cocaine

To investigate, his team injected cocaine, capsaicin or both at once into the abdomens of several groups of about 30 mice.

他的团队将辣椒素或可卡因中的一种，或同时将两种注射进几组老鼠的腹部，每组约30只。

Then the researchers repeated the experiment, but this time they injected rats with a dose of cocaine or morphine on one side and with a neutral saline solution on the other.

然后，研究人员重复这项实验，但是这次他们给一边的小白鼠注射小剂量的可卡因或吗啡，而另一边注射中性盐水。