The ultrastructure of the intestinal nerve of Remak in the domestic fowl

Summary An ultrastructural study was made of the neurons, satellite cells and vesiculated axons of the intestinal nerve of the domestic fowl. Broad membrane-to-membrane contacts between adjacent nerve cell bodies were sometimes observed. The cell bodies and processes were not always separated from the extracellular space by a capsule of satellite cells. Following fixation using potassium permanganate, catecholamine (CA)-containing neurons in the intestinal nerve, unlike those in the lumbar parasympathetic ganglia, did not possess any small granular vesicles (SGV). Following exposure to noradrenaline, SGV could be demonstrated in the cell bodies of the juxta-ileal ganglia but not the juxta-rectal ganglia of the intestinal nerve. Non-CA axons were examined in tissue from birds that had been pretreated with 6-hydroxydopamine. Approximately one half of the non-CA axons formed axo-somatic contacts. Most of the non-CA axons contained varying proportions of small clear vesicles, large clear vesicles and large granular vescles. Statistical analysis showed that the non-CA axons could not be subdivided according to their vesicle content. CA-axons contained many SGV and were found in close apposition to neuronal somata and processes, and in the neuropil.     

Distribution of dopamine and octopamine in the central nervous system and ovary during the ovarian maturation cycle of the giant freshwater prawn, Macrobrachium rosenbergii

Dopamine (DA), octopamine (OA) and serotonin (5-HT) are the key neurotransmitters that control gonadal development in decapod crustaceans. 5-HT stimulates, while DA and OA delay gonadal development in Macrobrachium rosenbergii. In the present study, we have further investigated the distribution patterns of DA and OA in the central nervous system (CNS) and ovary during various stages of the ovarian maturation cycle of this giant freshwater prawn. DA- and OA-immunoreactive neurons and fibers were distributed extensively in several regions of the brain, subesophageal ganglion (SEG), thoracic ganglia and abdominal ganglia. In the brain, the two neurotransmitters were present in neurons of clusters 6, 7, 11, 17, and nearby neuropil regions. In the SEG, thoracic ganglia and abdominal ganglia, immunoreactive neurons and fibers were found along the midline and in several neuronal clusters around each neuropil region. Staining for DA and OA was more intense in the thoracic ganglia than in other parts of the CNS. In the ovary, DA- and OA-immunoreactivities were present at high intensity in early oocytes. The presence of DA- and OA-immunoreactivities in neural ganglia as well as ovary suggests that DA and OA may also be involved in the reproductive process, particularly ovarian development and differentiation of oocytes in this species.     

Localization of ovulation hormone-like neuropeptide in the central nervous system of the snail Lymnaea stagnalis by means of immunocytochemistry and in situ hybridization

Summary The caudo-dorsal cells (CDC) in the cerebral ganglia of the pond snail Lymnaea stagnalis synthesize the 36-amino acid ovulation hormone (CDCH). We have used immuno-cytochemistry and in situ hybridization to reveal the localization of neurons and axons containing CDCH-like material.A monoclonal antibody to a fragment of CDCH and a cDNA probe encoding CDCH reacted with the CDC-system, with specific cell groups in the cerebral and pleural ganglia, and with individually occurring neurons throughout the central nervous system. The cells in the pleural ganglia, which were found in about 50% of the preparations studied, are considered as ectopic CDC. They are morphologically similar to CDC in their somal dimensions and axonal organization. By means of immuno-electron microscopy it was shown that these neurons contain secretory vesicles that are similar to those of the CDC. The neurons of the bilateral groups occurring in the cerebral ganglia in addition to the CDC are smaller and more intensely stained than the CDC. Axons of these small neurons probably have varicosities located on the CDC axons in the neuropil of the cerebral ganglion, indicating synaptic contacts. Two major axon tracts could be followed from (or toward) the neuropil of the cerebral ganglion. One tract runs from the cerebral gangion via the pleural and parietal ganglia to the visceral ganglion, giving off branches to most nerves emanating from these ganglia. The other tract could be traced through the cerebro-pedal connective to the pedal ganglia. Only in the right pedal ganglion was extensive axonal branching observed. The nerves emanating from this ganglion contained many more immunoreactive axons than those from the left pedal ganglion. A polyclonal antibody raised against the synthetic fragment of CDCH stained, in addition to the neurons and axons revealed with the monoclonal antibody and the cDNA probe, three other major groups of neurons. Two are located in the cerebral ganglion, the other in the left pedal ganglion.The present findings suggest the presence of a system of neurons that contain CDCH or CDCH-like peptides. The role this system may play in the control of egg-laying and egg-laying behaviour is discussed.     

