ABSTRACT
Abstract Objective: To analyze and compare the effect of temperature on the average velocity of the linear phase and the exponential phase stages produced by periodic stimulation with simple twitching or with tetanus in the toad sartorius. Methods: an in vitro experimental study with a sample of 46 toad sartorius muscles randomly selected. At the temperatures studied, peak tension produced with two stimulus patterns (twitching and tetanus) were measured until reaching the corresponding muscle fatigue in each case. The tension velocity drop in the linear phase and the exponential phase for each type of fatigue were calculated, and the regression slopes obtained with the Arrhenius equation were compared. Results: The temperatures used (1 to 12°C) significantly affected the velocity of fatigue in the stages of linear and exponential phases of both types of fatigue (p <0.05). The function of which the fatigue curves were adjusted to the temperatures used was similar to the function used with the curves at room temperature. When comparing the slopes of Arrhenius regression in the exponential phase and the different stages of the linear phase of each fatigue and between both fatigues, no significant differences were found (p>0.05). Conclusions: The temperature significantly affected average development velocity of fatigue in the different phases of the two types of fatigue, but when comparing slopes of most regressions corresponding to Arrhenius there were no significant differences, suggesting that the mechanisms underlying the different stages of fatigue have equal sensitivity to temperature.
Resumen Objetivos: Analizar y comparar el efecto de la temperatura en la velocidad promedio de las etapas de la fase lineal y de la fase exponencial de la fatiga producida por estimulación periódica con sacudida simple o con tétanos en el sartorio de sapo. Métodos: Estudio experimental, in vitro; muestra: 46 músculos de sartorio de sapo seleccionados aleatoriamente. A las temperaturas estudiadas, se midió la tensión pico producida con dos patrones de estímulo (sacudida simple o tétanos) hasta llegar en cada caso a un tipo de fatiga muscular, se calculó la velocidad de caída de la tensión en las etapas de la fase lineal y en la fase exponencial de cada tipo de fatiga y se compararon las pendientes de las regresiones obtenidas con la ecuación de Arrhenius. Resultados: Las temperaturas utilizadas (1 a 12°C) afectaron significativamente (p<0,05) la velocidad de la fatiga en las etapas de las fases lineal y exponencial de ambos tipos de fatiga. La función con que se ajustaron las curvas de fatiga a las temperaturas usadas fue similar a la usada con las curvas a temperatura ambiente. Al comparar entre las pendientes de las regresiones de Arrhenius de la fase exponencial y las diferentes etapas de la fase lineal de cada una de las fatigas y entre ambas fatigas, no hubo diferencias significativas (p>0,05). Conclusiones: La temperatura afectó significativamente la velocidad promedio de desarrollo de la fatiga en las diferentes fases de los dos tipos de fatiga, pero al comparar las pendientes de la mayoría de las regresiones correspondientes de Arrhenius, no se encontraron diferencias significativas, lo cual sugiere que, los mecanismos que subyacen a las diferentes etapas de la fatiga tienen igual sensibilidad a la temperatura.
ABSTRACT
The compound 6o (at 0.5, 1 and 2 mg/kg, ip) with optimum log P and pA2 value, was subjected to forced swim test (FST) and tail suspension test (TST). The compound 6o significantly reduced the duration of immobility in mice without affecting the base line locomotion in actophotometer. Moreover, 6o (2 mg/kg, ip), potentiated the 5-hydroxytryptophan (5-HTP)-induced head twitch responses in mice and at 1 and 2 mg/kg, ip antagonized the reserpine-induced hypothermia (RIH) in rats. In interaction studies with various standard drugs/ligands using FST, 6o (1 and 2 mg/kg, ip) potentiated the anti-depressant effect fluoxetine (5 mg/kg, ip) and reversed the depressant effect of parthenolide (1 mg/kg, ip) by reducing the duration of immobility. Furthermore, 6o (1 and 2 mg/kg, ip) potentiated the effect of bupropion (10 mg/kg, ip) in TST. The behavioural anomalies of the olfactory bulbectomised (OBX) rats were augmented by chronic 6o (1 and 2 mg/kg) treatment as observed from the modified open field test (parameters: ambulation, rearing, fecal pellet). The results suggest that compound 6o exhibited anti-depressant like effect in rodent models of depression.