During the summer, we are joined by two undergraduates as well as several visiting faculty from other institutions. All of our work involves the horseshoe crab, an organism I met as a graduate student at Purdue. In my thesis work I showed that the inhibitory neurotransmitter that regulated the heart beat was serotonin, a widely distributed derivative of the amino acid tryptophan. The horseshoe crab has a simple nervous system, with hardy cells. The organism and the cells are physiologically durable.
Isolated cells continue to work for hours without any apparent defect.
In contrast, mammalian cells are much more fragile and begin to show physiological defects after 30 minutes. The horseshoe crab is most famous in neuroscience largely because of Hartline's work on its visual system. I began to worry about other questions, however, particularly about the ways in which particular nerve cells come to use acetylcholine as a neurotransmitter rather than, say, GABA or serotonin. Every summer I go to the Marine Biological Laboratory at Woods Hole, Massachusetts, where horseshoe crabs are plentiful. The rest of the year, live animals are shipped to me in Nashville.