RESUMO
BACKGROUND: Semen cryopreservation is essential in animal breeding programs for improving the availability of genetic resources from animals with high breeding value. OBJECTIVE: To evaluate the addition of Brazil nut extract as a replacement for egg yolk in bovine semen cryopreservation. MATERIALS AND METHODS: Semen was collected from five Nelore bulls and cryopreserved with the addition (treatments) of 0, 25, 50, 75, or 100% Brazil nut extract in the cryoprotectant medium. After thawing, spermatic cells were evaluated for morphology, plasma membrane integrity, spermatic kinetics, and in vitro fertilization. The experimental design was in randomized blocks, and the data were submitted to regression analysis. RESULTS: The minor-type and total defects, and plasma membrane integrity were affected (P < 0.05) as a function of egg yolk substitution with Brazil nut extract. There was a significant effect (P < 0.05) of Brazil nut extract addition on the spermatic kinetics and cleavage rate. CONCLUSION: The addition of Brazil nut extract in the cryoprotective medium as a substitute of egg yolk for freezing bovine semen negatively affects sperm quality and fertility.
Assuntos
Bertholletia/química , Criopreservação/veterinária , Crioprotetores , Extratos Vegetais , Preservação do Sêmen , Animais , Bovinos , Crioprotetores/farmacologia , Gema de Ovo , Masculino , Melhoramento Vegetal , Extratos Vegetais/farmacologia , Sêmen , Análise do Sêmen , Preservação do Sêmen/veterinária , Motilidade dos Espermatozoides , EspermatozoidesRESUMO
BACKGROUND: Semen freezing is of great importance for animal production because it allows the use and the rapid diffusion of the genetic material from economically important animals. OBJECTIVE: To evaluate the effect of açai (Euterpe oleracea; Arecaceae family) extract addition to the semen cryopreservation diluent on the morphology, sperm motility parameters, and plasma membrane integrity of spermatozoa. MATERIALS AND METHODS: The ejaculates, obtained from five bulls with low performance on semen freezing, were fractionated and distributed according to the experimental group. The control samples did not have açaí extract added, whereas to the treated groups were added 5, 10, 15 or 20 mg ml-1 of açaí extract into the semen diluent. The sperm morphology was evaluated with a formalin-saline-buffered solution. The plasma membrane integrity was evaluated by the epifluorescent test, while the cellular kinetics was assessed by an automated analysis of the spermatic movement. RESULTS: The sperm defects showed a linearly decreasing effect (P < 0.05) with the addition of different concentrations of açaí extract. The plasma membrane integrity was higher (P < 0.05) after the açaí addition to the cryopreservation diluent. There was no significant effect (P > 0.05) of the açaí extract on the kinetics of spermatozoa. CONCLUSION: The addition of açaí extract to the cryopreservation diluent provided better preservation of the structural integrity of the sperm plasma membrane in the bull's semen with low tolerance to the cryopreservation process.
RESUMO
Determination of the chemical composition in the body and carcass of ruminants is important for both nutritional requirement studies and the meat industry. This study aimed to develop equations to predict the body and carcass chemical composition of hair sheep using the chemical composition of body parts, carcass measurements and shrunk BW as predictors. A database containing 107 individual records for castrated male hair sheep ranging from 24 to 43 kg BW was gathered from two body composition studies. The empty body, carcass and body parts were analyzed for water, ash, fat and protein contents (%). The body parts used to estimate body and carcass composition were fore leg, hind leg and 9-11th rib section. The carcass measurements used were leg length, thoracic circumference, hind circumference, hind width, thoracic width, thoracic depth and chest width. Each model performance was evaluated using a leave-one-out cross-validation. Multiple regression analysis considering the study as a random effect revealed that body parts in association with carcass measurements were significant for predicting the chemical composition in the body of castrate male sheep. However, the use of the chemical composition of hind leg produced the best models for predicting the ash and fat contents in the empty body, whereas the water and protein contents in the empty body were better predicted when using the chemical compositions of 9-11th rib section and fore leg, respectively. Multiple regression analysis also revealed that most body parts were suitable for predicting the carcass composition, except for 9-11th rib section whose chemical composition did not produce significant prediction equations for ash and protein carcass contents. The use of the chemical composition of hind leg in association with carcass measurements produced the best models for predicting the water and fat contents in the carcass, while the ash and protein contents in the carcass were better predicted when using the chemical composition of fore leg. In conclusion, precision, accuracy and goodness-of-fit of the equations drove the selection of the chemical composition of hind leg and carcass measurements in a multivariate approach, as the most suitable predictors of the chemical composition of the body and carcass of hair sheep. However, the chemical composition of fore leg may be used as well. The developed equations could improve the accuracy of the empty body and carcass composition estimations in sheep, optimizing the estimation of nutrient requirements, as well as the carcass quality evaluation for this species.
