FMRFamide is endogenous to the Aplysia heart

Area of Science:

• Neuroscience
• Marine Biology
• Cardiovascular Physiology

Background:

• The neuropeptide FMRFamide is known to influence various physiological processes in mollusks.
• Its specific role and localization within the Aplysia californica heart require further investigation.

Purpose of the Study:

• To investigate the presence and localization of the molluscan neuropeptide FMRFamide in the heart of Aplysia californica.
• To explore the potential role of FMRFamide in regulating cardiac function in this marine invertebrate.

Main Methods:

• Immunohistochemical localization was employed to visualize FMRFamide-immunoreactive (FMRFamide-IR) structures within the Aplysia heart.
• High-performance liquid chromatography (HPLC) coupled with radioimmunoassays was used to identify and quantify FMRFamide and FLRFamide.
• Quantitative analysis compared the density of FMRFamide-IR varicosities in different heart regions (atrium, AV valve, ventricle).

Main Results:

• FMRFamide-immunoreactive (FMRFamide-IR) nerve fibers, varicosities, and neuronal somata were detected throughout the Aplysia heart.
• Significantly higher densities of FMRFamide-IR varicosities were found in the atrium and atrioventricular (AV) valve compared to the ventricle.
• The atrium showed a high density of FMRFamide-IR varicosities but lacked sensitivity to FMRFamide, suggesting a potential neurohemal function.

Conclusions:

• The study confirms the presence of FMRFamide and FLRFamide in the Aplysia heart, with distinct regional distribution.
• The atrium may function as a neurohemal organ for FMRFamide release, independent of central nervous system control.
• The presence of FMRFamide-IR somata suggests peripheral neurons contribute to modulating heart activity in Aplysia.