FMRF-amide-like substances in the leech. I. Immunocytochemical localization

Area of Science:

• Neuroscience
• Immunocytochemistry
• Leech Physiology

Background:

• FMRF-amide is a neuropeptide found in various invertebrates.
• Its presence and function in the medicinal leech (Hirudo medicinalis) are not fully elucidated.
• Understanding neurochemical signaling is crucial for invertebrate neurobiology.

Purpose of the Study:

• To localize and identify neurons expressing FMRF-amide-like immunoreactivity (FLI) in the medicinal leech.
• To determine the distribution and potential roles of FMRF-amide-like substances in the leech nervous system.

Main Methods:

• Immunocytochemical techniques were employed to visualize FLI in leech ganglia.
• Synthetic FMRF-amide was used to preabsorb antisera, confirming antibody specificity.
• Lucifer Yellow cellular injection combined with indirect immunofluorescence identified specific neurons with FLI.

Main Results:

• Approximately 50 neurons per segmental ganglion exhibited FLI, with some showing restricted distribution.
• FLI was also detected in head and tail ganglia, nerve processes, and varicosities.
• Identified FLI-containing neurons included motor neurons (HE, RPE, LPE, AE, L), the HA modulatory neuron, interneuron 204, and AP cells.

Conclusions:

• FMRF-amide-like substances are widely distributed in the medicinal leech nervous system.
• FLI is present in various neuron types, including motor and modulatory neurons.
• These findings strongly suggest a role for FMRF-amide-like substances as significant neurochemical signals in leeches.