Electron microscopy of the mucosal plexus of the rat colon.

The ultrastructure of neurons, glial cells and axons of the mucosal plexus of the rat colon descendens was studied. Serial semithin sections and a re-embedding technique were used in order to localize the ganglia. The ganglia are free of blood vessels and connective tissue. The ratio of neurons to glial cells is approximately 1. Ganglia and nerve strands are enclosed by a basement membrane, without a well-defined perineural connective tissue. The neurons show a structure similar to other enteric plexus. Synaptic contacts were observed frequently in the neuropil, where nerve endings and varicosities show a diverse outfit in vesicles. The glial cells, which contain immunocytochemically detectable glial fibrillary protein, possess the same ultrastructural attributes in the intra- and extraganglionic localizations. In the nerves, axonic profiles and varicosities appear in close relation with glial cells or their processes. The distance between the nerves and their target cells, i.e. the enterocytes, is 0.5 microns or more with interposed basement membranes and fibroblasts.     

Neurons of the central nervous system innervating the lips and oral area of the pond snail

By means of retrograde transport methods, CoCl2 and horseradish peroxidase, localization and morphological peculiarities of the CNS neurons, that innervate lips and oral area, have been studied in the pond snail (Gastropoda). The neurons, sending their processes into the anterior and middle labial nerves, are found nearly in all ganglia of the parapharyngeal nervous ring on the distal and ventral surface. In the cerebral ganglia they situate as several symmetrical groups. Among the neurons revealed, there are cells with rather local distribution of the terminal branches of the processes in the CNS neuropil and neurons with vast branching areas in the neuropil not only of its own ganglion, but also of the neighbouring ones. The problem concerning the zones of possible intersensory interaction in the cerebral ganglia is discussed and presence in them, together with complex reflectory arches, of bisegmental reflectory arches is considered.     

Mapping of serotonin-immunoreactive neurons in the larval nervous system of the flies Calliphora erythrocephala and Sarcophaga bullata

Summary Serotonin-immunoreactive (5-HTi) neurons were mapped in the larval central nervous system (CNS) of the dipterous flies Calliphora erythrocephala and Sarcophaga bullata. Immunocytochemistry was performed on cryostat sections, paraffin sections, and on the entire CNS (whole mounts).The CNS of larvae displays 96–98 5-HTi cell bodies. The location of the cell bodies within the segmental cerebral and ventral ganglia is consistent among individuals. The pattern of immunoreactive fibers in tracts and within neuropil regions of the CNS was resolved in detail. Some 5-HTi neurons in the CNS possess axons that run through peripheral nerves (antenno-labro-frontal nerves).The suboesophagealand thoracico-abdominal ganglia of the adult blowflies were studied for a comparison with the larval ventral ganglia. In the thoracico-abdominal ganglia of adults the same number of 5-HTi cell bodies was found as in the larvae except in the metathoracic ganglion, which in the adult contains two cell bodies less than in the larva. The immunoreactive processes within the neuropil of the adult thoracico-abdominal ganglia form more elaborate patterns than those of the larvae, but the basic organization of major fiber tracts was similar in larval and adult ganglia. Some aspects of postembryonic development are discussed in relation to the transformation of the distribution of 5-HTi neurons and their processes into the adult pattern.     

