Ischemia Increases the Twitch Latent Period in the Soleus and Extensor Carpi Radialis Longus Muscles from Adult Rats

Complete ischemia and reperfusion effects on twitch force ((F<bold>t</bold>)), twitch latent period (TLP), maximal rate of rise of twitch tension (F/t)(max), and twitch maximum relaxation rate (TMRR) were assessed. We divided 36 adult rats into four groups; two control groups (n = 9), a group undergoing 1hour of ischemia followed by 1hour of reperfusion (n = 9), and one group exposed to 2hours of ischemia followed by 1hour of reperfusion (n = 9). We have induced twitch contractions every 10minutes in the soleus and the extensor carpi radialis longus (ECRL). Twitch contractions were recorded and then analyzed for (F<bold>t</bold>), TLP, (F/t)(max), and TMRR. During 1hour and 40minutes of ischemia, TLP increased to 179 +/- 24% (p < 0.05) in the soleus and to 184 +/- 16% (p < 0.05) in the ECRL, an effect that was partially recovered during 1hour of reperfusion. This increase started after 20minutes of ischemia in the soleus and after 40minutes of ischemia in the ECRL. The increase was faster in the ECRL and peaked at the same time for both muscular groups. (F<bold>t</bold>) and (F/t)(max) decreased during 1hour of ischemia to 46 +/- 7% (p < 0.05) in the soleus and to 40 +/- 7% (p < 0.05) in the ECRL. TMRR decreased during 1hour of ischemia to 39 +/- 5% (p < 0.05) in the soleus and to 54 +/- 8% (p < 0.05) in the ECRL. During 1hour of reperfusion all of them recovered close to control values.