The stomatogastric nervous system of the medicinal leech: its anatomy, physiology and associated aminergic neurons

Blood feeding is an essential and signature activity of the medicinal leech species Hirudo verbana. Despite keen interest in understanding the neuronal substrates of this behavior, a major component of the nervous system associated with feeding has remained overlooked. In this study, for the first time, we report on the presence and characteristics of five stomatogastric ganglia (STGs) comprising the visceral stomatogastric nervous system (STN) of the leech. Although a brief report was published by Ruth Hanke in 1948 indicating that a ring of three ganglia (not five) was associated with the cephalic ganglia, this information was never integrated into subsequent neurobiological studies of feeding. Here, the anatomical features of the STGs are described, as are the morphological and electrophysiological characteristics of neurons originating in them. We also determined that two of the five STGs (STG-1 and STG-3) each contained two relatively large (ca. 40 µm diameter) serotonergic neurons. The STN was also enriched with dopaminergic and serotonergic arborizations; however, no intrinsic dopaminergic somata were observed. The trajectory of the serotonergic large lateral (LL) neuron, a command-like cell for feeding, was documented to project directly to the STN and not to the jaw and pharyngeal musculature as previously reported, thus reopening the important question of how the LL cell activates and coordinates biting activity with pharyngeal swallowing. Additional studies revealed that the LL cell is excited by blood serum applied to the lip and is strongly inhibited by dopamine. These findings provide a new foundation for understanding the regulation and modulation of neural networks involved in feeding.

Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.

The medicinal leech Hirudo verbana has a visceral stomatogastric nervous system of five ganglia; two contain large serotonergic neurons. The serotonergic LL feeding command cell projects directly to this network, where it is excited by blood serum and inhibited by dopamine.

Explore how this research connects to clinical practice

More peer-reviewed studies in Salivary Pharmacology.

• Medicinal leeches and hirudotherapy — Gödekmerdan A et al. (2011)
• PEROXIDATION OF SALIVA LIPIDS IN PATIENTS WITH POSTCOVID SYNDROME DURING HIRUDOTHERAPY — Serikbayeva S et al. (2024)
• Medicinal leech therapy in pain syndromes: a narrative review — Koeppen D, Aurich M, Rampp T (2014)
• Immunomodulatory effects of medicinal leech saliva extract on in vitro activated macrophages — Ayhan H et al. (2024)
• Proteinase inhibitors from the medicinal leech Hirudo medicinalis — Baskova I, Zavalova L (2001)
• Polyfunctionality of destabilase, a lysozyme from a medicinal leech — Baskova I, Zavalova L (2008)
• Make it double: identification and characterization of a Tandem-Hirudin from the Asian medicinal leech Hirudinaria manillensis — Lukas P et al. (2022)
• Use of the medicinal leech in the treatment of ear diseases — Seleznev K et al. (1992)
• Recombinant Destabilase from Hirudo medicinalis Is Able to Dissolve Human Blood Clots In Vitro — Bobrovsky P et al. (2021)
• Effects of Carbon Nanotube Environmental Dispersion on an Aquatic Invertebrate, Hirudo medicinalis — Girardello R et al. (2015)

Browse all ASH-analysed research →