Enteric dysfunctions in experimental Parkinson's disease: Alterations of excitatory cholinergic neurotransmission regulating colonic motility in rats

Matteo Fornai, Carolina Pellegrini, Luca Antonioli, Cristina Segnani, Chiara Ippolito, Elisabetta Barocelli, Vigilio Ballabeni, Gaia Vegezzi, Zainab Al Harraq, Fabio Blandini, Giovanna Levandis, Silvia Cerri, Corrado Blandizzi, Nunzia Bernardini, Rocchina Colucci

Research output: Contribution to journalArticlepeer-review

Abstract

Parkinson's disease is frequently associated with gastrointestinal symptoms, mostly represented by constipation and defecatory dysfunctions. This study examined the impact of central dopaminergic denervation, induced by injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle, on distal colonic excitatory cholinergic neuromotor activity in rats. Animals were euthanized 4 and 8 weeks after 6-OHDA injection. In vivo colonic transit was evaluated by radiologic assay. Electrically induced and carbachol-induced cholinergic contractions were recorded in vitro from longitudinal and circular muscle colonic preparations, whereas acetylcholine levels were assayed in the incubation media. Choline acetyltransferase (ChAT), HuC/D (pan-neuronal marker), muscarinic M2 and M3 receptors were assessed by immunohistochemistry or western blot assay. As compared with control rats, at week 4, 6-OHDA-treated animals displayed the following changes: decreased in vivo colonic transit rate, impaired electrically evoked neurogenic cholinergic contractions, enhanced carbachol-induced contractions, decreased basal and electrically stimulated acetylcholine release from colonic tissues, decreased ChAT immunopositivity in the neuromuscular layer, unchanged density of HuC/D immunoreactive myenteric neurons, and increased expression of colonic muscarinic M2 and M3 receptors. The majority of such alterations were also detected at week 8 post 6-OHDA injection. These findings indicate that central nigrostriatal dopaminergic denervation is associated with an impaired excitatory neurotransmission characterized by a loss of myenteric neuronal ChAT positivity and decrease in acetylcholine release, resulting in a dysregulated smooth muscle motor activity, which likely contributes to the concomitant decrease in colonic transit rate.

Original languageEnglish
Pages (from-to)434-444
Number of pages11
JournalJournal of Pharmacology and Experimental Therapeutics
Volume356
Issue number2
DOIs
Publication statusPublished - Feb 1 2016

ASJC Scopus subject areas

  • Pharmacology
  • Molecular Medicine

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