SEARCH · PubMed Health

Results for “RADIOAUTOGRAPHY”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49Linked to original sources

PubMed1980

Biological labeling of very low density lipoproteins with cholesteryl linoleyl ether and its fate in the intact rat.

In vitro labeling of very low density lipoproteins (VLDL) with radioactive cholesteryl linoleyl ether, an analog of cholesteryl linoleate, was studied. The protocol which gave the highest efficiency and seemed least injurious to the final product included: (1) sonication of the labeled cholesteryl ether with partially delipidated high density lipoproteins (HDL); (2) transfer of the labeled lipids to VLDL in the presence of lipoprotein-deficient human serum; (3) reisolation of the VLDL by ultracentrifugation. Under optimal conditions 70% of the added labeled lipid was recovered with HDL and 60% were transferred from HDL to VLDL. The labeled cholesteryl linoleyl ether was shown to comigrate with the protein of VLDL on agarose gel electrophoresis. In negatively stained preparations, the labeled VLDl and its unlabeled counterpart had similar appearance. The in vitro labeled VLDL was injected into rats and was cleared from the circulation with a t1/2 comparable to endogenously labeled VLDL. More than 80% of the injected dose was recovered in the liver between 3 and 48 h after injection of VLDL labeled with [3H]cholesteryl linoleyl ether of which 91-97% were in the ether form. On radioautography of fixed frozen sections of liver the bulk of the radioautographic reaction was associated with the cytoplasm of hepatocytes. When the VLDL had been labeled also with [14C]cholesteryl linoleate only 35% of injected dose was present in the liver at 3 h, of which 87% was in unesterified form. The distribution of the labeled cholesteryl linoleyl ether, 3-48 h after injection, expressed as per cent of injected dose per organ was 0.7-1.5 in spleen, 0.2-0.5 in lung, 0.1 in heart and 0.2-0.4 in adrenal. The main advantage of the presently described approach in which a nondegradable analog of cholesteryl ester was introduced into VLDL by a biological procedure is the possibility to study the role of various organs to take up circulating cholesteryl ester, especially in species in which LDL is produced from VLDL.

Animals↗

PubMed1978

Excision repair in ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome, and Bloom's syndrome after treatment with ultraviolet radiation and N-acetoxy-2-acetylaminofluorene.

Excision repair of damage due to ultraviolet radiation, N-acetoxy-2-acetyl-aminofluorene and a combination of both agents was studied in normal human fibroblasts and various cells from cancer prone patients (ataxia telangiectasia, Fanconi's anemia, Cockayne syndrome and Bloom's syndrome). Three methods giving similar results were used: unscheduled DNA synthesis by radioautography, photolysis of bromodeoxyuridine incorporated into parental DNA during repari, and loss of sites sensitive to an ultraviolet endonuclease. All cell lines were proficient in repair of ultraviolet and acetoxy acetylaminofluorene damage and at saturation doses of both agents repair was additive. We interpret these data as indicating that the rate limiting step in excision repair of ultraviolet and acetoxy acetylaminofluorene is different and that there are different enzyme(s) working on incision of both types of damages.

Ataxia Telangiectasia↗

PubMed1980

DNA excision repair in human cells treated with ultraviolet radiation and 7,12-dimethylbenz[a]anthracene 5,6-oxide.

Excision repair was measured in normal human and xeroderma pigmentosum group C cells treated with 7,12-dimethylbenz[a]-anthracene 5,6-oxide and with ultraviolet radiation by the techniques of unscheduled DNA synthesis, repair replication, a modification of bromodeoxyuridine photolysis employing the dye Hoechst 33258 and 365 nm radiation, and endonuclease-sensitive sites assay. Radioautography and repair replication showed that in normal cells the magnitude of repair after a saturation dose of epoxide (approx. 10 microM) to be 0.1-0.2 that after a saturating ultraviolet dose (20 J/m2 at 254), though survival data showed that both doses gave nearly similar killings. Repair was of the long-patch type and repair kinetics after the epoxide treatment were similar to ultraviolet. After a combined treatment with both agents, unscheduled synthesis in normal cells was more than additive, although, considering the experimental errors, these data and those of repair replication are consistent with additivity. The epoxide did not inhibit loss of sites sensitive to the ultraviolet endonuclease. However, after a combined treatment to xeroderma pigmentosum cells there was appreciably less unscheduled synthesis than for the sum of both treatments and the epoxide inhibited the loss of nuclease-sensitive sites. We interpret the data to indicate that there are different rate-limiting steps in the removal of the ultraviolet and the epoxide damages, and that the residual repair activity in xeroderma pigmentosum cells is accomplished by different, not just fewer, enzymes than in normal cells.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1980

Identification of neighbouring protein pairs in the rat liver 40-S ribosomal subunits cross-linked with dimethyl suberimidate.

