Specificity of Connections Formed by Nociceptive Cells of the Leech in Tissue Culture

Individual medial and lateral nociceptive (N) cells of the leech have been paired with a variety of different target cells to determine the patterns and the properties of the connections made in culture. 1. Lateral nociceptive N cells did not make electrical or chemical connections with other N cells or with P sensory cells. 2. N cells made electrical connections with Retzius cells, anterior pagoda cells (AP) and annulus erector (AE) and L motor neurones in culture. 3. Lateral and medial N cells, which differ in the animal, exhibited consistent differences in culture. Well-established electrical junctions made by lateral N cells showed clear rectification. In contrast, medial N cells could make either nonrectifying or rectifying connections with target cells. 4. In spite of the presence of strong electrical coupling, evidence for chemically mediated synaptic interactions between N cells and other neurones was obtained on occasion. 5. These findings emphasize the specific nature of connections formed in culture. Unlike P sensory cells, N cells in culture did become electrically connected to Retzius cells and could make both rectifying and non-rectifying electrical junctions with appropriate targets.