Neurochemical and immunocytochemical studies of catecholamine system in the brindled mouse

The Mammalian Locus Coeruleus Complex-Consistencies and Variances in Nuclear Organization

Descriptions of the nuclear parcellation of the locus coeruleus complex have been provided in approximately 80 mammal species spanning the phylogenetic breadth of this class. Within the mammalian rostral hindbrain, noradrenergic neurons (revealed with tyrosine hydroxylase and dopamine-ß-hydroxylase immunohistochemistry) have been observed within the periventricular grey matter (A4 and A6 nuclei) and parvicellular reticular nucleus (A5 and A7 nuclei), with the one exception to date being the tree pangolin, where no A4/A6 neurons are observed. The alphanumeric nomenclature system, developed in laboratory rodent brains, has been adapted to cover the variation observed across species. Cross-species homology is observed regarding the nuclear organization of noradrenergic neurons located in the parvicellular reticular nucleus (A5 and A7). In contrast, significant variations are observed in the organization of the A6 neurons of the locus coeruleus proper. In most mammals, the A6 is comprised of a moderate density of neurons, but in Murid rodents, primates, and megachiropteran bats, the A6 exhibits a very high density of neurons. In primates and megachiropterans, there is an additional moderate density of A6 neurons located rostromedial to the high-density portion. These variations are of importance in understanding the translation of findings in laboratory rodents to humans.

Rat Bone Mesenchymal Stem Cell-Derived Exosomes Loaded with miR-494 Promoting Neurofilament Regeneration and Behavioral Function Recovery after Spinal Cord Injury

Exosomes (Exo) exhibit numerous advantages (e.g., good encapsulation, high targeting efficiency, and easy to penetrate the blood-brain barrier to the central nervous system). Exosomes are recognized as prominent carriers of mRNAs, siRNAs, miRNAs, proteins, and other bioactive molecules. As confirmed by existing studies, miR-494 is important to regulate the occurrence, progression, and repair of spinal cord injury (SCI). We constructed miR-494-modified exosomes (Exo-miR-494). As indicated from related research in vitro and vivo, Exo-miR-494 is capable of effectively inhibiting the inflammatory response and neuronal apoptosis in the injured area, as well as upregulating various anti-inflammatory factors and miR-494 to protect neurons. Moreover, it can promote the regeneration of the neurofilament and improve the recovery of behavioral function of SCI rats.

Menkes disease: Oral administration of glyoxal-bis(N(4)-methylthiosemicarbazonato)-copper(II) rescues the macular mouse

BACKGROUND

Menkes disease is a copper metabolism disorder caused by mutations in ATP7A, a copper-transporting P-type ATPase. In this study, oral copper supplementation via glyoxal-bis(N(4)-methylthiosemicarbazonato)-copper(II) (CuGTSM), a lipophilic copper complex, was investigated in male hemizygous macular (Mo^Ml/y) mice, a mouse model of Menkes disease.

METHODS

CuGTSM was administered by oral gavage on postnatal days 5, 8, 11, 17, 23, and 32. The copper levels in the organs and serum, copper-dependent enzyme activities in the brain, and ceruloplasmin (Cp) activity in the serum were measured at 15 days and 3 and 8 months of age. Histological analysis of the intestines and the rotarod test were also performed.

RESULTS

CuGTSM treatment extended the lifespan of Mo^Ml/y mice and partly restored the copper concentrations and cytochrome oxidase and DBH activities in the brain; however, the rotarod test showed impaired motor performance. The treatment also increased copper concentrations and Cp activity in the serum. In suckling Mo^Ml/y mice, CuGTSM treatment transiently induced diarrhea accompanied by copper accumulation and altered villus morphology in the ileum.

CONCLUSION

Oral administration of CuGTSM extended the lifespan of Mo^Ml/y mice. Oral administration is attractive, but pharmaceutical studies are needed to reduce the adverse enteral effects.