Expression of GABA transaminase immunoreactivity in interneurons of the rat neostriatum

Immunoreactivity for γ-aminobutyric acid transaminase (GABA-T), a degradation enzyme for GABA, was localized by immunocytochemistry in the rat neostriatum and the globus pallidus using a monoclonal antibody. Immunoreactivity for GABA-T was found primarily in interneurons and in the neuropilar elements in the neostriatum. Many of GABA-T-immunoreactive neurons were found to display parvalbumin immunoreactivity. This indicates many of the GABA-T-immunoreactive neurons are striatal GABAergic interneurons. Occasionally, GABA-T-immunoreactive glial cells were found. In the globus pallidus, many pallidal neurons also displayed GABA-T immunoreactivity and many of the immunoreactive neurons were seen to express parvalbumin immunoreactivity. Immunoreactivity for GABA-T was also detected in the neuropil of the globus pallidus. The present results indicate the GABAergic interneurons in the neostriatum and a subpopulation of pallidal neurons play an important role in metabolic degradation of GABA in the basal ganglia.     

Transplantation of neurons reveals processing areas and rules for synaptic connectivity in the cricket nervous system

In order to assess the nature of spatial cues in determining the characteristic projection sites of sensory neurons in the CNS, we have transplanted sensory neurons of the cricket Acheta domesticus to ectopic locations. Thoracic campaniform sensilla (CS) function as proprioceptors and project to an intermediate layer of neuropil in thoracic ganglia while cercal CS transduce tactile information and project into a ventral layer in the terminal abdominal ganglion (TAG). When transplanted to ectopic locations, these afferents retain their modality-specific projection in the host ganglion and terminate in the layer of neuropil homologous to that of their ganglion of origin. Thus, thoracic CS neurons project to intermediate neuropil when transplanted to the abdomen and cercal CS neurons project to a ventral layer of neuropil when transplanted to the thorax. We conclude that CS can be separated into two classes based on their characteristic axonal projections within each segmental ganglion. We also found that the sensory neurons innervating tactile hairs project to ventral neuropil in any ganglion they encounter after transplantation. Ectopic sensory neurons can form functional synaptic connections with identified interneurons located within the host ganglia. The new contacts formed by these ectopic sensory neurons can be with normal targets, which arborize within the same layer of neuropil in each segmental ganglion, or with novel targets, which lack dendrites in the normal ganglion and are thus normally unavailable for synaptogenesis. These observations suggest that a limited set of molecular markers are utilized for cell–cell recognition in each segmentally homologous ganglion. Regenerating sensory neurons can recognize novel postsynaptic neurons if they have dendrites in the appropriate layer of neuropil. We suggest that spatial constraints produced by the segmentation and the modality-specific layering of the nervous system have a pivotal role in determining synaptic specificity. © 1993 John Wiley & Sons, Inc.     

Localization of glutamate-like immunoreactive neurons in the central and peripheral nervous system of the adult and developing pond snail, Lymnaea stagnalis

We investigated the distribution and projection patterns of central and peripheral glutamate-like immunoreactive (GLU-LIR) neurons in the adult and developing nervous system of Lymnaea. Altogether, 50-60 GLU-LIR neurons are present in the adult central nervous system. GLU-LIR labeling is shown in the interganglionic bundle system and at the varicosities in neuropil of the central ganglia. In the periphery, the foot, lip, and tentacle contain numerous GLU-LIR bipolar sensory neurons. In the juvenile Lymnaea, GLU-LIR elements at the periphery display a pattern of distribution similar to that seen in adults, whereas labeled neurons increase in number in the different ganglia of the central nervous system from juvenile stage P1 up to adulthood. During embryogenesis, GLU-LIR innervation can be detected first at the 50% stage of embryonic development (the E50% stage) in the neuropil of the cerebral and pedal ganglia, followed by the emergence of labeled pedal nerve roots at the E75% stage. Before hatching, at the E90% stage, a few GLU-LIR sensory cells can be found in the caudal foot region. Our findings indicate a wide range of occurrence and a broad role for glutamate in the gastropod nervous system; hence they provide a basis for future studies on glutamatergic events in networks underlying different behaviors.     

