“We might think of the curare as a ‘bubble’ that prevents acetylcholine from triggering an impulse. Fortunately, curare does not last long. The paralysis will wear off after an hour or two. That made curare useful in surgery.

It was used as a muscle relaxant for decades before synthetic alternatives became available. Of course, people had to receive assistance with breathing while the drug was in their system. But it was a blessing to surgeons and patients, in spite of the deadly potential of curare.

“Now we will turn to another drug to see a slightly different influence on neural computation: heroin.