Caffeine inhibits serotonin's enhancement of EJP amplitude in crayfish deep extensor muscle

Abstract

Caffeine is commonly considered a psychoactive drug due to its stimulant properties present both in the behavioral increase in attention and at synapses throughout the body. At the neuromuscular junction, caffeine likely achieves its psychomotor stimulation by increasing EJP amplitude. However, research in the past year found that caffeine has a paradoxical effect at the flexor muscle: it inhibits serotonin-induced synaptic enhancement. We tested whether this behavior also occurs at the superficial extensor muscle. As previously observed at the flexor muscle, recorded EJP amplitudes in the crayfish extensor muscle returned to control levels once caffeine was introduced to a serotonin-rich saline solution.