(1) The 40-S ribosomal subunits of rat liver were treated with a bifunctional cross-linking reagent, dimethyl suberimidate. Cross-linked protein-protein dimers were separated by two-dimensional acrylamide gel electrophoresis. The stained cross-linked complexes within the gel were radioiodinated without the elution of proteins from the gel and were cloven into the original monomeric protein constituents by ammonolysis. The proteins in each dimer were finally identified by two-dimensional acrylamide gel electrophoresis of the cloven monomeric proteins, followed by radioautography of the stained gel. (2) The molecular weights of cross-linked complexes were determined by SDS-polyacrylamide gel electrophoresis and were compared with those of their constituent proteins. (3) The following dimers were proposed from these results: S3-S12 (S3 or S3a-S11), S4-S12 (S3b-S11, S5-S7 (S4-S6), S5-S22 (S4-S23 or S24), S6-S8 (S5-S7), S8-S16 (S7-S18), S17-S21 (S16--S19) and S22A-S22B (S23-S24), designated according to our numbering system [1]. The designations according to the proposed uniform nomenclature [2] are described in parentheses.

Acetates↗

PubMed1985

Receptors for insulin-like growth factor-I (IGF-I) in myocardial capillary endothelium of the intact perfused heart.

Isolated intact, beating hearts were perfused with HPLC-pure [125]-IGF-I (1 ng/ml) alone or [125]-IGF-I (1 ng/ml) plus varying concentrations of unlabeled IGF-I (10-3,000 ng/ml) or unlabeled insulin (1,000-100,000 ng/ml). After 1 min of perfusion with peptides, the hearts were rapidly fixed, sectioned and analyzed for radioautographic [125I] grain counts. Greater than 90% of [125I] grains were shown to represent intact [125I]-IGF. Maximal grain counts over capillaries occurred after perfusion with [125I]-IGF-I alone and decreased in a dose-dependent manner when unlabeled IGF-I was coperfused. Coperfusion of [125I]-IGF-I with unlabeled insulin also decreased 125I grains over capillaries but less potently than unlabeled IGF-I. EM radioautography demonstrated that [125I]-IGF-I grains were localized over capillary endothelial cells. Thus, specific IGF-I receptors are present in the capillary endothelium of the intact heart and have properties similar to IGF-I receptors in cultured capillary endothelial cells.

Adipose Tissue↗

PubMed1987

The formation and stability of the hypusine containing protein in Chinese hamster ovary cells.

Hypusine-containing protein identified as eukaryote initiation-translation factor 4D was labeled with [14C]spermidine in logarithmically growing Chinese hamster ovary cells. Radioautography of the cellular proteins separated by polyacrylamide gel electrophoresis showed the label in a single protein of 18000 Mr. Time course analysis showed that this protein remained undegraded for up to 72 hours after its synthesis. Radioactivity present in the amino acid hypusine, isolated after acid hydrolysis, remained constant during the same period of time. These results indicate that the hypusine-containing protein has a long half-life.

Animals↗

PubMed1975

Distribution of olivocerebellar fibers demonstrated by a radioautographic tracing method.

The method of injecting radioactive amino acids for the marking of neurons and the demonstration of their terminals by means of radioautography has been applied to the olivocerebellar projection. After injections in the olive, labeled fibers were observed in the molecular layer of the cerebellar cortex. The projections were distributed in specific regions of the cerebellum, depending on the position of the injections within the nucleus. A comparison of that topographical arrangement with Brodal's chart of olivocerebellar distribution indicates a close correspondence. In addition, the olivocerebellar climbing fibers terminate as a series of strips oriented perpendicularly to the long axes of the folia. In all regions observed so far, the strips of the projection alternate with empty spaces of the same width. It is postulated that another group of climbing fibers originating outside the olive interdigitate with the olivocerebellar fibers.

Animals↗

PubMed1975

Radioautographic study of the rat brain after injection of [1,2-3H]corticosterone.

