Retrograde axonal transport after radioactive serotonin injections into the olfactory bulb: a biochemical analysis of transported radioactive material

Effects of agricultural activities on hydrochemistry in the Shiyang River Basin, China

Agricultural water accounts for more than 80% of the available water in arid areas. Agricultural activities have a great impact on surface water and groundwater. If the impact of agricultural activities on hydrochemistry is not prevented, the risk of water quality change in arid areas may be greatly intensified. Based on the hydrochemical data of the whole Shiyang River Basin from April 2014 to October 2019, this paper analyzes the impact of agricultural activities on hydrochemistry in the basin. The results show that (i) in the middle and lower reaches of farmland with high intensity of agricultural activities, the ion concentration of groundwater in summer and autumn is significantly higher than that in winter and spring due to the influence of irrigation; (ii) the runoff ion concentration in the backflow of the river reaches recharged by irrigation water is significantly higher than that of other reaches; (iii) due to strong evaporation, different types of reservoirs will lead to an overall increase in ion concentration, which is more obvious in plain reservoirs and river tail lakes. In addition, the reservoirs have a certain removal effect on nitrates.

Hydrochemical characteristics and irrigation suitability of surface water in the Syr Darya River, Kazakhstan

The surface water hydrochemistry of the Syr Darya River in Kazakhstan was investigated at 39 locations to analyze regional hydrochemical characteristics and evaluate the irrigation suitability of the studied regions. The cations in the surface water are mainly Na⁺, Ca²⁺, and Mg²⁺, while the anions are mainly SO₄^2-. The main hydrochemical type is Ca-Mg-SO₄-Cl. From the perspective of natural factors, the hydrochemical characteristics in the study area are derived from the dual effects of rock weathering and evaporation-concentration; however, the influence of anthropogenic factors include industrial and agricultural production near the river and the inflow of urban domestic sewage on the hydrochemical characteristic is also present. The irrigation suitability evaluation of the surface water based on SAR, Na% and KI showed that the majority of the water is suitable for irrigation, and from the TDS content analysis, 71.43% of the samples are in a critical state, indicating that the influence of TDS concentration on irrigation suitability cannot be ignored. The results have practical significance for maintaining the sustainable use of water resources in the Syr Darya River.

Serotonergic retinopetal projections from the dorsal raphe nucleus in the mouse demonstrated by combined [(3)H] 5-HT retrograde tracing and immunolabeling of endogenous 5-HT

The present study demonstrated a direct serotonergic retinopetal projection in the mouse stemming from the lateral portion of the dorsal raphe nucleus bilaterally. A double-labeling technique was employed combining: (1) radioautography and retrograde axonal tracing following intraocular injection of [(3)H] 5-HT and (2) immunocytochemical identification of endogenous 5-HT. Radiolabeled neurons were only observed within the dorsal raphe nucleus and were always double-labeled with the 5-HT antibody. The radiolabeling appeared to be specific resulting from the retrograde transport of a radioactive 5-HT derivative product following uptake of the neurotransmitter by intraretinal terminals.

Long-term isolation of Wistar rats alters brain monoamine turnover, blood corticosterone, and ACTH

In this work, we investigated neurochemical parameters in the brain of male Wistar rats after isolation times (13 weeks) longer than those previously reported with this strain: a large majority of animals became muricidal under these conditions. Changes in monoamines turnover in hippocampus, cortex, and cerebellum and, in the blood, ACTH, and corticosterone were investigated. Monoamine turnover was analysed using two different approaches: first, by measuring neurotransmitter and metabolite levels and second, by measuring rate of accumulation of the precursor after decarboxylase. Both methods revealed a significant increase in catecholamine turnover in the three regions studied after the 13-week isolation; in contrast, only a modest elevation of 5-hydroxytryptophan accumulation was obtained in cortex and cerebellum of isolated rats. We also observed a decrease in corticosterone levels in blood concomitant with an increase of ACTH.

Tracing specific transmitter pathways in the rat CNS: combination of [3H]serotonin retrograde labelling with immunocytochemical detection of endogenous transmitters

Selective retrograde labelling with [3H]serotonin ([3H]5-HT) can be used to identify serotonergic cell bodies after specific [3H]5-HT uptake by the corresponding nerve terminals. In the present study, we demonstrate that autoradiography of this [3H]5-HT radiolabelling can be combined with immunocytochemical detection of endogenous serotonin, GABA or substance P on the same tissue section. The midbrain raphe serotonergic projections to the olfactory bulb and the spinal projections of medullary serotonergic nuclei were investigated. The specificity of retrograde labelling with [3H]5-HT was confirmed by immunoreactivity of the radiolabelled cells for serotonin, using an antiserum specific for formaldehyde-fixed serotonin. After spinal injections of [3H]5-HT, many retrogradely labelled cells in the medullary raphe were immunopositive for substance P, and a few for GABA. These results are in agreement with the available information on the co-existence of putative transmitters in the spinal projections of caudal raphe neurons. Therefore, autoradiography of [3H]5-HT retrograde labelling combined with immunocytochemistry offers a possibility to test the specificity of transmitter-selective retrograde labelling, to identify transmitter-defined neuronal interactions and to investigate the projection fields of multitransmitter containing neurons.

