Altered acetylcholine release in the hippocampus of dystrophin-deficient mice.
Mild cognitive impairments have been described in one-third of patients with Duchenne muscle dystrophy (DMD). DMD is characterized by progressive and irreversible muscle degeneration caused by mutations in the dystrophin gene and lack of the protein expression. Previously, we have reported altered concentrations of α7- and β2-containing nicotinic acetylcholine receptors (nAChRs) in hippocampal membranes of dystrophic (mdx) mice. This suggests that alterations in the central cholinergic synapses are associated with dystrophin deficiency. In this study, we examined the release of acetylcholine (ACh) and the level of the vesicular ACh transporter (VAChT) using synaptosomes isolated from brain regions that normally have a high density of dystrophin (cortex, hippocampus and cerebellum), in control and mdx mice at 4 and 12months of age. ACh release evoked by nicotinic stimulation or K(+) depolarization was measured as the tritium outflow from superfused synaptosomes preloaded with [(3)H]-choline. The results showed that the evoked tritium release was Ca(2+)-dependent and mostly formed by [(3)H]-ACh. β2-containing nAChRs were involved in agonist-evoked [(3)H]-ACh release in control and mdx preparations. In hippocampal synaptosomes from 12-month-old mdx mice, nAChR-evoked [(3)H]-ACh release increased by 57% compared to age-matched controls. Moreover, there was a 98% increase in [(3)H]-ACh release compared to 4-month-old mdx mice. [(3)H]-ACh release evoked by K(+) depolarization was not altered, while the VAChT protein level was decreased (19%) compared to that of age-matched controls. In cortical and cerebellar preparations, there was no difference in nAChR-evoked [(3)H]-ACh release and VAChT levels between mdx and age-matched control groups. Our previous findings and the presynaptic alterations observed in the hippocampi of 12-month-old mdx mice indicate possible dysfunction of nicotinic cholinergic synapses associated with dystrophin deficiency. These changes may contribute to the cognitive and behavioral abnormalities described in dystrophic mice and patients with DMD.
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Parames
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Coletta-Yudice
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Nogueira
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Nering de Sousa
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Hayashi
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
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Lima-Landman
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil; Laboratory of Pharmacology and Toxicology, Amazon Biotechnology Center, Manaus, Amazonas, Brazil.
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Lapa
Department of Pharmacology, Section of Natural Products, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil. Electronic address: csouccar@unifesp.br.
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Souccar
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D002531:Cerebellum / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D016189:Dystrophin / Q000172:deficiency* / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018733:Nicotinic Antagonists / Q000494:pharmacology; D011189:Potassium Chloride / Q000378:metabolism; D011978:Receptors, Nicotinic / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D050494:Vesicular Acetylcholine Transport Proteins / Q000378:metabolism
D000109:Acetylcholine; D016189:Dystrophin; D018733:Nicotinic Antagonists; D011189:Potassium Chloride; D011978:Receptors, Nicotinic; D050494:Vesicular Acetylcholine Transport Proteins; C493460:Slc18a3 protein, mouse
[(3)H]-ACh release; dystrophin; hippocampus; mdx mouse; nicotinic acetylcholine receptor; vesicular ACh transporter