Assuntos
Tecido Adiposo , Corpo Humano , Animais , Composição Corporal , Peso Corporal , Masculino , Carne/análise , Análise de Regressão , OvinosRESUMO
The transport of myo-inositol is the main mechanism for the maintenance of its high intracellular levels. We aimed to measure the mRNA and protein levels of myo-inositol cotransporters in the sciatic nerve (SN) and dorsal root ganglia (DRG) during experimental diabetes. Streptozotocin-induced (STZ; 4, 8, and 12 weeks; 65 mg/kg; ip) diabetic rats (DB) and age-matched euglycemic (E) rats were used for the analysis of mRNA and protein levels of sodium myo-inositol cotransporters 1, 2 (SMIT1, SMIT2) or H+/myo-inositol cotransporter (HMIT). There was a significant reduction in the mRNA levels for SMIT1 in the SN and DRG (by 36.9 and 31.0%) in the 4-week DB (DB4) group compared to the E group. SMIT2 was not expressed in SN. The mRNA level for SMIT2 was up-regulated only in the DRG in the DB4 group. On the other hand, the protein level of SMIT1 decreased by 42.5, 41.3, and 44.8% in the SN after 4, 8, and 12 weeks of diabetes, respectively. In addition, there was a decrease of 64.3 and 58.0% of HMIT in membrane and cytosolic fractions, respectively, in the SN of the DB4 group. In the DRG, there was an increase of 230 and 86.3% for SMIT1 and HMIT, respectively, in the DB12 group. The levels of the main inositol transporters, SMIT1 and HMIT, were greatly reduced in the SN but not in the DRG. SMIT-1 was selectively reduced in the sciatic nerve during experimental STZ-induced diabetes.
Assuntos
Transporte Biológico Ativo/fisiologia , Diabetes Mellitus Experimental/metabolismo , Gânglios Espinais/metabolismo , Inositol/metabolismo , RNA Mensageiro/metabolismo , Nervo Isquiático/metabolismo , Animais , Western Blotting , Masculino , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Estreptozocina , Regulação para CimaRESUMO
Essential oils (EO) are volatile liquids responsible for the aroma of plants. Pterodon polygalaeflorus seeds have received widespread use in folk medicine for the treatment of inflammatory diseases. For this reason and because Pterodon polygalaeflorus seeds have great EO content, which is frequently pharmacologically active, the present study aimed to evaluate the antinociceptive effect of EO from Pterodon polygalaeflorus (EOPPgfl) and its acute toxic effects. The EEOPPgfl sample, which was extracted by steam distillation of the seeds, had a yield of 2.4% of the seeds weight and had, as major constituents, beta-elemene (48.19%), trans-caryophyllene (19.51%), and epi-bicyclosesquiphellandrene (12.24%). The EOPPgfl sample showed mild acute toxicity and its calculated median lethal dose (LD50) was 3.38 g/kg. EOPPgfl (20-60 mg/kg) showed antinociceptive activity as evidenced by several tests and inhibited writhing induced by acetic acid. The maximum effect was obtained with the 30 mg/kg dose and at 60 min after its administration. EOPPgfl also decreased formalin-induced nociception, as verified by the inhibition of the first and second phase of the formalin test. At 30 mg/kg, EOPPgfl also decreased thermally stimulated nociception. Nociception may be related to inflammatory and antiedematogenic activity and at doses ranging 10-100 mg/kg, EOPPgfl blocked dextran- and carrageenan-induced edema. The results demonstrated that EOPPgfl presented, at doses approximately 100 times smaller than LD50, an antinociceptive effect that probably was due to anti-inflammatory activities.