The ultrastructure of the cardiac ganglion of the desert scorpion,Paruroctonus mesaensis (Scorpionida: Vaejovidae)

Light and electron microscopy of the pacemaker ganglion of the scorpion heart indicate that it is about 15 mm long and 50 μm in diameter and extends along the dorsal midline of the heart. The largest cell bodies (30–45 μm in diameter) occur in clusters along the length of the ganglion. The ganglion appears to be innervated with fibers from the subesophageal and first three abdominal ganglia. The cardiac ganglion is surrounded by a neurilemma and a membranous sheath. The latter is apparently derived from connective tissue cells seen outside the ganglion. Nerve fibers other than those in the neuropil areas are usually surrounded by membrane and cytoplasm of glial cells. Often there are several layers of glial membrane, forming a loose myelin. The cardiac nerves to the heart muscle are also surrounded by a neurilemma, and the axons are surrounded by glia. The motor nerves contain lucent vesicles 60–100 nm and opaque granules 120–180 nm in diameter. In the cardiac ganglion, some nerve cell bodies have complex invaginations of glial processes forming a peripheral trophospongium. In the neuropil areas, nerve cell processes are often in close apposition. The septilaminar configuration typical of gap junctions is common, with gap distances of 1–4 nm. In tissues stained with lanthanum phosphate during fixation, we found gaps with unstained connections (1–2 nm diameter) between nerve-nerve and glial-nerve cell processes. Annular or double-membrane vesicles in various stages of formation were also seen in some nerve fibers in ganglia stained with lanthanum phosphate. Nerve endings with electron-lucent vesicles 40–60 nm in diameter are abundant in the cardiac ganglion, suggesting that these contain the excitatory transmitter of intrinsic neurons of the ganglion. Less abundant are fibers with membrane-limited opaque granules, circular or oblong in shape and as much as 330 nm in their longest dimension. Also seen were some nerve endings with both vesicles and granules.     

Neurocalcin-like immunoreactivity in the rat esophageal nervous system

Neurocalcin is a newly identified neuronal calcium-binding protein. We tried here to investigate the immunohistochemical distribution of neurocalcin in the rat esophagus. Nerve cell bodies having neurocalcin immunoreactivity were found throughout the myenteric plexus. In the myenteric ganglia, two types of nerve terminals showed neurocalcin immunoreactivity. One was varicose terminals containing numerous small clear vesicles and forming a synapse with nerve cells. The other terminals were characterized by laminar or pleomorphic structure and many mitochondria. These laminar terminals were supposed to be sensory receptors of the esophageal wall. In the motor endplates of the striated muscles, nerve terminals containing many small clear vesicles and mitochondria also had neurocalcin immunoreactivity. After left vagus nerve cutting under the nodose ganglia, the number of immunopositive thick nerve fibers, laminar endings and nerve terminals on the striated muscles decreased markedly. Retrograde tracing experiments using Fast Blue showed extrinsic innervation of esophagus from ambiguus nucleus, dorsal motor nucleus of vagus, superior cervical ganglia, celiac ganglia, nodose ganglia and dorsal root ganglia. In the celiac ganglia, nodose ganglia and dorsal root ganglia, retrogradely labeled nerve cells were neurocalcin-immunoreactive. Neurons in the celiac ganglia may project varicose terminals, while nodose and dorsal root neurons project laminar terminals. Although cell bodies of motoneurons in the ambiguus nucleus lacked neurocalcin immunoreactivity, these neurons may contain neurocalcin only in the nerve terminals in the motor endplates. Neurocalcin immunoreactivity is distributed in many extrinsic and intrinsic neurons in the esophagus and this protein may play important roles in regulating calcium signaling in the neurons.     

