Serotonergic modulation of the feeding behavior of the medicinal leech

Hungry medicinal leeches, Hirudo medicinalis, bite warm surfaces and ingest blood meals averaging 890% of their weight. Satiation lasts 12-18 months during which leeches avoid warm surfaces and will not bite. The segmental nervous system of the leech is distinguished by a population of neurons which contain serotonin (5-Hydroxytryptamine, 5-HT) at high concentrations. Some of these identified 5-HT neurons directly activate the effectors responsible for three physiological components of feeding: salivary secretion, bite-like movements and pharyngeal peristalsis. A localized warming of the lip is sufficient to initiate ingestion and synaptically excites anterior 5-HT cells into high frequency impulses or bursts. Distension of the body wall terminates ingestion and also hyperpolarizes these 5-HT neurons. Serotonin treatment produces hyperphagic behavior by the leech, while a specific pharmacological lesion of its 5-HT cell produces the anorexic behavior of satiation. This anorexia is transiently reversed by 5-HT treatment. Serotonin plays an obligatory role in the initiation and expression of leech feeding behavior by its differential modulation of central neuronal networks and peripheral glands and muscles.

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

Serotonin neurons directly drive three feeding components in Hirudo medicinalis: salivary secretion, bite-like movements, and pharyngeal peristalsis. Serotonin treatment produces hyperphagia; pharmacological 5-HT lesion produces anorexia of satiation reversible with 5-HT.

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