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ABSTRACT The use of gaseous inhalation agents for animal euthanasia offers rapid action due to easy access to the arterial circulation. The neuroprotective property of postmortem brain tissue collection was investigated using isoflurane and carbon dioxide (CO2) on the serum bioindicators of sodium and potassium. Serum samples were collected from 3 groups of animals (n=8) and donated to this study, previously approved by the Ethics Committee on the Use of Animals (CEUA 173/2020). The serum groups analyzed were named isoflurane, CO2 and cannabidiol (CBD/CO2). The results demonstrated that the three groups had elevated potassium levels compared to the control group (*, p<0.05), indicating hyperkalemia, while no difference was observed in serum sodium. Furthermore, the CO2 and CBD/CO2 groups differed significantly from the isoflurane group (#, p<0.05), which had the highest level of hyperkalemia. These findings contribute to our understanding of the physiological effects of different euthanasia methods on the biochemical profiles of animals. In conclusion, the use of CO2 is recommended as a euthanasia method for collecting brain tissue due to the lowest impact on potassium levels.

RESUMO O uso de agentes inalatórios gasosos para a eutanásia de animais oferece ação rápida devido ao fácil acesso à circulação arterial. A propriedade neuroprotetora para a coleta de tecido cerebral post mortem foi investigada utilizando-se isoflurano e dióxido de carbono (CO2) sobre os bioindicadores séricos de sódio e potássio. Amostras de soro foram coletadas de três grupos de animais (n=8) e doadas para este estudo, previamente aprovado pelo Comitê de Ética no Uso de Animais (CEUA 173/2020). Os grupos de soro analisados foram denominados isoflurano, CO2 e canabidiol (CBD/CO2). Os resultados demonstraram que os três grupos apresentaram níveis elevados de potássio em comparação ao grupo controle (*, P<0,05), indicando hipercalemia, enquanto nenhuma diferença foi observada no sódio sérico. Além disso, os grupos CO2 e CBD/CO2 diferiram significativamente do grupo isoflurano (#, P<0,05), que apresentou o maior nível de hipercalemia. Esses achados contribuem para a compreensão dos efeitos fisiológicos dos diferentes métodos de eutanásia sobre os perfis bioquímicos dos animais. Como conclusão, recomenda-se o uso de CO2 como método de eutanásia para coleta de tecido cerebral devido ao menor impacto sobre os níveis de potássio.

Resumo

Plathymenia reticulata Benth has an anti-inflammatory effect and is capable of neutralizing the neuromuscular blockade induced by Bothrops jararacussu or Crotalus durissus terrificus venoms, probably by precipitating venom proteins (an effect caused by plant tannins). The present study aimed to evaluate the mutagenic activity of P. reticulata by using the Salmonella mutagenicity assay (Ames test) and the micronucleus test in CHO-K1 cells. P. reticulata extract concentrations of 2.84, 5.68, 11.37, and 19.90 mg/plate were assayed by the Ames test using TA97a, TA98, TA100 and TA102 bacterial strains, with (+S9) and without (-S9) metabolic activation. Concentrations of 5, 1.6 and 0.5 ìg/mL of P. reticulata extract were used for the micronucleus test. P. reticulata extract was mutagenic to TA98 (-S9) and showed signs of mutagenic activity in TA97a and TA102 (both -S9) strains. Micronucleus test CBPI values showed that the endogenous metabolic system increased the number of viable cells when compared to the non-activated samples and the micronucleus frequency increased when the cells were treated in the absence of S9. We concluded that P. reticulata extract may present direct mutagenic properties.

Resumo

The crude venom of Bothrops jararacussu (Bjssu) is known to induce muscular paralysis in vitro. Many studies have shown that various substances, including heparin, neutralize the damage caused by snake venom. In the present study, the ability of heparin (Hep) and commercial bothropic antivenom (CBA) to neutralize neuromuscular effects of Bjssu venom, at different time-points, was analyzed. Mouse phrenic nerve-diaphragm preparation was used through a conventional myographic technique, following five different protocols: Group 1 was incubated with Bjssu (40 µg/mL) without any other treatment; Groups 2 and 3 were pretreated with heparin (1 µL/mL) and CBA (120 µL/mL), respectively, for 15 minutes before venom addition; Group 4 after 50 percent neuromuscular blockade induced by Bjssu crude venom received 1 µL/mL of heparin while Group 5 received a mixture of Hep:CBA:Bjssu. Control preparations (Tyrode) were treated with Hep and CBA (mean ± SEM; n = 3-6). After 120 minutes of venom incubation, Group 1 preparations presented twitch-tension of 12 ± 2 percent. However, in Groups 2 and 3, the neutralizations were 92 ± 1.9 percent and 81 ± 6 percent, respectively. The heparin addition, after 50 percent neuromuscular blockade by Bjssu, produced 40 ± 6 percent muscular response after 120 minutes of incubation. Hep:CBA:Bjssu mixture displayed a protective effect of 84 ± 10 percent against venom action. In conclusion, heparin and commercial bothropic antivenom efficiently neutralized the neurotoxic effects caused by B. jararacussu crude venom, even at different incubation time-points.