[3H]-serotonin retrograde labelling in serotonergic fibers

Autoradiography, following retrograde axonal transport with [3H]-serotonin (10(-4) M) was used to identify, selectively, the serotonergic neurons of medullary raphe that innervate the spinal cord. In combination with this technique, immunocytochemical detection of endogenous serotonin showed some raphe magnus cell bodies immunostained by 5-HT antibodies and [3H]5-HT radiolabelled. Serotonergic fibers of lateral and dorsolateral funiculus of ligated spinal cord were also characterized following retrograde axonal transport with 10(-4) M [3H]-serotonin. At the ultrastructural level, mainly myelinated, although unmyelinated labelled fibers were also identified as swollen axons. Clusters of large membranous organelles, predominantly mitochondria, some dense lamellar bodies, multivesicular bodies and lysosomes accumulated on the distal segment of the ligation. Autoradiographic reaction was always observed to be very intense and silver grains overlapped mainly mitochondria (41%) and clusters of membranous organelles (37%). However, smooth endoplasmic reticulum seemed to be devoid of silver grains. From our results, serotonergic myelinated spinal fibers were labelled after uptake-retrograde axonal transport with [3H]5-HT. Mitochondria and membrane organelles could convey tritiated compounds derived from [3H]-serotonin uptake towards the serotonergic cell bodies.

Serotonergic projections to the spinal cord but not those to the olfactory bulb also contain substance P. A combined immunocytochemical and autoradiographic study following retrograde axonal transport of [3H]serotonin labeled products

Co-localization of substance P with serotonin in raphe projection neurons was studied by combining substance P immunocytochemistry and autoradiography following uptake and retrograde axonal transport of [3H]serotonin and/or its products from target areas. In this study, two central pathways in the rat were investigated: the serotonergic projections of the midbrain raphe to the olfactory bulb and those of the medullary raphe that innervate the thoracic spinal cord. Two hours after pargyline pretreatment, injections of 10(-4) M [3H]serotonin were made either into the olfactory bulb or into the spinal cord and respectively 24 or 60 h thereafter, rats were administered with colchicine. After a 24 h survival time, the paraformaldehyde fixed brains were investigated for substance P immunocytochemistry and then treated for light and electron microscopy autoradiography. Combining both methods, we can define on the same tissue sections at least three labeled neuronal populations: substance P immunolabeled neurons, radiolabeled neurons and doubly immuno-radiolabeled neurons. In the midbrain raphe cells as well as in the olfactory bulb nerve terminals, two kinds of labeled profiles were detected: substance P immunoreactive profiles and radiolabeled ones. The radiolabeled cell bodies of the midbrain raphe (403 counted cells) were never reactive to substance P antibodies. Moreover, they were distributed caudally to substance P stained perikarya. In contrast, in the medullary raphe, of the 336 radiolabeled cell bodies 162 were stained after substance P antibody treatment. They represent about 48% of the serotonin radiolabeled neurons projecting to the thoracic spinal cord, where a great number of varicosities were observed immunolabeled, radiolabeled and doubly immuno-radiolabeled in the dorsal horn. At the ultrastructural level, cell bodies and dendritic processes were also doubly labeled. Both labelings were observed over the cytoplasm and some organelles or perikarya. These observations provide a morphological basis to support the hypothesis that substance P can occur within some but not all serotonergic neurons and raise questions about the expression of this peptide in these systems as well as the modes of interaction of these transmitter molecules.

Benzodiazepine receptor and neurotransmitter studies in the brain of suicides

The characteristics of benzodiazepine binding sites (affinity, number heterogeneity) were studied on frozen sections of hippocampus of 7 suicides and 5 controls subjects, using biochemical and autoradiographic techniques. 3H flunitrazepam was used as ligand, clonazepam and CL 218,872 as displacing agents. Some neurotransmitters or their derivatives (GABA, catecholamines, hydroxy-indols) were evaluated quantitatively in parallel in the hippocampal tissue by liquid chromatography. We observed mainly an increase in the Ki of CL 218,872 subtype I binding sites in suicides, (7.48 +/- 1.7 to 17.24 +/- 1.7 nM, P less than 0.01), (m +/- SEM) and an increase in % of type I binding sites (30 +/- 4.2 to 42 +/- 2.5, P = 0.01). Among neurotransmitters, only norepinephrine differed significantly between controls and suicides (11.34 +/- 1.9 to 24.34 ng/g tissue, P = 0.02).