Localization of connexins in neurons and glia cells of the Helix aspersa suboesophageal brain ganglia by immunocytochemistry

The aim of the present study was to examine the distribution of cells expressing connexin 26 (Cx26) in the suboesophageal visceral, left and right parietal and left and right pleural ganglia of the snail Helix aspersa by immunocytochemistry. Altogether we have found approximately 452 immunoreactive neurons which represent the 4.7% of the total neurons counted. The stained large neurons (measured diameter 55-140 microm) occurred mostly on the peripheral surface of the ganglia while the small immunostained cells (5-25 microm diameter) were observed in groups near the neuropil. The number of large neurons giving positive Cx26-like immunostaining was small in comparison with that for medium (30-50 microm diameter) and small sized cells. The expression of Cx26 was also observed in the processes of glia cells localized among neurons somata and in the neuropil showing that the antiserum recognized epitopes in both protoplasmic and fibrous glia cells of Helix aspersa. The neuropils of all ganglia showed fibers densely immunostained. While we have observed a good specificity for Cx26-antiserum in neurons, a lack of reaction for Cx43 antiserum was observed in neurons and glia cells. The reaction for enolase antiserum in neurons was light and non-specific and a lack of reaction in glia cells and processes for GFAP antiserum was observed. Although the percentage of positive neurons for Cx26 antiserum was low is suggested that in normal physiological conditions or under stimulation the expression of connexin could be increased. The observed results can be considered of interest in the interpretation of Helix aspersa elemental two neuron networks synchronizing activity, observed under applied extremely low frequency magnetic fields.     

Distribution and anatomy of GABA-like immunoreactive neurons in the central and peripheral nervous system of the snail Helix pomatia

Gamma-aminobutyric acid (GABA)-like immunoreactive neurons were studied in the central and peripheral nervous system of Helix pomatia by applying immunocytochemistry on whole-mount preparations and serial paraffin sections. GABA-immunoreactive cell bodies were found in the buccal, cerebral and pedal ganglia, but only GABA-immunoreactive fibers were found in the viscero-parietal-pleural ganglion complex. The majority of GABA-immunoreactive cell bodies were located in the pedal ganglia but a few could be found in the buccal ganglia. Varicose GABA-ir fibers could be seen in the neuropil areas and in distinct areas of the cell body layer of the ganglia. The majority of GABA-ir axonal processes run into the connectives and commissures of the ganglia, indicating an important central integrative role of GABA-immunoreactive neurons. GABA may also have a peripheral role, since GABA-immunoreactive fibers could be demonstrated in peripheral nerves and the lips. Glutamate injection did not change the number or distribution of GABA-immunoreactive neurons, but induced GABA immunoreactivity in elements of the connective tissue ensheathing the muscle cells and fibers of the buccal musculature. This shows that GABA may be present in different non-neural tissues as a product of general metabolic pathways.     

Tyrosine hydroxylase in the cerebral ganglia of the American cockroach (Periplaneta americana L.): an immunohistochemical study

We have investigated the distribution of tyrosine-hydroxylase-like immunoreactivity in the cerebral ganglia of the American cockroach, Periplaneta americana. Groups of tyrosine-hydroxylase-immunoreactive cell bodies occur in various parts of the three regions of the cerebral ganglia. In the protocerebrum, single large neurons or small groups of neurons are located in the lateral neuropil, adjacent to the calyces, and in the dorsal portion of the pars intercerebralis. Small scattered cell bodies are found in the outer layers of the optic lobe, and clusters of larger cell bodies can be found in the deutocerebrum, medial and lateral to the antennal glomeruli. Thick bundles of tyrosine-hydroxylase-positive nerve fibers traverse the neuropil in the proto- and deutocerebrum and innervate the glomerular and the nonglomerular neuropil with fine varicose terminals. Dense terminal patterns are present in the medulla and lobula of the optic lobe, the pars intercerebralis, the medial tritocerebrum, and the area surrounding the antennal glomeruli, the central body and the mushroom bodies. The pattern of tyrosine-hydroxylase-like immunoreactivity is similar to that previously described for catecholaminergic neurons, but it is distinctly different from the distribution of histaminergic and serotonergic neurons.     

