochemical techniques. The different histochemical composition between the neurons of these ganglia is investigated. In the sections stained with the PAS technique some neurons appeared more intensely stained than the others. With Thionin or Toluidine blue some neurones appeared more metachromatic than others. A peculiar distribution of the Nissl bodies, related with metachromasia, is reported. In sections stained with the Colloidal Iron method yellow neurons like those presented in the dorsal root ganglia were not found in the sympathetic ganglia. This fact suggests that the yellow neurons might be a different type of neuron. The possibility that the staining variations associated to the distribution of the Nissl bodies perhaps correspond to different functional states of the same type of neurons is also suggested.

Specificity of retrograde transport of nerve growth factor (NGF) in sensory neurons: a biochemical and morphological study

In previous studies it has been shown that nerve growth factor (NGF) is taken up with a high selectivity by adrenergic nerve terminals and is transported retrogradely to the perikaryon11,22. It was the aim of the present experiments to investigate whether the sensory neurons exhibit the same high degree of selectivity for retrograde transport throughout the whole life cycle, although it is known that their dramatic response to NGF is confined to a short period of ontogenetic development. Unilateral injection of [125I]NGF into the forepaw of adult rats was followed by a preferential accumulation of radioactivity in the sensory ganglia (C6-C7) of the injected side. However, this preferential accumulation was not detectable earlier than 6 h after injection and reached a maximum (ratio between injected and non-injected side, 5:1) after 11-16 h. Transection of the plexus brachialis abolished and local administration of colchicine prior to that of [125I]NGF greatly reduced the preferential accumulation of radioactivity in the ganglia of the injected side. The rate of retrograde transport of NGF in sensory neurons was calculated to be 13 mm/h which is about 5 times faster than that in adrenergic neurons. The selectivity of this retrograde transport was demonstrated by the fact that injection of 125I-labeled bovine serum albumin and cytochrome c did not result in a preferential accumulation of radioactivity in the sensory ganglia of the injected side. Light microscopic autoradiography revealed heavily labeled cells in the sensory ganglia (C6-C7) of the injected side after administration of [125I]NGF into the forepaw. Only cells belonging to the large cell type were labeled. Prolonged (7 mug/g/day over 5 days) injection of NGF into the forepaw of 10-day-old rats did not result in a hypertropic response of the sensory neurons as far as can be judged from morphometric studies at the light microscopic level.

Quantitative relationships between nerve and satellite cells in spinal ganglia: an electron microscopical study. II. Reptiles

In the spinal ganglia of two species of reptiles (gecko and lizard) the volume of the perikaryal satellite cell sheath was found directly proportional both to the volume and surface area of the related neuronal body. This result agrees with that obtained in a previous research on two species of mammals (cat and rabbit). A quantitative balance between neuronal bodies and their associated glial tissue therefore exists also in the spinal ganglia of zoological species phylogenetically quite distant from mammals. The quantitative relationship between glial and nerve tissue was found to be lower in the gecko and lizard than in the cat and rabbit. This difference could have a phylogenetic significance, and/or it could be explained by the lower metabolic rate in the nervous system of the poikilotherms in respect to mammals.

Functional and fine structural characteristics of the sensory neuron blocking effect of capsaicin

In the eye of rats the long-lasting specific desensitization induced by local or systemic capsaicin treatment is characterized by three phases: 1. complete insensitivity, 2. decreased sensitivity and a tendency to rapid adaptation, 3. normal initial sensitivity with a tendency to rapid adaptation to chemical pain stimuli. A low density of nicrovesicles and swollen mitochondria were found after local capsaicin treatment in certain nerve endings of the cornea of rats, but no signs of axonal degeneration or alteration in fine structure of non-neural elements were seen. Systemic capsaicin desensitization induced selective mitochondrial swelling in B type of neurons of the trigeminal ganglion which was demonstrable even 60 days after the pretreatment. Actinomycin-D, 8-azaguanine, 6-azauracil, aminopterin, mannomustin or cycloheximide in high doses did not alter the desensitizing effect of systemic capsaicin treatment. However, pretreatment of rats with colchicine or vinblastine prolonged the desensitizing effect of local capsaicin application, probably by inhibiting the axonal flow. It is concluded that capsaicin is a specific sensory neuron blocking agent having a practically irreversible effect in rats and guinea-pigs.