Journal of Neuroscience, Vol 13, 1577-1587, Copyright © 1993 by Society for Neuroscience
Developmental regulation of segment-specific cholinergic receptors on Retzius neurons in the medicinal leech
WB Kristan Jr, KA French and L Szczupak
Department of Biology, University of California, San Diego, La Jolla 92093.
Retzius (Rz) neurons in the midbody ganglia of medicinal leeches responded
to ACh, applied to their somata, in a manner that depended upon the
neuron's segmental location: Rz neurons in ganglia from midbody segments 5
and 6 [Rz(5,6)] hyperpolarized, whereas Rz neurons from all other segments
[Rz(X)] depolarized. Midbody segments 5 and 6 are notable because they
contain the male and female reproductive organs. Both types of Rz neurons
responded to ACh in a complex way, but the initial phase of each response
appeared to be nicotinic because nicotinic agonists evoked the responses
and nicotinic antagonists blocked them. The reversal potentials of the
responses and the effects of changing the internal and external Cl-
concentration indicated that the hyperpolarizing response of Rz(5,6)
neurons depended upon Cl- whereas the depolarizing response of Rz(X)
neurons did not. The segmentally characteristic responses of Rz neurons
arose during embryonic development. Removing the reproductive ducts [the
peripheral targets of Rz(5,6)] early in embryogenesis caused the Rz(5,6)
neurons to depolarize in response to ACh rather than to hyperpolarize. This
result indicates that development of the characteristic response of Rz
neurons to ACh is strongly influenced by interactions between the neurons
and their appropriate target tissues.