Anatomy and physiology of neurons composing the commissural ring nerve of the cricket, Acheta domesticus

The commissural ring nerve (RN) of the cricket Acheta domesticus links together the two cercal motor nerves of the terminal abdominal ganglion. It contains the axons of almost 100 neurons including two bilateral clusters of eight to 13 ventrolateral neurons and approximately 75 neurons with midline somata within the terminal abdominal ganglion. The ventrolateral neurons have an ipsilateral dendritic arborization within the dorsal neuropil of the ganglion and their axons use the RN as a commissure in order to enter the contralateral nerves of the tenth ganglionic neuromere. In contrast, most midline neurons have bifurcating axons projecting bilaterally into the neuropil of the ganglion as well as into the RN where they often branch extensively before entering the contralateral tenth nerves. Most RN neurons have small, non-spiking somata with spike initiation zones distant from the soma. Many midline neurons also produce double-peaked spikes in their somata, indicative of multiple spike initiation zones. Spontaneous neuronal activity recorded extracellularly from the RN reveals several units, some with variable firing patterns, but none responding to sensory stimuli. The RN is primarily composed of small (50 nm diameter) axon profiles with a few large (0.5-1 microm diameter) profiles. Occasionally, profiles of nerve terminals containing primarily small clear vesicles and a few large dense vesicles are observed. These vesicles can sometimes be clustered about an active zone. We conclude that the primary function of the RN is to serve as a peripheral nerve commissure and that its role as a neurohemal organ is negligible. J. Exp. Zool. 286:350-366, 2000.Copyright 2000 Wiley-Liss, Inc.     

Biogenic monoamines in Hirudo medicinalis

Summary The distribution of certain catecholamines and indoleamines in the ventral nerve cord and the body segments of the medical leech, Hirudo medicinalis, was studied with the fluorescence microscope technique of Falck and Hillarp, with microspectrofluorometry, and with chemical determinations of the amines. The six cells of the segmental ganglia previously shown to be chromaffin were found to contain an amine, most probably 5-hydroxytryptamine. In the two giant cells, the amine was found on the surface of coarse intracellular granules, lying mainly at the cell membrane, and at the nucleus. The two giant cells send their axons to the body muscles, which thus seem to have a 5-hydroxytryptaminergic innervation. The four smaller amine-containing cells of the segmental ganglia send their axons to the neuropil of the ganglion.The only cell type found to contain a catecholamine (probably noradrenaline) was situated in the anterior segmental nerve in the cell cluster anterior of the nephridial duct, one cell in each nerve. The axon of this cell terminates in two or more segmental ganglia; thus these neurons seem to be afferent.This work was supported by grants from the Swedish Natural Science Research Council (project no. 99-35) and the Swedish Medical Research Council (projects no. B 68-12 X-712-03 B and B 68-14 X-56-04 B).     

Ultrastructural correlates of interneuronal function in the abdominal ganglion of Aplysia californica.

The synaptic inputs and outputs of the major interneuron L10 of the abdominal ganglion of Aplysia were studied using an intracellular staining technique for the electron microscope. The sites of both the chemical synaptic input and output of L10 are localized to the dendritic arborizations that arise from the axon in the ganglion neuropil. Thus, the interneuronal functions are mediated at the dendritic processes and could occur in the absence of spiking in the axon and cell body. The sites of L10 synaptic output are presumed to be at aggregations of vesicles and mitochondria in the dendrites. The synaptic vesicle content of L10, a cholinergic neuron, with many large dense vesicles resembles that described for serotonergic cells in Aplysia, making distinction of synaptic pharmacology by ultrastructure difficult. Focal membrane specializations with a clear synaptic cleft were not observed between L10 and its large population of postsynaptic cells. In contrast, clear focal input sites were frequently found on L10. Gap junctions, sites of probable electrical coupling between L10 and other neurons, were also found. These observations are discussed as evidence that many synapses do not have focal specializations.     

