Quantitative analysis of the effects of different stimuli on the contraction of gastrocnemius in vivo and in vitro specimen

OBJECTIVE To quantitatively analyze the effects of direct and indirect stimuli on the contraction of gastrocnemius in vivo and in vitro specimen by self-programming. METHODS All specimens were divided into four groups: indirect stimuli on specimen in vivo group (n=12), direct stimuli on specimen in vivo group (n=8), indirect stimuli on specimen in vitro group (n=12), direct stimuli on specimen in vitro group (n=8). Indirect stimuli (via sciatic nerve) and direct stimuli (acupuncture needle piercing into gastrocnemius) (stimuli starting from 0 V, cycle 3 s, increment 0.02 V, 150 times) were acted on in vivo and in vitro sciatic nerve gastrocnemius muscle specimen respectively. The effects of electric intensity on the contraction of gastrocnemius were recorded by the experimental system of BL-420F. The data were processed and analyzed by the help of self-programming, to quantitatively obtain key parameters for a single contraction. RESULTS ① For in vivo specimen, compared with direct stimuli, effects of indirect stimuli were as follows: the threshold intensity, half-intensity and maximal intensity of the specimen were smaller (P＜0.05); the amplitude was larger, the contraction period was longer, and the rising slope was smaller (P＜0.05). ②For in vitro specimen, compared with direct stimuli, effects of indirect stimuli were as follows: the threshold intensity, half-intensity and maximal intensity of indirect stimuli were smaller (P＜0.05); the amplitude was larger, the contraction period was longer, and the rising slope was smaller (P＜0.05). ③Compared with in vitro specimen, there was no significant difference among all the above parameters of in vivo specimen, with either direct or indirect stimuli (P＞0.05). CONCLUSION There is no significant difference in the features of single contraction between in vivo and in vitro specimen with either direct or indirect stimuli. However, indirect stimuli can trigger gastrocnemius to produce single contraction more easily than direct stimuli, and the amplitude is larger than that of direct stimuli.