Postactivation inhibition of spontaneously active neurosecretory neurons in the medicinal leech

Spontaneously active neurosecretory neurons in vertebrate and invertebrate nervous systems share similarities in firing frequencies, spike shapes, inhibition by the transmitters they themselves release and postactivation inhibition, an intensity-dependent period of suppressed spontaneous generation of action potentials following phases of high-frequency activity. High-frequency activation of spontaneously active serotonin-containing Retzius cells in isolated ganglia of the leech Hirudo medicinalis induced prolonged membrane hyperpolarisations causing periods of postactivation inhibition of up to 33 s. The duration of the inhibitory periods was directly related to both the number and rate of spikes during activation and was inversely proportional to a cell's spontaneous firing frequency. The periods of postactivation inhibition remained unaffected by both serotonin depletion through repeated injections of 5,7-dihydroxytryptamine and suppressing the afterhyperpolarisation following each action potential with tetraethylammonium (TEA), iberiotoxin or charybdotoxin, suggesting that neither autoinhibition by synaptic release of serotonin nor calcium-activated potassium channels contribute to the underlying mechanism. In contrast, the postactivation inhibitory period was significantly affected both by differential electrical stimulation of the same Retzius cells via microelectrodes filled with molar concentrations of either Na(+)-acetate or K(+)-acetate, and by partial inhibition of Na(+)/K(+)-ATPase with ouabain. Thus, postactivation inhibition in Retzius cells results from prolonged hyperpolarising activity of Na(+)/K(+)-ATPase stimulated by the accumulation of cytosolic Na(+ )during phases of high-frequency spike activity.

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

In isolated Hirudo medicinalis ganglia, high-frequency activation of serotonin-containing Retzius cells produced postactivation inhibition up to 33 s; experiments excluding serotonin autoinhibition and calcium-activated potassium channels implicated Na+/K+-ATPase driven by cytosolic sodium accumulation.

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 →