Assuntos
Analgésicos/farmacologia , Fabaceae/química , Nociceptividade/efeitos dos fármacos , Óleos Voláteis/farmacologia , Extratos Vegetais/farmacologia , Óleos de Plantas/farmacologia , Animais , Anti-Inflamatórios/farmacologia , Camundongos , Medição da Dor , Distribuição Aleatória , Reprodutibilidade dos Testes , Sementes/química , Fatores de Tempo , Resultado do TratamentoRESUMO
Lippia sidoides Cham is a typical herb species of Northeast Brazil with widespread use in folk medicine. The major constituents of the essential oil of L. sidoides (EOLs) are thymol, p-cymene, myrcene, and caryophyllene. Several studies have shown that the EOLs and its constituents have pharmacological effects, including antibacterial, anti-inflammatory, antioxidant and neuroprotective activity. Therefore, this work aimed to investigate the effects of the EOLs and their main constituents on rat sciatic nerve excitability. The sciatic nerves of adult Wistar rats were dissected and mounted in a moist chamber. Nerves were stimulated by square wave pulses, with an amplitude of 40 V, duration of 100 µs to 0.2 Hz. Both EOLs and thymol inhibited compound action potential (CAP) in a concentration-dependent manner. Half maximal inhibitory concentration for CAP peak-to-peak amplitude blockade were 67.85 and 40 µg/mL for EOLs and thymol, respectively. CAP peak-to-peak amplitude was significantly reduced by concentrations ≥60 µg/mL for EOLs and ≥30 µg/mL for thymol. EOLs and thymol in the concentration of 60 µg/mL significantly increased chronaxie and rheobase. The conduction velocities of 1st and 2nd CAP components were also concentration-dependently reduced by EOLs and thymol in the range of 30-100 µg/mL. Differently from EOLs and thymol, p-cymene, myrcene and caryophyllene did not reduce CAP in the higher concentrations of 10 mM. These data demonstrated that EOLs and thymol inhibited neuronal excitability and were promising agents for the development of new drugs for therapeutic use.
Assuntos
Alcenos/farmacologia , Lippia/química , Monoterpenos/farmacologia , Óleos Voláteis/farmacologia , Nervo Isquiático/efeitos dos fármacos , Sesquiterpenos/farmacologia , Timol/farmacologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Monoterpenos Acíclicos , Animais , Cimenos , Feminino , Masculino , Bloqueio Nervoso/métodos , Condução Nervosa/efeitos dos fármacos , Óleos Voláteis/química , Sesquiterpenos Policíclicos , Ratos Wistar , Reprodutibilidade dos Testes , Nervo Isquiático/fisiologia , Fatores de TempoRESUMO
Lippia alba is empirically used for infusions, teas, macerates, and hydroalcoholic extracts because of its antispasmodic, analgesic, sedative, and anxiolytic effects. Citral is a mixture of trans-geranial and cis-neral and is the main constituent of L. alba essential oil and possesses analgesic, anxiolytic, anticonvulsant, and sedative effects. The present study evaluated the effects of the essential oil of L. alba (EOLa) and citral on compound action potentials (CAPs) in Wistar rat sciatic nerves. Both drugs inhibited CAP in a concentration-dependent manner. The calculated half-maximal inhibitory concentrations (IC50) of peak-to-peak amplitude were 53.2 µg/mL and 35.00 µg/mL (or 230 µM) for EOLa and citral, respectively. Peak-to-peak amplitude of the CAP was significantly reduced by 30 µg/mL EOLa and 10 µg/mL citral. EOLa and citral (at 60 and 30 µg/mL, values close to their respective IC50 for CAP blockade) significantly increased chronaxy and rheobase. The conduction velocity of the first and second CAP components was statistically reduced to â¼86% of control with 10 µg/mL EOLa and â¼90% of control with 3 µg/mL citral. This study showed that EOLa inhibited nerve excitability and this effect can be explained by the presence of citral in its composition. Both EOLa and citral showed inhibitory actions at lower concentrations compared with other essential oils and constituents with local anesthetic activity. In conclusion, these data demonstrate that EOLa and citral are promising agents in the development of new drugs with local anesthetic activity.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Lippia/química , Óleos Voláteis/farmacologia , Nervo Isquiático/efeitos dos fármacos , Animais , Feminino , Masculino , Ratos , Ratos Wistar , Fatores de TempoRESUMO
