Sensory and neurosecretory innervation of leech nephridia is accomplished by a single neurone containing FMRFamide.

The neural control of the excretory system of the medicinal leech Hirudo medicinalis has been characterized morphologically and chemically using light and electron microscopy, immunocytochemistry and biochemistry. Immunoreactivity against RFamide-like peptides revealed elaborate neuronal aborizations of a neurone in the nephridium, around the urinary bladder sphincter and in the central nervous system. The processes arose from the nephridial nerve cell (NNC), a previously identified receptor neurone. Using a combination of reverse-phase high pressure liquid chromatography, radioimmunoassay and subsequent Edman degradation and mass spectrometry, authentic FMRFamide has been identified as the major peptide of the NNC. Sensory and neurosecretory innervation of the nephridia is thus accomplished by a single neurone, which is thought to modulate nephridial performance.