microplus. Three enzymes, called EST-1, EST-2 and EST-5, occurred in larvae and were classified as AChEs based on assays with inhibitors. The aim of this study was to determine the effect of the n-hexane extract of C. serrata on AChE activity in larvae R. microplus as well as in the brain structures, frontal cortex, striatum and hippocampus of Wistar rats. Plant material of C. serrata (leaves and stems) was collected in Porto Alegre, Rio Grande do Sul, Brazil, in December

2009 and January 2010. The plant was identified by Sérgio Bordignon (Departamento de Botânica, Centro Universitário La Salle). The voucher check details specimen (ICN 124883) was deposited in the Herbarium of the Universidade Federal do Rio Grande do Sul. Air dried and powdered plant material (200 g) was processed by maceration with n-hexane [1:10 (w/v)]. Solvent exchanges were performed until the material become colorless. The extract was then evaporated to dryness under reduced BI 6727 cell line pressure, treated with acetone and subsequently filtered and evaporated, resulting an extract rich in chromenes and free of epicuticular waxes and other undesirable compounds. The n-hexane extract of C. serrata was thoroughly solubilized in ethanol (90%) and final concentrations

of 1.5, 3 and 6 mg/mL were obtained. Previous studies demonstrated that ethanol at the final concentration employed did not induce lethality in the larvae of R. microplus ( Gonçalves et al., 2007). R. microplus ticks of a susceptible reference strain (Mozzo strain) were provided by Instituto de Pesquisas Veterinárias Desidério Finamor. Engorged females of R. microplus were collected from infested cattle, washed with water and dried in paper towel. These females were incubated at 27 °C and 70–80% relative humidity for 14 days Levetiracetam to obtain eggs. For assays, 10-day-old larval ticks

were used. Pools of 100 mg of R. microplus larvae were homogenized in 10 volumes (1:10) of ice-cold 50 mM phosphate buffer (pH 7.0) containing 0.5% Triton-X 100, and homogenate was centrifuged at 2500 × g for 10 min at 4 °C. The resulting supernatants were used as the enzyme source. AChE activity was determined by slight modifications of the colorimetric method described by Ellman et al. (1961) and Baxter et al. (1999) using acetylthiocholine iodide (ATChI, 1 mM) as substrate. The n-hexane extract of C. serrata (final concentrations 1.5, 3 and 6 mg/mL) was incubated at 25 °C for 60 min with the enzyme source. Absorbance was measured at 412 nm, and AChE activity was estimated through differences in dA/min. Each sample was assayed in triplicate.