The aim was to evaluate the effect of different doses of two biostimulants on the productivity and canopy structure of Urochloa brizantha cv. Marandu grass in the establishment fase. The study was conducted in Universidade Federal Rural da Amazônia, Parauapebas, Pará, Brazil. One module of 35 plots of 25m² were established. A completely randomized experimental design was used, with seven treatments and five replicates. The treatments included a control, 0.5, 1, and 2kg/ha of biostimulant A (BIOST.A); and 0.25, 0.5, and 1L/ha of biostimulant B (BIOST.B). Three collections were performed. The data for application of the two biostimulants were analyzed separately, using the Dummy variable method and regression analysis. The application of 2kg/ha BIOST.A resulted in increases of 842kg/ha in the forage mass. The application of BIOST.B on Marandu grass resulted in a linear increase in stem mass. The application of 2kg/ha BIOST.A in the establishment of Marandu grass result in higher growth rates, forage accumulation, and stem proportion in the canopy.(AU)
Objetivou-se avaliar o efeito de diferentes doses de dois bioestimulantes sobre a produtividade e a estrutura do dossel do capim Urochloa brizantha cv. Marandu na fase de estabelecimento. O estudo foi realizado na Universidade Federal Rural da Amazônia, Parauapebas, Pará, Brasil. Um módulo de 35 parcelas de 25m² foi estabelecido. Utilizou-se delineamento experimental inteiramente ao acaso, composto de sete tratamentos e cinco repetições cada. Os tratamentos incluídos no controle foram: 0,5, 1 e 2kg/ha de bioestimulante A (BIOST.A); 0,25; 0,5 e 1L/ha de bioestimulante B (BIOST.B). Foram realizadas três coletas. Os dados para a aplicação dos dois bioestimulantes foram analisados separadamente, utilizando-se organização por método variável Dummy e análise de regressão. A aplicação de 2kg/ha BIOST.A resultou em incrementos de 842kg/ha na massa de forragem. A aplicação do BIOST.B na grama marandu resultou em aumento linear na produção de massa do caule. A aplicação de 2kg/ha BIOST.A no estabelecimento de erva de marandu resultou em maiores taxas de crescimento, acumulação de forragem e proporção de caule no dossel.(AU)
Assuntos
Ecossistema Amazônico , Fertilizantes , Poaceae/crescimento & desenvolvimento , Ácidos IndolacéticosRESUMO
The objective of this study was to evaluate the effect of the partial replacement of elephant grass silage with babassu (Orbignya speciosa) on the performance, intake, digestibility, and carcass weight gain of sheep. Fifty-four castrated male lambs (19.08±2.76kg) were distributed in a completely randomized design and administered one of the following treatments: 0.0, 12.5, 25.0, 37.5 or 50% dry matter (%DM) replacement of elephant grass silage with babassu cake. No difference (P> 0.05) was observed in the dry matter, crude protein, and neutral detergent fiber intake, but the ether extract intake increased (P< 0.05). The digestibility of the dry matter, neutral detergent fiber, and total digestible nutrients were unaffected. The crude protein digestibility decreased (P< 0.05), and the ether extract digestibility increased with the replacement of the elephant grass. There were no changes in mean daily weight gain and carcass weight gain. In the carcasses, a linear increase was observed in the proportion of the ether extract, and the crude protein decreased. The replacement of the silage with the babassu cake by up to 50% did not change the performance of sheep, however it led to an increase in fat deposit in the carcass.
Objetivou-se avaliar a substituição parcial da silagem de capim elefante por torta de babaçu (Orbignya speciosa) sobre o desempenho, consumo, digestibilidade, composição química e ganho em peso de carcaça de ovinos. Cinquenta e quatro machos, castrados (19,08±2,76kg) foram distribuídos em delineamento inteiramente casualizado e administrado um dos seguintes tratamentos: 0.0, 12.5, 25.0, 37.5 e 50% (%MS) de substituição da silagem pela torta de babaçu. Não houve diferença (P> 0.05) na ingestão de matéria seca, proteína bruta e fibra em detergente neutro, porém o consumo de extrato etéreo aumentou (P< 0.05). A digestibilidade da matéria seca, fibra em detergente neutro e nutrientes digestíveis totais não foram alterados, no entanto, os coeficientes de digestibilidade da proteína bruta reduziu (P< 0.05) e do extrato etéreo aumentou (P< 0.05), com a substituição. Não houve alterações no ganho de peso médio diário e ganho de peso em carcaça. Nas carcaças, observou-se aumento linear na proporção do extrato etéreo, no entanto a porcentagem de proteína bruta diminuiu. O aumento no extrato etéreo da carcaça mostrou uma tendência linear. A substituição da silagem pela torta de babaçu em até 50% não alterou o desempenho de ovinos, porém levou a aumento na deposição de gordura na carcaça.
