Daphnia magna may be a useful invertebrate preparation for understanding cardiac function. This study was an examination of the effects of mibefradil, a blocker of the T-type calcium ion channel, on the Daphnia heart. T-type calcium ion channels are known to underlie pacemaker function in the vertebrate heart. Therefore, this study helps to establish similarities between the Daphnia heart and vertebrate heart. Daphnia were pinned to a Sylgard-lined petri dish and the animal’s heart was visualized with a Nikon Eclipse Ti inverted microscope. Pinned Daphnia were allowed five minutes to adjust to their environment before recording heart rate. Immediately after this “adjustment” period, the heartbeat was recorded using video microscopy to provide a baseline heart rate for comparison. Daphnia were then exposed to mibefradil, and heart rates were recorded at five minutes and again at ten minutes after the application of mibefradil to observe the effect of this drug on heart rate. Mibefradil decreased the heart rate as predicted.

The Effects of Mibefradil, a T-type Calcium Ion Channel Blocker, on Daphnia magna Heartbeat