Cryostat sections of the central nervous system of adrenalectomized male rats injected with [3H]corticosterone were examined by radioautography. One hour after the injection, radioactivity was found to be selectively concentrated in specific neurons of the septum, the hippocampal complex (precommissural hippocampus, cornu Ammonis, gyrus dentatus, subiculum), the indusium griseum, the amygdala and in certain areas of the cortex. In the hippocampus, the pyramidal neurons in fields CA1 and CA2 of the cornu Ammonis and the granule neurons of the gyrus dentatus contained more radioactivity than did other regions of the brain. Most of the silver grains were localized in the nuclei of labeled cells. The topographic distribution of corticosterone-concentrating neurons shows that the hormonal target sites in the central nervous system are mainly extrahypothalamic.

Adrenalectomy↗

PubMed1975

Serotonin nerve terminals in adult rat neocortex.

Axonal processes which take up and retain exogenous tritiated serotonin ([3H]5-HT) have been demonstrated in the fronto-parietal cortex of adult rats, by means of high resolution radioautography. Prolonged topical superfusion with relatively high concentrations of ([3H]5-HT allowed detection of a maximal number of axonal reactions in the upper 3 layers of cortex. Comparison of results obtained from normal rats and animals pretreated with 6-hydroxydopamine or bearing midbrain raphe lesions established the specificity of this labeling. All reactive axons seemed to arise from the serotonin nerve cell bodies in groups B7 and B8 of Dahlström and Fuxe15. In electron microscope radioautographs, the serotonin fibers appeared as tenuous, naked axonal processes (0.1-0.5 mum in diameter) exhibiting small enlargements (0.7 mum in mean diameter) spaced at frequent intervals (1-3 mum). These boutons contained occasional mitochondria, small, round, agranular 'synaptic' vesicles and large granular vesicles. With axons, [3H]5-HT was concentrated in the boutons, and to a much lesser extent in connecting segments. This reactive pattern resembled that revealed by the fluorescence technique for endogenous serotonin. Preferential accumulations of the tracer by mitochondria and vesicular organelles indicated that these elements could sequester exogenous serotonin. Large granular vesicles were not necessarily visible in random thin sections of the labeled varicosities, and thus could not serve as the unique criterion for electron microscopic identification of 5-HT terminals. Moreover, these organelles are known to be present in other types of nerve endings. Topometric analysis of serial thin sections nevertheless demonstrated that large granular vesicles were potentially detectable in every 5-HT containing bouton, and also enabled extrapolation of their average number at 7 per varicosity. This low number makes it unlikely that large granular vesicles primarily represent storage sites. They could rather serve as a carrier for particle-bound enzymes essential to the local metabolism of serotonin or its precursors. A very small fraction of the serotonin varicosities exhibited the membrane differentiations of typical synaptic terminals. Extensive sampling in serial thin sections revealed junctional complexes in only 5% of labeled boutons, as opposed to 50% of unlabeled nerve endings in the surrounding neuropil. The data do not preclude the possibility that other monoaminergic neurons also share similar characteristics. It is probable that endogenous serotonin can be liberated from all axonal varicosities including those lacking strictu senso synaptic relationships. The overall configuration and ultrastructural features of cortical serotonin fibers suggest intrinsic dynamic properties which could assume particular significance in terms of function, plasticity and regrowth.

Animals↗

PubMed1975

Axoplasmic transport in the toad Bufo marinus.

The rate and course of axoplasmic transport from the eighth dorsal root ganglion cell bodies into the sciatic nerve of the toad Bufo marinus were studied. Concentrated tritiated proline was hydraulically injected into a surgically exposed dorsal root ganglion of animals maintained at 19 +/- 0.5 degrees C. At postinjection intervals of 1, 6, and 10 h, the animals were sacrificed and the dorsal root, ganglion, and sciatic nerve were removed bilaterally. The dorsal roots and peripheral nerves were cut into 3 mm segments measured from the ganglion. In some experiments all tissues were prepared for liquid scintillation counting techniques. In others the ganglion and every fifth 3 mm nerve segment were fixed in Bouin's fixative for radioautography, and the remaining tissue segments were prepared for liquid scintillation counting methods. Scintillation counts (counts/min) of consecutive segments along the labeled nerve were plotted against distance (mm) for each animal. Examination of these profiles showed a peak of radioactivity in the injected ganglion for each animal that was followed distally by an abrupt drop in the adjacent segments of the nerve. Radioactivity remained relatively stable in subsequent segments forming a plateau and then dropped to baseline levels forming a wavefront in the distal portion of the peripheral nerves of the 6 and 10 h toads. Movement of this wavefront during the 6 to 10 h time interval provided evidence for an axoplasmic flow rate of about 120 mm/day. Radioautographs of the ganglion and representative segments along the sciatic nerve were examined with both bright- and dark-field microscopy. Accumulations of silver grains were observed overlying the injected ganglion cell bodies and labeled axons of the nerve. Values for the number of silver grains/unit area were obtained from dark-field radioautographs of the nerve segments through the use of a computer-microscope system. The relative amount of radioactivity present in the axons was thereby demonstrated. Radioautographic data confirmed the axoplasmic flow rate of about 120 mm/day determined by liquid scintillation counting methods for the bulk of radioactive materials transported at this fast rate. In addition, the evaluation of radioautographic data suggests that an even faster flow rate of 185-215 mm/day may exist for a small portion of the labeled materials transported in the axon.

