ANTHO-RFAMIDE IMMUNOREACTIVITY IN NEURONAL SYNAPTIC AND NONSYNAPTIC VESICLES OF SEA-ANEMONES

Antho-RFamide is a neuropeptide isolated from the sea anemone Anthople ura elegantissima. Antho-RFamide immunoreactivity was localized in fou r different populations of neuronal vesicles in the tentacle nerve ple xus of Anthopleura. Small, opaque, neuronal vesicles, averaging 49 nm in diameter, were gold-labeled at two-way synapses. Heterogranular ves icles, averaging 184 nm in diameter, were gold-labeled in a neuronal s welling adjacent to a muscle cell process. These vesicles were similar in size to a third class of gold-labeled dense-cored vesicles. A four th class of immunogold-labeled vesicles observed in neuronal swellings had light cores and averaged 129 nm in diameter. Using 5-nm gold part icles, we observed a heavy labeling of the granular cores of the dense -cored vesicles, suggesting that the immunoreactivity is specific to t he vesicle core. The ultrastructural demonstration of Antho-RFamide im munoreactivity in interneuronal synaptic vesicles, together with the i mmunofluorescence and electrophysiological studies of other investigat ors, suggest that Antho-RFamide plays a role in neurotransmission in s ea anemones.