Regeneration of a central synapse restores nonassociative learning

Sensitization is a form of nonassociative learning in which a strong or noxious stimulus persistently enhances the response produced by a weaker stimulus. In the leech Hirudo medicinalis, the S-interneuron is required for sensitization of the shortening response. A single S-cell axon was surgically separated from its sole synaptic partner, the neighboring S-cell. This consistently eliminated sensitization without impairing reflexive shortening itself, as measured in semi-intact specimens. Sensitization of the shortening reflex returned after 3 weeks when the severed axon grew and regenerated its specific electrical synapse within the nerve cord, as shown by restored conduction of impulses between S-cells. This confirms the essential role of one neuron, the S-cell, in sensitization, and it demonstrates that regeneration of the synapse between S-cells restores this example of nonassociative learning.

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

In Hirudo medicinalis, surgically separating the S-interneuron from its synaptic partner abolishes sensitization (a form of nonassociative learning); synaptic regeneration restores the behavior — directly linking a single synapse to a learned behavior.

Explore how this research connects to clinical practice

More peer-reviewed studies in Genomics & Proteomics.

• Leech Salivary Proteome and Transcriptome: 434 Deduced Protein Sequences — Liu Z, Tong X, Su Y, et al. (2019)
• Medicinal Leech Draft Genome — Anticoagulant Gene Survey — Kvist S, Manzano-Marín A, de Carle D, Trontelj P, Siddall ME (2020)
• Leech therapy (Hirudo medicinalis) attenuates testicular damages induced by testicular ischemia/reperfusion in an animal model — Davoodi F et al. (2021)
• New anticoagulant protein from medicinal leech — Manuvera V et al. (2024)
• AIF-1 and RNASET2 Play Complementary Roles in the Innate Immune Response of Medicinal Leech — Baranzini N et al. (2019)
• Medicinal leech antimicrobial peptides lacking toxicity represent a promising alternative strategy to combat antibiotic-resistant pathogens — Grafskaia E et al. (2019)
• Structural insights into thrombolytic activity of destabilase from medicinal leech — Marin E et al. (2023)
• The genome of medicinal leech (Whitmania pigra) and comparative genomic study for exploration of bioactive ingredients — Tong L et al. (2022)
• Medicinal Leech CNS as a Model for Exosome Studies in the Crosstalk between Microglia and Neurons — Raffo-Romero A et al. (2018)
• Transcriptomic profiling and the first spatial expression analysis of candidate genes in the salivary gland of the East Asian medicinal leech, Hirudo nipponia — Kim J et al. (2024)

Browse all ASH-analysed research →