Likewise, every effort was made to avoid unnecessary stress and pain to

the experimental animals. The number of animals was kept to the minimum necessary to test the concept. The experimental animals used in this study were Swiss albino mice (Mus musculus) of approximately 26–30 g, Wistar rats (Rattus norvegicus) of 150–200 g, and frog (Lithobates catesbeianus). The toxicity of A. paulensis venom was evaluated by determining the 50% lethal dose (LD50) in mice, the dose able to kill 50% of animals tested. Four experimental groups were tested with different doses of venom: 20, 25, 30 and 40 μg/g of mice (n = 5/group). The venom was dissolved in 100 μL saline solution (150 mM NaCl) and injected by i.p. route. The control group (n = 5) was injected with saline. The lethality rate of animals was observed 48 h after inoculation of venom or saline. At the end of the experiment, the surviving animals were euthanized with an

ABT 199 overdose of sodium pentobarbital (about 75 mg/kg). The values for the lethality assay and their confidence limits were calculated by Probit analysis ( Finney, 1971), using the software BioStat 5.8.4 version 2009. The venom of the A. paulensis spider was evaluated for its ability to induce behavioral and physiological changes in mice. All animals used in the lethality assay were observed during the first hour of the experiment, and the symptoms were identified as described in Table 1. All mice utilized in the lethality assay were dissected and their heart, lung, kidney, liver and spleen were removed, fixed in 10% buffered formalin and embedded in paraffin (Prophet et al., 1992). Histological sections (4 mm thick) were stained with hematoxylin eosin (HE) selleckchem and analyzed under a light microscope (Axioskop-2, Zeiss, Germany). The tissues of animals injected with A. paulensis venom were compared with the tissues of animals injected with saline solution, and any changes were considered. The nociceptive behavior was evaluated by the intradermal Urease injection in mice. The assay was preformed similar to formalin test, in which two phases can be observed: Phase I (0–10 min) is referred as the acute phase and the Phase II (10–50 min)

is associated with local release of endogenous mediators, which generate local inflammatory response (for review, see Le Bars et al., 2001). Twenty-eight mice (n = 5–6/group) were used. Three experimental groups were subcutaneously injected through intraplantar route into the left hind-paw with different doses of crude venom (5, 10 and 20 μg/paw). The venom was dissolved in saline solution (150 mM NaCl), and the injection volume was 50 μL. The positive control mice received 50 μL of 2.5% formalin and the negative one 50 μL saline solution through the same route of administration. After injections, each mouse was placed in a transparent glass cage, and the amount of time the animal licked, bit or shook the injected paw was determined between 0 and 10 min (first phase) and 10 and 50 min (second phase).