Lack or Inhibition of Dopaminergic Stimulation Induces a Development Increase of Striatal Tyrosine Hydroxylase-Positive Interneurons |
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Authors: | Carla Letizia Busceti Domenico Bucci Gemma Molinaro Paola Di Pietro Luca Zangrandi Roberto Gradini Rosario Moratalla Giuseppe Battaglia Valeria Bruno Ferdinando Nicoletti Francesco Fornai |
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Institution: | 1. IRCCS Neuromed, Pozzilli, Italy.; 2. Department of Experimental Medicine, University “Sapienza”, Roma, Italy.; 3. Department of Functional and Systems Neurobiology, Istituto Cajal CSIC, Madrid, Spain.; 4. Department of Physiology and Pharmacology, University “Sapienza”, Roma, Italy.; 5. Department of Human Morphology and Applied Biology, University of Pisa, Pisa, Italy.; University of Chicago, United States of America, |
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Abstract: | We examined the role of endogenous dopamine (DA) in regulating the number of intrinsic tyrosine hydroxylase-positive (TH+) striatal neurons using mice at postnatal day (PND) 4 to 8, a period that corresponds to the developmental peak in the number of these neurons. We adopted the strategy of depleting endogenous DA by a 2-day treatment with α-methyl-p-tyrosine (αMpT, 150 mg/kg, i.p.). This treatment markedly increased the number of striatal TH+ neurons, assessed by stereological counting, and the increase was highly correlated to the extent of DA loss. Interestingly, TH+ neurons were found closer to the clusters of DA fibers after DA depletion, indicating that the concentration gradient of extracellular DA critically regulates the distribution of striatal TH+ neurons. A single i.p. injection of the D1 receptor antagonist, {"type":"entrez-protein","attrs":{"text":"SCH23390","term_id":"1052733334","term_text":"SCH23390"}}SCH23390 (0.1 mg/kg), the D2/D3 receptor antagonist, raclopride (0.1 mg/kg), or the D4 receptor antagonist, L-745,870 (5 mg/kg) in mice at PND4 also increased the number of TH+ neurons after 4 days. Treatment with the D1-like receptor agonist {"type":"entrez-protein","attrs":{"text":"SKF38393","term_id":"1157151916","term_text":"SKF38393"}}SKF38393 (10 mg/kg) or with the D2-like receptor agonist, quinpirole (1 mg/kg) did not change the number of TH+ neurons. At least the effects of {"type":"entrez-protein","attrs":{"text":"SCH23390","term_id":"1052733334","term_text":"SCH23390"}}SCH23390 were prevented by a combined treatment with {"type":"entrez-protein","attrs":{"text":"SKF38393","term_id":"1157151916","term_text":"SKF38393"}}SKF38393. Immunohistochemical analysis indicated that striatal TH+ neurons expressed D2 and D4 receptors, but not D1 receptors. Moreover, treatment with the α4β2 receptor antagonist dihydro-β-erythroidine (DHβE) (3.2 mg/kg) also increased the number of TH+ neurons. The evidence that DHβE mimicked the action of {"type":"entrez-protein","attrs":{"text":"SCH23390","term_id":"1052733334","term_text":"SCH23390"}}SCH23390 in increasing the number of TH+ neurons supports the hypothesis that activation of D1 receptors controls the number of striatal TH+ neurons by enhancing the release of acetylcholine. These data demonstrate for the first time that endogenous DA negatively regulates the number of striatal TH+ neurons by direct and indirect mechanisms mediated by multiple DA receptor subtypes. |
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