Assuntos
Animais , Masculino , Carneiro Doméstico , Ração AnimalRESUMO
The transport of myo-inositol is the main mechanism for the maintenance of its high intracellular levels. We aimed to measure the mRNA and protein levels of myo-inositol cotransporters in the sciatic nerve (SN) and dorsal root ganglia (DRG) during experimental diabetes. Streptozotocin-induced (STZ; 4, 8, and 12 weeks; 65 mg/kg; ip) diabetic rats (DB) and age-matched euglycemic (E) rats were used for the analysis of mRNA and protein levels of sodium myo-inositol cotransporters 1, 2 (SMIT1, SMIT2) or H+/myo-inositol cotransporter (HMIT). There was a significant reduction in the mRNA levels for SMIT1 in the SN and DRG (by 36.9 and 31.0%) in the 4-week DB (DB4) group compared to the E group. SMIT2 was not expressed in SN. The mRNA level for SMIT2 was up-regulated only in the DRG in the DB4 group. On the other hand, the protein level of SMIT1 decreased by 42.5, 41.3, and 44.8% in the SN after 4, 8, and 12 weeks of diabetes, respectively. In addition, there was a decrease of 64.3 and 58.0% of HMIT in membrane and cytosolic fractions, respectively, in the SN of the DB4 group. In the DRG, there was an increase of 230 and 86.3% for SMIT1 and HMIT, respectively, in the DB12 group. The levels of the main inositol transporters, SMIT1 and HMIT, were greatly reduced in the SN but not in the DRG. SMIT-1 was selectively reduced in the sciatic nerve during experimental STZ-induced diabetes.
Assuntos
Animais , Masculino , Ratos , Nervo Isquiático/metabolismo , Transporte Biológico Ativo/fisiologia , RNA Mensageiro/metabolismo , Diabetes Mellitus Experimental/metabolismo , Gânglios Espinais/metabolismo , Inositol/metabolismo , Regulação para Cima , Western Blotting , Estreptozocina , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Estragole is a volatile terpenoid, which occurs naturally as a constituent of the essential oils of many plants. It has several pharmacological and biological activities. The objective of the present study was to investigate the mechanism of action of estragole on neuronal excitability. Intact and dissociated dorsal root ganglion neurons of rats were used to record action potential and Na+ currents with intracellular and patch-clamp techniques, respectively. Estragole blocked the generation of action potentials in cells with or without inflexions on their descendant (repolarization) phase (Ninf and N0 neurons, respectively) in a concentration-dependent manner. The resting potentials and input resistances of Ninf and N0 cells were not altered by estragole (2, 4, and 6 mM). Estragole also inhibited total Na+ current and tetrodotoxin-resistant Na+ current in a concentration-dependent manner (IC50 of 3.2 and 3.6 mM, respectively). Kinetic analysis of Na+ current in the presence of 4 mM estragole showed a statistically significant reduction of fast and slow inactivation time constants, indicating an acceleration of the inactivation process. These data demonstrate that estragole blocks neuronal excitability by direct inhibition of Na+ channel conductance activation. This action of estragole is likely to be relevant to the understanding of the mechanisms of several pharmacological effects of this substance.
RESUMO
Essential oils (EO) are volatile liquids responsible for the aroma of plants. Pterodon polygalaeflorus seeds have received widespread use in folk medicine for the treatment of inflammatory diseases. For this reason and because Pterodon polygalaeflorus seeds have great EO content, which is frequently pharmacologically active, the present study aimed to evaluate the antinociceptive effect of EO from Pterodon polygalaeflorus (EOPPgfl) and its acute toxic effects. The EEOPPgfl sample, which was extracted by steam distillation of the seeds, had a yield of 2.4% of the seeds weight and had, as major constituents, beta-elemene (48.19%), trans-caryophyllene (19.51%), and epi-bicyclosesquiphellandrene (12.24%). The EOPPgfl sample showed mild acute toxicity and its calculated median lethal dose (LD50) was 3.38 g/kg. EOPPgfl (20-60 mg/kg) showed antinociceptive activity as evidenced by several tests and inhibited writhing induced by acetic acid. The maximum effect was obtained with the 30 mg/kg dose and at 60 min after its administration. EOPPgfl also decreased formalin-induced nociception, as verified by the inhibition of the first and second phase of the formalin test. At 30 mg/kg, EOPPgfl also decreased thermally stimulated nociception. Nociception may be related to inflammatory and antiedematogenic activity and at doses ranging 10-100 mg/kg, EOPPgfl blocked dextran- and carrageenan-induced edema. The results demonstrated that EOPPgfl presented, at doses approximately 100 times smaller than LD50, an antinociceptive effect that probably was due to anti-inflammatory activities.
