title: Serotonergic modulation of the feeding behavior of the medicinal leech.
abstract: 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.
mesh_terms: D000818:Animals; D004594:Electrophysiology; D005247:Feeding Behavior / Q000187:drug effects*; D005724:Ganglia / Q000502:physiology; D006651:Histocytochemistry; D007865:Leeches / Q000502:physiology*; D009055:Mouth / Q000502:physiology; D009474:Neurons / Q000032:analysis / Q000145:classification / Q000502:physiology*; D010812:Physical Stimulation; D012701:Serotonin / Q000502:physiology* / Q000633:toxicity; D013696:Temperature; D013997:Time Factors
chemical_list: D012701:Serotonin