Contents lists available at ScienceDirect Acta Histochemica journal homepage: www.elsevier.com/locate/acthis Acute infection with an avirulent strain of Toxoplasma gondii causes decreasing and atrophy of nitrergic myenteric neurons of rats Débora de Mello Gonçales Sant’Ana a , Marcelo Biondaro Gois b, ⁎ , Catchia Hermes-Uliana c , Letícia Sarturi Pereira-Severi a , Emily Martins Baptista d , Luana Colognese Mantovani d , Aristeu Vieira da Silva e , Eduardo José de Almeida Araújo f a State University of Maringá, Department of Biosciences and Physiopathology, Maringá, PR, Brazil b Federal University of Reconcavo of Bahia, Santo Antonio de Jesus, BA, Brazil c Federal University of Mato Grosso do Sul, Coxim, MS, Brazil d University Paranaense, Umuarama, PR, Brazil e State University of Feira de Santana, Department of Biological Sciences, Feira de Santana, BA, Brazil f State University of Londrina, Department of Histology, Londrina, PR, Brazil ARTICLE INFO Keywords: Enteric nervous system NADPH-diaphorase Nitric oxide Neuroplasticity Toxoplasmosis ABSTRACT In the enteric nervous system (ENS), nitrergic neurons produce and use nitric oxide (NO) as an inhibitory motor neurotransmitter in response to parasitic infections, including those caused by Toxoplasma gondii. However, damage to the host caused by NO has been reported by various authors, and the role of NO in protection or cytotoxicity continues to be extensively studied. In this study, nitrergic neurons were investigated in the myenteric plexus of the jejunum and the distal colon of rats infected with 500 oocysts of the M7741 strain of T. gondii. Ten rats were randomly assigned into a control group (CG) and infected group (IG; received 500 sporulated oocysts of T. gondii orally). After 24 h, the rats were euthanized, and samples of the jejunum and distal colon were obtained and processed for NADPH-diaphorase histochemical analysis. Quantitative and morphometric analysis of the nitrergic neurons in whole mounts containing the myenteric plexus was performed. There was a numeric reduction of nitrergic neurons per mm 2 in both jejunum and distal colon. The remaining nitrergic neurons suffered atrophy in the areas of the cell body and nucleus, which resulted in a decrease in cytoplasm. Thus, we conclude that an avirulent strain of T. gondii in a short time causes neuroplastic changes in the small and large intestine of rats. 1. Introduction Toxoplasma gondii is an obligate intracellular parasite. Felidae are the definitive hosts, and eliminate oocysts into the environment through their feces. Other homeothermic species become intermediate hosts by ingesting oocysts present in contaminated water or food (Dubey, 2010). During natural infections, T. gondii initially crosses the intestinal epithelium, disseminates into the deep tissues, and crosses biological barriers (Barragan and Sibley, 2003). However, the effects of infection are dependent on the strain and genotype of the parasite and on the host as well (Liesenfeld, 2002; Weiss and Kim, 2007). Enterocytes infected with T. gondii undergo morphological and physiological changes, and trigger an innate immune response mediated by pro-inflammatory cytokines and cytotoxic molecules such as nitric oxide (NO), through various cell types (Buzoni-Gatel and Werts, 2006). Neurons and enteric glial cells produce NO by the expression of nitric oxide synthase (NOS) (Sharkey and Savidge, 2014), which can be detected by histochemical assay for NADPH- diaphorase (NADPH-d) (Grozdanovic et al., 1992; Scherer and Singler et al., 1983). The neuronal isoform of NOS (nNOS) plays a central role in the elimination of parasites from the gastrointestinal tract (Halliez and Buret, 2015) and contributes to the homeostasis. The gastrointestinal tract motility, secretion, and blood flow is regulated by a division of the autonomic nervous system known as enteric nervous system (ENS), located in the wall of the gastrointestinal tract. The ENS detects the physiological condition of the gastrointest- inal tract, integrates information about it and provides outputs to control gut movement (Furness, 2006; Góis et al., 2016a). Thus, pathogens can be detected in the intestinal lumen and it can trigger diarrhoea. Nitric oxide synthase (NOS) is found in 29% of all myenteric neurons of the small intestine. Ninety percent of these nitrergic neurons http://dx.doi.org/10.1016/j.acthis.2017.04.008 Received 26 January 2017; Received in revised form 22 April 2017; Accepted 27 April 2017 ⁎ Corresponding author. E-mail address: marcelobiondaro@gmail.com (M.B. Gois). Acta Histochemica xxx (xxxx) xxx–xxx 0065-1281/ © 2017 Elsevier GmbH. All rights reserved. Please cite this article as: Sant’Ana, D.d.M.G., Acta Histochemica (2017), http://dx.doi.org/10.1016/j.acthis.2017.04.008