FMRFamide (H-Phe-Met-Arg-Phe-NH2) is a
neuropeptide from a broad family of FMRFamide-related peptides (FaRPs) all sharing an -RFamide sequence at their
C-terminus
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When the protein is ...
. First identified in
Hard clam (''Mercenaria mercenaria''),
it is thought to play an important role in cardiac activity regulation. Several FMRFamide related peptides are known, regulating various cellular functions and possessing pharmacological actions, such as anti-opiate effects. In ''Mercenaria mercenaria'', FMRFamide has been isolated and demonstrated to increase both the force and frequency of the heartbeat through a biochemical pathway that is thought to involve the increase of cytoplasmic
cAMP in the ventricular region.
FMRFamide is an important neuropeptide in several phyla such as
Insecta,
Nematoda,
Mollusca
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
, and
Annelida.
It is the most abundant neuropeptide in
endocrine
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
cells of insect alimentary tracts along with
allatostatin and
tachykinin
Tachykinin peptides are one of the largest families of neuropeptides, found from amphibians to mammals. They were so named due to their ability to rapidly induce contraction of gut tissue. The tachykinin family is characterized by a common C-termi ...
families, however the neuropeptide’s function is not known. Generally, the neuropeptide is encoded by several genes such as flp-1 through flp-22 in
C. elegans
''Caenorhabditis elegans'' () is a free-living transparent nematode about 1 mm in length that lives in temperate soil environments. It is the type species of its genus. The name is a blend of the Greek ''caeno-'' (recent), ''rhabditis'' ( ...
. The common precursor of the FaRPs is modified to yield many different neuropeptides all having the same FMRFamide sequence. Moreover, these peptides are not functionally redundant.
In invertebrates, the FMRFamide-related peptides are known to affect
heart rate,
blood pressure
Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...
,
gut motility,
feeding behaviour and
reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual or ...
. In vertebrates such as mice, they are known to affect
opioid receptors resulting in elicitation of naloxone-sensitive antinociception and reduction of
morphine-induced antinociception.
Detection of this neuropeptide is important because its expression lays down the foundation of the CNS in the early stages of development in invertebrates. In recent years, neuromodulatory actions of FMRFamide in invertebrates have become more apparent. This is, in part, due to the extensive studies done on the Planorbid and Lymnaeid families of pond snails.
See also
*
Neuropeptide VF precursor
References
External links
FMRFamide antibody (ab10352) datasheet
{{Neuropeptides
Biomolecules
Neurotransmitters