An arginine vasotocin-like neuropeptide is present in the nervous system of the marine mollusc Aplysia californica.

Radioimmunoassays and high pressure liquid chromatography have been used to demonstrate the presence of an arginine-vasotocin-like peptide (AVT) in the anterior ganglia of Aplysia. Previously, AVT, using similar methods, was found to be present only in vertebrates. AVT when perfused over the abdominal ganglion (10(-6)-10(-12)M) was found to increase the bursting activity of R15, to decrease the bursting activity of L3-L6 and to increase the CNS's suppressive influence over the gill withdrawal reflex evoked by siphon stimulation. The AVT present in the nervous system of Aplysia may mediate long-term suppression of gill reflex behaviors induced by factors such as satiation and, as well, regulate the activity of certain neurosecretory neurons.