THE FMRFamide-LIKE NEUROPEPTIDE OF APLYSIA IS FMRFamide

Area of Science:

• Neuroscience
• Marine Biology
• Biochemistry

Background:

• Molluscan neuropeptides FMRFamide and SCP_B are known signaling molecules.
• Previous studies suggested a potential structural relationship between FMRFamide and SCP_B.

Purpose of the Study:

• To identify and characterize the FMRFamide-like peptide in Aplysia.
• To determine if the FMRFamide-like peptide is indeed FMRFamide or SCP_B.
• To elucidate the physiological roles of these neuropeptides in Aplysia.

Main Methods:

• Extraction and purification of head ganglia from Aplysia brasiliana.
• Gel filtration and cation exchange chromatography.
• Radioimmunoassays (RIA) for FMRFamide and SCP_B.
• Amino acid composition analysis and carboxypeptidase Y digestion.
• Functional assays on the radula protractor muscle and isolated heart.

Main Results:

• Immunoreactive FMRFamide, but not SCP_B, coeluted with authentic FMRFamide.
• Purified FMRFamide exhibited identical chromatographic behavior, amino acid composition, and RIA binding to synthetic FMRFamide.
• Purified and synthetic FMRFamide showed identical dose-response effects on the radula protractor muscle.
• FMRFamide was concentrated in pedal and pleural ganglia, while SCP_B was found in the buccal ganglion.
• Synthetic SCP_B had no significant effect on the tested muscle or heart preparations.

Conclusions:

• The FMRFamide-like peptide in Aplysia is confirmed to be FMRFamide.
• FMRFamide has now been identified in two distinct molluscan classes.
• The proposed structural relationship between FMRFamide and SCP_B is coincidental.
• FMRFamide and SCP_B likely possess different physiological functions in Aplysia.