Assuntos
Animais , Coelhos , Óleos de Plantas/farmacologia , Óleos Voláteis/farmacologia , Extratos Vegetais/farmacologia , Nociceptividade/efeitos dos fármacos , Analgésicos/farmacologia , Fabaceae/química , Sementes/química , Fatores de Tempo , Medição da Dor , Distribuição Aleatória , Reprodutibilidade dos Testes , Resultado do Tratamento , Anti-Inflamatórios/farmacologiaRESUMO
Various essential oils are rich in carvacrol, a monoterpenic phenol isomeric with thymol. This study was undertaken to assess the vasorelaxant effects of thymol and carvacrol in rat isolated aorta and the putative mechanisms underlying these effects. Thymol and carvacrol produced a concentration-dependent relaxation on the aortic ring preparations pre-contracted using KCl (IC(50) value of 64.40 +/- 4.41 and 78.80 +/- 11.91 microm, respectively) or using phenylephrine (PHE, 0.1 microm) (IC(50) value of 106.40 +/- 11.37 and 145.40 +/- 6.07 microm, respectively) and inhibited the concentration-response curves of aortic rings to PHE or KCl. In Ca(2+)-free medium with ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (2 mm), thymol and carvacrol both at 1000 microm completely abolished the phasic component of PHE-induced endothelium-containing ring contractions. At 400 microm, thymol and carvacrol significantly reduced the CaCl(2)-induced contractions in Ca(2+)-free medium. Furthermore, both thymol and carvacrol (300 and 1000 microm) significantly reduced the contraction evoked by phorbol dibutyrate (1 microm), an activator of protein kinase C. Magnitude of this inhibitory effect was enhanced in the presence of the Ca2+ pump inhibitor, thapsigargin (1 microm). At 1000 microm, neither thymol nor carvacrol altered the resting potential of vascular smooth muscle cells. In conclusion, thymol and carvacrol induced an endothelium-independent relaxation in rat isolated aorta, an effect that seems mediated through some mechanisms probably involving a transduction pathway between Ca(2+) release from sarcoplasmic reticulum and/or regulation of the Ca2+ sensitivity of the contractile system. Moreover, it's conceivable that thymol and carvacrol, at low concentrations, block the Ca(2+) influx through the membrane.
Assuntos
Aorta Torácica/efeitos dos fármacos , Monoterpenos/farmacologia , Músculo Liso Vascular/efeitos dos fármacos , Timol/farmacologia , Vasodilatação/efeitos dos fármacos , Vasodilatadores/farmacologia , Animais , Aorta Torácica/fisiologia , Cimenos , Esquema de Medicação , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/fisiologia , Masculino , Monoterpenos/química , Músculo Liso Vascular/fisiologia , Técnicas de Cultura de Órgãos , Fenóis/química , Fenóis/farmacologia , Ratos , Ratos Wistar , Estereoisomerismo , Timol/química , Vasodilatação/fisiologia , Vasodilatadores/químicaRESUMO
Estragole is a volatile terpenoid, which occurs naturally as a constituent of the essential oils of many plants. It has several pharmacological and biological activities. The objective of the present study was to investigate the mechanism of action of estragole on neuronal excitability. Intact and dissociated dorsal root ganglion neurons of rats were used to record action potential and Na+ currents with intracellular and patch-clamp techniques, respectively. Estragole blocked the generation of action potentials in cells with or without inflexions on their descendant (repolarization) phase (Ninf and N0 neurons, respectively) in a concentration-dependent manner. The resting potentials and input resistances of Ninf and N0 cells were not altered by estragole (2, 4, and 6 mM). Estragole also inhibited total Na+ current and tetrodotoxin-resistant Na+ current in a concentration-dependent manner (IC50 of 3.2 and 3.6 mM, respectively). Kinetic analysis of Na+ current in the presence of 4 mM estragole showed a statistically significant reduction of fast and slow inactivation time constants, indicating an acceleration of the inactivation process. These data demonstrate that estragole blocks neuronal excitability by direct inhibition of Na+ channel conductance activation. This action of estragole is likely to be relevant to the understanding of the mechanisms of several pharmacological effects of this substance.