Distribution and morphology of putative catecholaminergic and serotonergic neurons in the brain of the greater canerat, Thryonomys swinderianus

The distribution, morphology and nuclear subdivisions of the putative catecholaminergic and serotonergic systems within the brain of the greater canerat (sometimes spelt cane rat) were identified following immunohistochemistry for tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the complement of nuclear subdivisions of these systems when comparing those of the greater canerat with reports of these systems in other rodents. The greater canerat was chosen for investigation as it is a large rodent (around 2.7kg body mass) and has an average brain mass of 13.75g, more than five times larger than that of the laboratory rat. The greater canerats used in the present study were caught from the wild, which is again another contrast to the laboratory rat. While these differences, especially that of size, may lead to the prediction of significant differences in the nuclear complement of these systems, we found that all nuclei identified in both systems in the laboratory rat and other rodents in several earlier studies had direct homologs in the brain of the greater canerat. Moreover, there were no additional nuclei in the brain of the greater canerat that are not found in the laboratory rat or other rodents. It is noted that the locus coeruleus of the laboratory rat differs in appearance to that reported for several other rodent species. The greater canerat is phylogenetically distant from the laboratory rat, but still a member of the order Rodentia. Thus, changes in the nuclear organization of these systems appears to demonstrate a form of constraint related to the phylogenetic level of the order.

Extensive degeneration of catecholaminergic neurons to scrapie agent 87V in the brains of IM mice

Scrapie is a degenerative disease of the central nervous system of sheep and goats. The causative agent has been passaged to a number of laboratory species, including mice and hamster. Amyloid plaque formation and vacuolation, the signs of senile dementia, are found in the brains of mice infected with 87V scrapie agent. Dopamine (DA) and norepinephrine (NE) concentrations in the brains of scrapie-infected mice were measured with high-performance liquid chromatography-electrochemical detector (HPLC-ECD). A significant decrease in NE level was exhibited in all regions tested, whereas the level of DA decreased significantly only in cerebral cortex. Immunohistochemistry was used to examine immunoreactive catecholamine neurons in substantia nigra and locus ceruleus using antisera against tyrosine hydroxylase (TH). The population of TH-immunoreactive neurons in the substantia nigra and locus ceruleus were significantly decreased in scrapie-infected mice compared to controls. These data suggest that both the noradrenergic and dopaminergic system are sensitive to the action of scrapie agent 87V and that changes in the catecholamine levels in the brains of scrapie-infected mice may contribute to some of the clinical symptoms of the diseases, such as ataxia and apraxia.

Neurochemical and histochemical evidence for an abnormal catecholamine metabolism in the cerebral cortex of the Long-Evans Cinnamon rat before excessive copper accumulation in the brain

Distributions of norepinephrine (NE), dopamine (DA) and its metabolites in the cerebral cortex in Long-Evans Cinnamon (LEC) rats, an animal model of Wilson's disease, aged 4, 10 (in the early stage of the disease) and 20 weeks (in the advanced stage of the disease) were determined to elucidate the effect of the abnormal copper (Cu) metabolism observed in the LEC rat on the brain catecholamine metabolism. NE depression as well as excessive accumulations of DA and facilitation of the DA catabolic pathway to its acidic metabolites were observed in the cerebral cortex of the LEC rat at 4 and 10 weeks of age. Furthermore, immunohistochemical analysis of the cuproenzyme dopamine-beta-hydroxylase (DBH) showed lower antigenicity of DBH in the cortical neurons in the cerebral cortex of LEC rats aged 4 weeks than in control rats. These results suggest that neurochemical disturbances involved in an abnormal catecholamine metabolism may occur in the cerebral cortex of the LEC rat before excessive Cu accumulation.

Heterotypic sprouting of serotonergic forebrain fibers in the brindled mottled mutant mouse

The brindled mottled mouse has a mutation on the X-chromosome which causes alterations in copper metabolism. One role for copper is as a cofactor for dopamine-beta-hydroxylase (DBH), the enzyme that converts dopamine to norepinephrine (NE). This may explain the fact that the hemizygous males have low concentrations of NE, as well as high concentrations of 5-hydroxyindoleacetic acid (5-HIAA) in the brainstem and forebrain. The present study quantified serotonin (5-HT) immunoreactive fibers in the cerebral cortex and striatum of hemizygous males and control littermates on postnatal (P) days 7, 10, 12 and 14. The density of 5-HT immunoreactive fibers was measured using a digitized imaging system in conjunction with darkfield microscopy. Measurements of 5-HT innervation showed an age-dependent increase in density of 5-HT immunoreactive fibers in all layers of the cerebral cortex, with fiber density in brindled mice approximately 70% greater than controls by P14. High performance liquid chromatography confirmed the increased concentrations of 5-HT and 5-HIAA, and the low concentration of NE, in several regions. We believe that these results are an example of heterotypic sprouting of 5-HT neurons, similar to that observed in neonatal rats given 6-hydroxydopamine (6-OHDA). If so, these data provide the first description of 5-HT heterotypic sprouting in mice, and the first description of 5-HT heterotypic sprouting resulting from a natural disease state, rather than an experimentally induced lesion.