Animals↗

PubMed1976

Protein metabolism in transected peripheral nerves of the crayfish.

The significance of the protein metabolism in crayfish peripheral nerve was studied in relation the ability of crayfish motor axons to survive for over 200 days following axotomy. In contrast to frog peripheral nerves, the crayfish nerves appear to more closely resemble ganglia in their profiles of synthesis expressed on sodium dodecyl sulfate (SDS) gels, and have higher incorporation rates of [3H]leucine into protein than ganglia. Since anisomycin inhibits over 95% of protein synthesis in crayfish peripheral nerve, it was concluded that this local protein synthesis was dependent upon a eukaryotic ribosomal mechanism. Radioautography of isolated nerves reveals newly synthesized proteins in glial sheaths, and also within the axoplasm of large motor fibers. Based upon the data available at present, a hypothesis that the glia surrounding the axons are responsible for the local protein synthesis, and that some of these newly synthesized proteins are transported into the axon, is presented. Transection of crayfish peripheral nerves proximal to the neuron cell bodies produced a more than two-fold increase in [3H]leucine incorporation, but no significant changes in labeling profiles of the proteins on SDS gels. The data suggest that while an active local protein synthesis may be necessary for the maintenance of several crayfish motor axons, it is not a sufficient condition.

Animals↗

PubMed1976

Separately developing axonal uptake of 5-hydroxytryptamine and norepinephrine in the fetal ileum of the rabbit.

Uptake of 5-hydroxytryptamine (5-HT) by adult and fetal rabbit's ileum was studied. The adult myenteric plexus accumulated tritium when incubated with tritiated 5-HT. However, in addition to labeled 5-HT, tritiated 5-hydroxyindole acetic acid and, when monoamine oxidase (MAO) was inhibited, 5-HT-o-glucuronide were found in the tissue. Two uptake processes differing in affinity could be defined. Only the high affinity process was saturable. Fetal ileum took up tritiated 5-HT but glucuronidation did not occur when MAO was inhibited. The uptake of tritiated 5-HT by the fetal ileum was due to a single, saturable, temperature sensitive (Q10 at 27-37 degress C = 2.4) process inhibited by ouabain. It was identical to the high affinity uptake found in adult tissue. This specific high affinity uptake could be found as early as the 16th day of gestation, 5-8 days before uptake of norepinephrine (NE) begins. Light and electron microscope radioautography revealed that the uptake of 5-HT was primarily into axons and a characteristic structure called the expanded process, both in the myenteric plexus. Both contained dense-cored vesicles. Axons were not labeled by tritiated NE until after 24 days and the expanded process was never labeled by tritiated NE. This study shows that uptake of 5-HT is a property of distinct system of axons in the mammalian myenteric plexus which develops prior to adrenergic axons during ontogeny.

Animals↗

PubMed1977

Efferent connections of the septal area in the rat: an analysis utilizing retrograde and anterograde transport methods.

