Varicosity-associated antigens define neuropile subfields in the leech central nervous system.

A panel of twelve monoclonal antibodies raised against homogenates of leech nerve cords and four polyclonal antisera raised against purified neurotransmitters were used to label varicosities immunocytologically in the central neuropile of leech segmental ganglia. These immunoreactive varicosities occur in distinct patterns, some of which have a simple geometry. Three antibodies label immunoreactive varicosities distributed in a single dorsoventrally-oriented plane, two label varicosities distributed in lateral hemi-neuropiles (leaving void a central cephalocaudal passageway), and five label varicosities distributed throughout the neuropile. Six antibodies tested label varicosities across leech species, and five of these varicosity populations are distributed in patterns conserved across leech species. Immunocytologically-defined neuropile subfields do not correspond with previously identified histological and ultrastructural features of leech segmental ganglia. Analysis of immunocytologically-defined subfields is extended to include identification of sets of neurons which appear to project into these subfields, and to include an intracellular characterization of one of these neuron sets.