RESUMO
In vivo effects of a single dose of norepinephrine (NE) and epinephrine (EP) were studied on the rate of tissue (liver and skeletal muscle) respiration in Rana limnocharis (hibernating Sp.) and Rana cyanophlyctis (non-hibernating Sp.) during winter and summer months after 10 and 30 min, 1, 6, 12 and 24 hr of administration. During winter both NE and EP induced significant increase in the rate of tissues respiration only after 30 min after their administration in both the species and the stimulatory effect lasted up to 6 hr. During summer, however, NE and EP stimulated respiratory rate of tissues comparatively after a shorter lag period (10 to 30 min) in R. limnocharis than that of R. cyanophlyctis (30 min to 6 hr). These findings seem to suggest that NE and EP can stimulate tissue respiration very quickly, and, therefore, might be suitable as emergency hormones for instant/faster stimulation of energy metabolism in amphibians.