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 se...

Cloned cDNAs have been isolated that encode a variant of hirudin, a potent thrombin inhibitor that is secreted by the salivary glands of the medicinal leech, Hirudo medicinalis. This variant probably corresponds to a form that has been purified from leech heads but differs in amino acid sequence from the hirudin purified from whole leeches. There are at least three hirudin transcripts detectabl...

Receptor protein tyrosine phosphatases (rPTPs) are thought to play a crucial role in neuronal development, particularly in pathfinding by growing processes. We have cloned and sequenced two Hirudo medicinalis rPTPs that are homologous to the Drosophila and vertebrate rPTPs of the Leukocyte common antigen-related (LAR) subfamily. These Hirudo rPTPs, HmLAR1 and HmLAR2, are products of different, ...

The inhibition of serine proteinases by both synthetic and natural inhibitors has been widely studied. Eglin c is a small thermostable protein isolated from the leech, Hirudo medicinalis. Eglin c is a potent serine proteinase inhibitor. The three-dimensional structure of native eglin and of its complexes with a number of proteinases are known. We here describe the crystal structure of hydrolyse...

T hrough evolution, several animal species have been endowed with salivary anticoagulants, presumably to secure their nutritional requirements for fluid blood from their prey. It has been known for centuries that the bites of leeches, certain snakes, insects, and vampire bats can result in local and systemic bleeding. The use of the medicinal leech, Hirudo medicinalis, for therapeutic bloodlett...

We have previously demonstrated that the shortening reflex of the leech Hirudo medicinalis displays habituation, dishabituation, and sensitization. In this paper we demonstrate that the shortening reflex of the semi-intact animal also displays these phenomena. In the first experiment we found that the magnitude of the touch-elicited shortening reflex decreased as a result of repeated stimulatio...

Two tubular hearts propel blood through the closed circulatory system of the medicinal leech. The hearts are myogenic but are driven by a centrally generated motor pattern that controls heart rate and intersegmental coordination. In two consecutive papers, we address the question of how the motor pattern is translated into the pattern of diastole and systole of leech hearts. We imaged the const...

The whole-body shortening reflex of the medicinal leech Hirudo medicinalis is a withdrawal response produced by anterior mechanical stimuli. The interneuronal pathways underlying this reflex consist of the S cell network (a chain of electrically coupled interneurons) and a set of other, parallel pathways. We used a variety of techniques to characterize these interneuronal pathways further, incl...