Native opioid-like peptides in Squilla mantis ganglia

Area of Science:

• Neurobiology
• Marine Biology
• Biochemistry

Background:

• Squilla mantis, an arthropod, exhibits sensitivity to opiates.
• Mammalian enkephalins are endogenous opioid peptides involved in pain modulation and reward pathways.

Purpose of the Study:

• To investigate the presence of mammalian-like enkephalin precursors in the suboesophageal ganglia of Squilla mantis.
• To characterize the opioid-like activity in Squilla mantis extracts.

Main Methods:

• Protein acid extracts were fractionated using gel filtration.
• Opioid-like activity was assessed using radioligand displacement assays and bioassays (guinea-pig ileum twitch response).
• High-performance liquid chromatography (HPLC) and immunoreactivity tests were employed for further characterization.

Main Results:

• Opioid-like activity was detected in a low molecular weight fraction (pool C).
• Proteolysis of higher molecular weight fractions (pools A and B) revealed activity in pool B, which inhibited electrically stimulated guinea-pig ileum.
• HPLC analysis of proteolyzed pool B showed activity distinct from known opioid peptide standards, and no immunoreactivity with anti-Met-enkephalin antibodies was observed.

Conclusions:

• Native opioid-like peptides are present in Squilla mantis.
• These peptides are likely derived from higher molecular weight precursors.
• The identified opioid-like peptides may differ structurally from mammalian enkephalins.