Experiments were performed by either retrograde (horseradish peroxidase histochemistry) or anterograde ([3H]leucine radioautography) transport methods to determine the efferent connections of the septum in the rat. It was observed that the dorsal septum projects to the lateral preoptic area, lateral hypothalamus, periventricular hypothalamus and midline thalamus. Fibers from the ventral half of the septum project topographically to the hippocampal formation, thalamus, hypothalamus and midbrain. Specifically, neurons located along the midline in the vertical limb of the diagonal band project through the dorsal fornix to all CA fields of the dorsal hippo campus and adjacent subicular cortex. Other fibers from this region project through the stria medullaris to the medial habenular nucleus and anteromedial nuclhe pars posterior of the medial mammillary nucleus. Cells located immediately lateral to the midline in the vertical limb of the diagonal band project through the medial part of the fimbria to all CA fields of the posterior hippocampus and adjacent subicular cortex. Other fibers which originate from this region project through the stria medullaris to both the medial and lateral habenular nuclei and the paratenial nucleus of the thalamus, and through the medial forebrain bundle to the pars posterior of the medial mammillary nucleus. Cells located in the intermediolateral septum project through the lateral part of the fimbria to all CA fields of the ventral hippocampus and adjacent subicular and entorhinal cortices. These cells also send fibers through the stria medullaris to the lateral habenular nucleus and mediodorsal thalamic nucleus. Other axons arising from these cells descend through the medial forebrain bundle to terminate in a region dorsal to the interpeduncular nucleus. Fibers from the most lateral part of the ventrl septum (i.e., bed nucleus of the anterior commissure) project through the stria terminalis to the ventral subiculum. In addition, cells located in the horizontal limb of the diagonal band project massively to the pars posterior of the medial mammillary nucleus and the ventral tegmental area, and amygdala.

Animals↗

PubMed1977

Glycoproteins are modified in the axon of R2, the giant neuron of Aplysia californica, after intra-axonal injection of [3H]N-acetylgalactosamine.

We have found evidence that mechanisms exist in the axon by which proteins, originally synthesized in the cell body, can be modified. Incorporation of [3H]N-acetyl-D-galactosamine into macromolecules was studied in the axon of R2, the giant identified neuron of the abdominal ganglion of Aplysia. The precursor sugar, injected directly into the major axon in the right connective, labeled both glycoproteins and glycolipids. These macromolecules were associated with membranes and at least 90% of the incorporated radioactivity could be sedimented by centrifugation at 105,000 X g. Radiocutography of injected axons with the light microscope showed that most of the silver grains were located over the axon rather than over other tissues in the right connective. Grains appeared over a variety of axonal components, but quantitative electron microscopic radioautography revealed that vesicles were the only organells significantly labeled. Disco polyacrylamide gel electrophoresis in sodium dodecyl sulfate (SDS) of the membrane fraction resolved [5-(3)H]glycoprotein components. These membrane glycoproteins ranged in apparent molecular weight from 20,000 to 160,000 daltons and could be digested by pronase. Only one component had a mobility similar to that of a glycoprotein found in the axon after injection of the cell body. Incorporation of [3H]N-acetylgalactosamine into axonal glycoprotein was unaffected by anisomycin, a potent inhibitor of protein synthesis in Aplysia, and therefore presumably occurred on already existing polypeptide chains. We conclude that these were synthesized in the cell body and exported into the axon where they were modified by the addition of sugar.

Acetylgalactosamine↗

PubMed1977

Uptake of serotonin by intrinsic neurons of the myenteric plexus grown in organotypic tissue culture.

The myenteric plexus contains axons, not found elsewhere in the peripheral nervous system, which are distinguished by a specific, high affinity transport system for serotinin (5-HT). This study was undertaken to determine the location of the cell bodies of origin of these axons. Vagotomy decreased uptake of [3H]5-HT and tritiated norepinephrine ([3H]NE) by the myenteric plexus. However, while examination by histofluorescence revealed the presence of descending vagal adrenergic fibers, no evidence was found for the presence or accumulation of 5-HT above a vagal ligature. Vagus nerves thus contain adrenergic but not serotonergic axons. The gut was also denervated of all extrinsic axons by growth of intestinal explants in organotypic tissue culture for 3 weeks. Uptake of [3H]5-HT persisted while uptake of [3H]NE was lost. Light and quantitative electron microscopic radioautography revealed that, as in intact gut, the elements of the cultures responsible for uptake of [3H]5-HT were axons distinguished by varicosities containing large dense cored vesicles. In conclusion, these experiments establish that the mammalian gut contains intrinsic neurons which selectively take up 5-HT. The capacity of these neurons for 5-HT uptake may be influenced by the vagus nerves.

Animals↗

PubMed1977

Efferent connections of the hippocampal formation in the rat.

