Central Synaptic Inputs to Identified Leech Neurons Determined by Peripheral Targets

Abstract

Developing Retzius (Rz) neurons in different segments of the central nervous system of the medicinal leech have different peripheral targets: Rz cells in standard segments innervate the body wall, whereas Rz cells in the reproductive segments innervate reproductive tissue. Early removal of reproductive tissue primordia causes reproductive Rz cells to develop morphologically like their standard segmental homologs, suggesting that Rz cells depend on peripheral targets for signals that determine their central and peripheral morphology. Furthermore, after removal of reproductive tissue, reproductive Rz cells also receive synaptic inputs normally appropriate for standard Rz cells. These results suggest that the functional identity of these neurons is specified by the target they contact during embryogenesis.

Localization of the myomodulin-like immunoreactivity in the leech CNS

“…However, the differential staining pattern is consistent with other differences previously reported for the R cells in ganglia 5 and 6 (French and Kristan, 1992). For example several properties of the R cells in ganglia 5 and 6 are different from those in other segmental ganglia, such as smaller cell bodies and restricted dendritic branchings within the neuropil (Jellieset al, 1987;Macagnoetal., 1986), different peripheral targets (Glover and Mason, 1986), differential responding to P-cell stimulation, and ACh application (Kristan and French, 1988;Loer and Kristan, 1989;Wittenberg et al, 1990).…”

Morphological plasticity of motor axons in Drosophila mutants with altered excitability

“…In recent years, however, studies of long-term physiological and anatomical changes in Aplysia during behav-ioral conditioning (Kandel et al, 1986;Bailey and Chen, 1988a,b), as well as studies of regeneration (Murphey and Lemere, 1984;Shepherd and Murphey, 1986;Loer et al, 1987;Loer and Kristan, 1989) have changed this view. Instead, it has become apparent that, even though the behavioral repertoire of invertebrates is less complex than that of vertebrates, developmental and physiological plasticity is a common feature (reviewed in Lnenicka and Murphey, 1989; see also Technau, 1984;Meinertzhagen, 1989).…”

Segmental diversification of an identified leech neuron correlates with the segmental domain in which it expresseslox2, a member of the hox gene family

“…For instance the boundaries already described can be explained by assuming that some other, as yet unidentified Hox gene or genes are expressed by MPS in a different but overlapping segmental domain. Alternatively, one could envision that the MlO/ 11 and M17/ 18 boundaries in MPS phenotype are independent of Hox gene expression and may depend on cell interactions that occur after these neurons innervate their targets (Loer and Kristan, 1989).…”