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Pharmacological characterization and autoradiographic localization of dopamine receptors in the rat adrenal medulla.
No full textThe pharmacological profile and the anatomical localization of dopamine D1-like and D2-like receptors were studied in sections of rat adrenal medulla, with radioligand binding and autoradiographic techniques, respectively. [3H]([R]-(+)-chloro-2,3,4,5-tetrahydro-5-phenyl-1 H-3benzazepin-al hemimaleate) (SCH 23390) was used as a ligand for dopamine D1-like receptors and [3H]spiperone was used as a ligand for dopamine D2-like receptors. Radioligand binding and light microscope autoradiography did not show specific [3H]SCH 23390 binding in sections of rat adrenal medulla. This suggests that rat adrenal medulla does not express dopamine D1-like receptors. [3H]Spiperone was specifically bound to sections of rat adrenal medulla. The binding was time-, temperature- and concentration-dependent, with a dissociation constant (Kd) of 1.05 nM and a maximum density of binding sites (Bmax) of 100.2 +/- 3.8 fmol/mg tissue. The pharmacological profile of [3H]spiperone binding to rat adrenal medulla was similar to that displayed by neostriatum, which is known to express dopamine D2 receptors. Light microscope autoradiography showed the accumulation of specifically bound [3H]spiperone as silver grains within sections of adrenal medulla. Silver grains were found primarily over the cellular membrane of chromaffin cells. The above data indicate that chromaffin cells of the rat adrenal medulla express dopamine receptors belonging to the dopamine D2 receptor subtype. These receptors are probably involved in the modulation of catecholamine release from chromaffin cells, as documented by functional studies
Microanatomical localization of dopamine receptor protein immunoreactivity in the rat cerebellar cortex
No full textDopamine (DA) receptor subtype localization was investigated in rat cerebellar cortex using immunohistochemical techniques with antibodies raised against D1-D5 receptor protein. A faint D1 receptor protein immunoreactivity was developed in molecular and Purkinje neurons layers. D2 receptor protein immunoreactivity was found primarily in cerebellar white matter followed by molecular and granular layers and Purkinje neurons. Antibodies against D2S receptor protein were localized in molecular layer and to a lesser extent, in granular layer. A few Purkinje neurons displayed a faint D2S receptor protein immunoreactivity. D3 receptor protein immunoreactivity was observed primarily in molecular and in Purkinje neurons layers of lobules 9 and 10. A faint D3 receptor protein immunoreactivity was also localized in Purkinje neurons and to a lesser extent, in molecular and granular layers of cerebellar lobules 1-8. D4 receptor protein immunoreactivity was found in cerebellar white matter. A pale immunostaining was also visualized in molecular layer. D5 receptor protein immunoreactivity was localized primarily in molecular and Purkinje neurons layers and to a lesser extent, in granular layer and in white matter. The above results indicate that rat cerebellar cortex expresses the DA receptor subtypes so far identified. Purkinje neurons, which are the only efferent neurons of cerebellum, are richest in DA receptor protein immunoreactivity. This suggests that dopaminergic neurotransmission may modulate efferent inputs from cerebellum. The localization of the majority of D2 and D4 and of a faint D5 protein receptor immunoreactivity in cerebellar white matter suggests that these receptors may be presynaptic and transported axonall
Compounds related to cytochalasans. Some reactions of the cycloadduct of maleic anhydride and ethyl sorbate
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Pharmacological characterization and autoradiographic localization of a putative dopamine D3 receptor in the rat kidney
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SENSITIVITY AGEING OF THE LIMBIC DOPAMINERGIC SYSTEM: A REVIEW
No full textThe limbic system includes the complex of brain centres, nuclei and connections that provide the anatomical substrate for emotions. Although the presence of small amounts of dopamine (DA) in several limbic structures has been recognized for a long time, for many years it was thought that limbic DA represented a precursor of noradrenaline in the biosynthetic pathway of catecholamines. More recent evidence has shown that limbic centres and nuclei are supplied with a dopaminergic innervation arising from the ventral tegmental area (field A10) and in smaller amounts from the mesencephalic A9 field. The dopaminergic limbic system is sensitive to ageing. Parameters of dopaminergic neurotransmission (DA levels, biosynthetic and catabolic markers and DA receptors) undergo age-related changes which depend on the structure and species investigated and are characterized mainly by a decline of different parameters examined. In this paper, the influence of ageing on DA biosynthesis, levels, metabolism and receptors are reviewed in laboratory rodents, monkeys and humans as well as in cases of Alzheimer's disease and Parkinson's disease. The possibility that changes of dopaminergic neurotransmission markers in the limbic system are associated with cognitive impairment and psychotic symptoms affecting the elderly is discussed. Better knowledge of dopaminergic neurotransmission mechanisms in the so-called physiological ageing and in senile dementia may provide new insights in the treatment of behavioural alterations frequently occurring in old age
Microanatomical localization of dopamine receptor protein immunoreactivity in the rat cerebellar cortex.
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Age-related changes of glial fibrillary acidic protein immunoreactive astrocyets in the rat cerebellar cortex.
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