In this investigation the projections of the hippocampal formation to the septal area and hypothalamus were studied in the rat with the combined use of 3H-amino acid radioautography and horseradish peroxidase histochemistry. The results indicate that all of the fibers which project to the hypothalamus and the majority of fibers which project to the septum arise from the subicular cortex and not from hippocampal pyramidal cells. The projection to both of these areas are topographically organized along the longitudinal axis of the hippocampal formation. Specifically, fibers from subicular cortical cells situated at the septal end of the hippocampal formation which project through the medial part of the dorsal fornix terminate in the dorsomedial quadrant of the lateral septal nucleus and in the dorsal portion of the pars posterior of the medial mammillary nucleus. Fibers from progressively more posteroventral levels of the hippocampal formation which project through more lateral portions of the dorsal fornix and fimbria terminate in progressively lateral and ventral quadrants of the lateral septal nucleus and in progressively more ventral portions of the pars posterior. Concerning the specific origin of the fornix system, fibers from only the prosubiculum and subiculum project through both the pre- and postcommissural fornix. Hippocampal pyramidal cells from all CA fields have a restricted projection through the precommissural fornix and terminate in the caudal half of the septum while the presubiculum projects solely through the postcommissural fornix. The medial corticohypothalamic tract (MCHT) was found to arise from cells located in anterior ventral levels of the subicular cortex. Fibers from this tract appeared to be distributed throughout the pericellular region of the entire ventromedial extent of the hypothalamus from the level of the suprachiasmatic nucleus through the level of the medial mammillary nucleus. In this way, the mammillary bodies receive input from the subicular cortex via two routes: the descending column of the fornix and the MCHT.

Animals↗

PubMed1977

Thalamic projections of the hippocampal formation: evidence for an alternate pathway involving the internal capsule.

Experiments were performed using [3H]leucine radioautography and horseradish peroxidase histochemistry to determine the origin and distribution of the projection from the hippocampal formation to the thalamus in the rat. The results confirm recent findings that postcommissural fornix fibers which project to the anterior thalamus arise exclusively from the subicular cortex and not from hippocampal pyramidal cells. A second significant feature of this pathway is that it arises from cells situated in the deepest layer of subicular cortex at dorsal and posterior levels of the hippocampal formation. Thirdly, one component of this projection involves the internal capsule instead of the fornix. Fibers which pass through this fiber bundle arise from the lateral portion of the subicular complex adjacent to field CA1 of the hippocampus (i.e., prosubiculum) and terminate bilaterally throughout the anteromedial thalamic nucleus. In contrast, fibers from the region of subicular cortex adjacent to the retrosplenial cortex (i.e., presubiculum) pass through the postcommissural fornix and terminate in the ventral portion of the anteroventral thalamic nucleus. Fibers from central portions of the subicular complex (i.e., subiculum) project through both the internal capsule and postcommisural fornix and terminate in the anteromedial and adjacent ventral portion of the anteroventral thalamic nuclei. Fibers which project to the dorsal portion of the anteroventral thalamic nucleus arise from adjacent portions of retrosplenial cortex and project through the internal capsule.

Animals↗

PubMed1978

The topographical distribution of serotoninergic terminals in the spinal cord of the cat: quantitative radioautographic studies.

In vitro uptake of labeled serotonin (5-HT) has allowed the radioautographic detection of serotoninergic fibers in the cat spinal cord at thoracic and lumbar levels. The specificity of labeling was ensured by the conditions of incubation ([3H]5-HT was 10(-7) M) and by test control experiments with concomitant 10(-6) M NA or 2 X 10(-6) M fluoxetine which led respectively to an unmodified or a negative radioautographic pattern. Macroscopic radioautography with [14C]5-HT gave the framework for analysis of 5-HT innervation at this level which appeared dense in the grey matter and more scattered in white matter except in the periphery. In the grey matter labeled structures appeared at histological level as randomly oriented fibers. They displayed enlargements which were identified by electron microscopy as varicosities (mean diameter 0.7 micrometer) containing clear and large granular vesicles. To estimate the density of 5-HT varicosities in grey matter, semi-automatic counting was performed on histological radioautographs, using an image analyzer. Maximal concentrations of boutons were found in the periependymal region, the sympathetic lateral column, the whole dorsal horn and the motor neuron area of ventral horn. In a densely innervated region, the number of boutons was estimated to be at least 2.65 X 10(6)/cu.mm. In white matter, labeled fibers were longitudinally oriented in the periphery and obliquely in other regions, except in the dorsal funiculus, where they were nearly absent. Previous histofluorescence and biochemical data are confirmed and completed by the results of this approach which displays several advantages in resolution, sensitivity and possibilities of automated quantification. Moreover owing to the dynamic abilities of the radioautographic method, the spinal cord provides a good model for the study of the properties (namely the axonal flow) and the functions of the serotoninergic neurons.

Animals↗