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Since the cell bodies of leech neurons are free of synapses, the receptors that give rise to these responses are extrasynaptic.
These highly specific expression patterns are consistent with the hypothesis that leech netrin plays a role in forming the major interganglionic neuronal tracts and in defining ventral versus dorsal domains of peripheral innervation.
Well-fed leeches do not normally bite, but a brief bath in 5-HT will evoke biting behavior by them as well.5.Serotonin is localized to a limited population of identifiable neurons in the C. N. S., and plays a pivotal and mandatory role in organizing the feeding behavior of the medicinal leech.
These findings identify a set of candidate guidance cells for axonal outgrowth in the leech, similar to those previously described in the developing nervous system of insects.
These results demonstrate that cholinergic motoneurons can be differentiated from other cells in the leech nervous system by their high intracellular concentration of AChE.
These neurons are likely to mediate swim cessation caused by cell Tr2 activity, and thus play the role of intermediate control cells in the leech CNS.
The results account for distinctive features of successful repair in the adult leech, where axonal sprouting and target selection can be influenced by unequal competition between neurons.
Another substrate, promoting even more extensive sprouting of leech neurons, is cell-free extracellular matrix obtained from leech ganglion capsules.
These results provide evidence that adult DL and VL leech neurons retain intrinsic information for determining a variety of their properties in culture: In particular, they reproduce type-specific neuritic patterns in the absence of extrinsic guidance cues.
The leech CNS has expanded our understanding of how the nervous system produces behavior and continues to serve as an excellent model in this endeavor.
Thus, the leech brain may represent a simple model for the study of these enzymes.
This makes the leech exceptionally attractive for neuroethological studies because it is one of the simplest organisms in which the methods of psychology and neurobiology can be combined.
The data imply the existence of two kinds of Na channels in normal, fully differentiated leech neurons.

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