Comparative study of nerve elements and their relationships with Endocrine glands and muscle retractors in Ommatophores of snails and slugs

A comparative study of the total cytoarchitectonics and structural interrelations of receptor and nerve elements at the area of receptor cell bodies, in tentacular ganglia and their digital outgrowths as well as in the lateral wall of tentacular olfactory organs of several species of terrestrial snails and slugs from different families was carried out using Golgi and Colonnier silver nitrate impregnation technique and horseradish peroxidase labeling. The presence of a peculiar cluster of intraepithelial receptor cells has been established for the first time in sensory epithelium of ommatophores. A connection of endocrine cells of the optic gland with nerve and receptor elements of tentacular ganglia was shown. Peculiarities of innervation of muscle refractors and lateral wall of ommatophores were revealed. FMRFamide-positive nerve fibers were found to participate in innervation of muscle elements of ommatophores. Neurotensin-positive and occasional serotonin-positive nerve elements also were revealed in the tentacular organs. Electron microscopic study showed the presence of complicated synaptic complexes of either convergent or divergent type and of many symmetric synaptic structures in neuropil of tentacular ganglia. Many nervous fibers and synapses contain several types of granular and agranular vesicles, which indicates possible co-localization of several bioactive substances in the same nerve elements.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 6, 2004, pp. 556–568.     

Effects of two mitosis inhibitors (Colchicine and Vinblastine) on the distribution and axonal transport of noradrenaline storage particles,studied by fluorescence and electron microscopy

Summary The lumbar sympathetic ganglia and the interganglionic interconnecting nerves of untreated rats and rats treated with Colchicine (COL) or Vinblastine (VIN) were studied with the help of the Falck-Hillarp fluorescence technique and electron microscopy. Both in untreated and drug treated rats there was a good correlation between the distribution of noradrenaline (NA) specific fluorescence and granular vesicles supporting the previous view that the granular vesicles represent the main intraneuronal NA storage sites. The granular vesicles were present both in the cell bodies—mainly in the peripheral part of the cytoplasm— and in the axons of untreated rats. After local application of COL or VIN on the ganglia there was a marked increase in fluorescence intensity and number of granular vesicles in many cell bodies. Often increased number of granular vesicles were found in the neighbourhood of the Golgi apparatus, in which region only few such vesicles are found in untreated rats. In some cell bodies high numbers of granular vesicles could be found all over the cytoplasm.When applied locally to axons the mitosis inhibitors caused a marked accumulation of fluorescence and granular vesicles—and other cell organelles like mitochondria and tubules of the endoplasmic reticulum-proximal to the site of application.A prominent feature both in cell bodies and axons of drug treated rats were large bundles of neurofilaments running through the cytoplasm. In the axons these filaments were often localized to the central part of the axon and surrounded by vesicles and tubules. Microtubules, on the other hand, which are rather numerous in cell bodies and axons of untreated rats seemed to be reduced in number after COL or VIN treatment, especially in those axons in which large amounts of subcellular organelles had accumulated.The present findings are discussed with respect to intraneuronal transport of NA and possible mechanisms behind this transport. It is suggested that the accumulation of fluorescence and granular vesicles after application of mitosis inhibitors is due to an interruption of the centrifugal transport of NA granules. The increased numbers of granular vesicles in the neighbourhood of the Golgi apparatus suggest that granular vesicles are produced in this part of the cytoplasm. This does not exclude a local formation of granular vesicles in other parts of the neuron. Furthermore, the possibility is discussed that the interruption of the transport is related to the increased number of neurofilaments and a possible decrease or disarrangement of microtubules. This discussion is based on previous suggestions that microtubules are involved in intracellular transport mechanisms and on recent findings that COL and VIN bind to proteins specific for microtubules.This study has been supported by grants from the Swedish Medical Research Council (B70-14X-2887-01; B71-14X-2887-02A; B71-14P-3262-01 A; B70-14X-2207-04; B71-14X-2207-05A; K70-40P-3045-01A), from Magnus Bergwalls Foundation, from Wilhelm and Martina Lundgrens Foundation, from the Medical Faculty, University of Göteborg.For generous supply of vinblastine (Velbe^®) we thank Eli Lilly Ltd.The skilful technical assistance of Mrs Kirsten Collin, Mrs Waldraut Hiort and Mr Pär-Anders Larsson is gratefully acknowledged.