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The hydroalcoholic extract of Casearia gossypiosperma Briquet (Flacourtiaceae) was standardized for the first time through quality control procedures including pharmacognostic methods, fingerprint chromatograms, defined amounts of marker substances and physicochemical characteristics. The pharmacological activity of C. gossypiosperma (Cg) hydroalcoholic extract was assayed by a traditional in vitro test, which involved irreversible neuromuscular blockade induced by Bothrops jararacussu (Bjssu) venom (60 ìg/mL) in mouse phrenic nerve-diaphragm preparations. Bjssu venom blocked muscle activity for 26 (± 2.0) minutes (n = 6). Cg extract (0.1 mg/mL) induced changes on the baseline muscle activity without impairing the muscle function and inhibited 87.6% (± 1.8) (n = 6) of the Bjssu venom-induced blockade. Both flavonoids (0.624 g%) and polyphenols (4.63 g%) from the extract were spectrophotometrically quantified. Therefore, the present study confirms the antibothropic activity of Cg extract, supporting the ethnomedical use of Casearia sp. in the treatment of snakebite victims.

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In the present study, manganese (Mn2+), a neuromuscular blocker with pre and postsynaptic actions, was used to verify the neurotoxicity and myotoxicity induced by Crotalus durissus terrificus (Cdt) and Bothrops jararacussu (Bjssu) venoms in biventer cervicis preparations (BCp). Preparations pretreated with 0.66 and 1.6mM Mn2+ did not affect Cdt venom-induced blockage nor change KCl-induced contracture but partially reduced ACh-induced contracture. However, both Mn2+ concentrations partially hindered Bjssu venom-induced blockage after washing the preparations with Krebs solution, and only 1.6mM Mn2+ preparations significantly recovered ACh-induced contracture. The effect of Cdt venom myotoxicity on contractile responses was different from that of Bjssu venom myotoxicity. Pretreatment with 1.6mM Mn2+ partially reduced muscle damage percentage and creatine kinase (CK) activity (U/l) induced by both venoms. In conclusion, Mn2+ interfered in ACh-induced contracture of the nicotinic receptor; did not prevent Cdt venom neurotoxicity but partially reduced its myotoxicity in vitro due to the stabilizing action of this venom on the sarcolemmal membrane; and partially attenuated myotoxicity and neuromuscular blockage induced by Bjssu venom. The Mn2+ dual action (pre and postsynaptic) is useful to study snake venoms since most of them present one or both of these actions; besides, Mn2+ allowed recovering coherent interpretation of experimental versus clinical results.

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The pharmacological effects of Bothrops neuwiedi pauloensis venom on mouse phrenic nerve-diaphragm (PND) preparations were studied. Venom (20 mug/ml) irreversibly inhibited indirectly evoked twitches in PND preparations (60 ± 10 percent inhibition, mean ± SEM; p<0.05; n=6). At 50 mug/ml, the venom blocked indirectly and directly (curarized preparations) evoked twitches in mouse hemidiaphragms. In the absence of Ca2+, venom (50 mug/ml), produced partial blockade only after an 80 min incubation, which reached 40.3 ± 7.8 percent (p<0.05; n=3) after 120 min. Venom (20 mug/ml) increased (25 ± 2 percent, p< 0.05) the frequency of giant miniature end-plate potentials in 9 of 10 end-plates after 30 min and the number of miniature end-plate potentials which was maximum (562 ± 3 percent, p<0.05) after 120 min. During the same period, the resting membrane potential decreased from - 81 ± 1.4 mV to - 41.3 ± 3.6 mV 24 fibers; p<0.01; n=4) in the end-plate region and from - 77.4 ± 1.4 to -44.6 ± 3.9 mV (24 fibers; p<0.01; n=4) in regions distant from the end-plate. These results indicate that B. n. pauloensis venom acts primarily at presynaptic sites. They also suggest that enzymatic activity may be involved in this pharmacological action.(AU)

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Numerous plants are used as snakebite antidotes in Brazilian folk medicine, including Casearia sylvestris Swartz, popularly known as guaçatonga. In this study, we examined the action of a hydroalcoholic extract from C. sylvestris on the neuromuscular blockade caused by bothropstoxin-I (BthTX-I), a myotoxin from Bothrops jararacussu venom, in mouse isolated phrenic nerve-diaphragm (PND) preparations. Aqueous (8 and 12 mg/ml, n=4 and 5, respectively) and hydroalcoholic (12 mg/ml, n=12) extracts of the leaves of C. sylvestris caused facilitation in PND preparations followed by partial neuromuscular blockade. BthTX-I (20 mg/ml, n=4) caused 50% paralysis after 65±15 min (mean ± S.E.M). Preincubation (30 min at 37°C) of BthTX-I (20 mg/ml, n=4) with a concentration of the hydroalcoholic extract (4 mg/ml) that had no neuromuscular activity, such as the control (n=5), prevented the neuromuscular blockade caused by the toxin. This protection may be mediated by compounds such as flavonoids and phenols identified by thin-layer chromatography and colorimetric assays