Estrogen supplementation in the posthypoxic myoclonus rat model

The objective of the study was to investigate the effects of estrogen on se verity and duration of myoclonus in the rat cardiac arrest model of posthyp oxic myoclonus. Female sex hormones affect a variety of movement disorders and alter dopaminergic and serotonergic pharmacology. Although women repres ented three-fourths of patients from the original report of Lance and Adams and 80% of the largest published series, the impact of estrogens on myoclo nus has never been studied. Twelve previously ovariectomized female rats un derwent 8 minutes of mechanically induced cardiac arrest and were resuscita ted according to a standardized protocol. On the same day, they were random ly assigned to subcutaneous treatment with a 21-day, 0.5-mg, 17 beta -estra diol or matching placebo pellet. Animals were tested daily with 7 sets of 4 5 auditory stimuli for 10 days, and myoclonus scores were obtained using a 5-point interval scale. Comparisons were based on two-sample Wilcoxon rank- sum tests. Estrogen treatment significantly enhanced myoclonus intensity an d duration: mean peak myoclonus score, 210.2 +/- 18.0 versus 180 +/- 28.5 ( p = 0.031); mean number of days above baseline, 9.2 +/- 0.4 versus 5.7 +/- 2.3 (p = 0.004); mean score on day 10, 90.7 +/- 38.7 versus 27.0 +/- 20.6 ( p = 0.016). All estrogen-treated animals were above baseline on day 10 comp ared with none in the placebo group. Estrogen enhances and prolongs posthyp oxic myoclonus, suggesting that female gender and estrogen status may play a pivotal role as a risk factor for human posthypoxic myoclonus.