L-glutamic acid, a possible neurotransmitter to anterior aorta of Aplysia

The effect of L-glutamate on muscle fibers of the anterior aorta of the marine gastropod Aplysia are characterized. Iontophoretically applied L-glutamate depolarized anterior aorta muscle fibers in 14% of the applications; no response was detected in the other applications. Responses to iontophoretically applied L-glutamate desensitize rapidly and are antagonized by 2-amino-4-phosphonobutyric acid (2-APB). 2-APB also blocked excitatory junctional potentials (EJPs) in the anterior aorta. No significant response to D-glutamate was observed. These characteristics match those of L-glutamate at the arthropod neuromuscular junction. Bath-applied L-glutamate also depolarizes anterior aorta muscle fibers, by a mechanism clearly different from that of iontophoretically applied L-glutamate. Present results make L-glutamate a candidate neurotransmitter to molluscan circulatory muscles.