Changes in the Lactate Threshold During Treadmill Exercise After Microsphere-Induced Infarction in Rats

Abstract

Objectives The aim of this study was to clarify changes in the lactate threshold (LT) in the acute period after cerebral infarction.Methods Cerebral infarction was induced by the injection of microspheres (MS) into the right internal carotid artery. To estimate the degree of neurological deficit caused by surgery, the behaviors of all rats were evaluated in terms of typical symptoms of stroke in rats. A rotarod test was used to evaluate equilibrium function. Rats were forced to perform stepwise treadmill exercises and serial changes in the blood lactate concentration were measured for determination of the LT. ResultsThe average treadmill speed at the LT and rotarod performance in MS rats was significantly lower than those in sham-operated rats on the 2 nd days after surgery.However, while neurological deficits disappeared on the 7 th days after surgery in MS rats, the LT and rotarod performance were significantly lower than those in shamoperated rats. ConclusionThese results suggest that the decrease in the LT in the acute period following cerebral infarction may be induced by impairment of the equilibrium function.Other possibilities are also discussed.

Evaluation of the Lactate Threshold of Rats Using External Jugular Vein Catheterization

“…The results obtained by Takahashi et al 6) were higher than those we report in the present study. The results of Takahashi et al 6) were obtained by drawing blood from the tail vein during the rest period, not while the rat was running. Using our method, it was possible to frequently and reliably measure blood lactate concentrations during the incremental exercise tests for all the rats.…”

“…Takahashi et al 6) found the running speed of rats at the lactate threshold was 20 m/min, and the blood lactate concentration at the lactate threshold was 1.4 mmol/L. The results obtained by Takahashi et al 6) were higher than those we report in the present study.…”

“…Blood lactate concentrations were measured using a portable lactate analyzer (Lactate Pro; Arkray, Japan). The lactate analyzer software (MEQNET LT Manager; Arkray, Japan) determined the 2-line combination that minimizes the total sum of squares for fitting all data 6) . To determine the lactate threshold, a graph was made from the results of the blood lactate concentrations at the different running speeds.…”

“…There are some reports showing that maximal oxygen uptake 3,4) and lactate threshold [5][6][7][8] can be used to determine the exercise capacity of rats. However, measurement of maximal oxygen uptake needs special equipment, and it is not possible to measure the ventilation response and anaerobic threshold during treadmill running when using a mixing chamber.…”

“…Use of the tail vein for blood sampling 5,6) cannot be used when performing incremental exercise tests, because the tail must be stabilized to draw blood, which prevents the rat from running. It is possible to take blood lactate concentrations frequently when using an external jugular vein catheterization.…”