Retzius cells: neuroeffectors controlling mucus release by the leech

Abstract

Mucus release from the skin of leeches is under the control of the pair of large Retzius cells in each segmental ganglion. The rate of mucus release increases with the impulse activity of Retzius cells and with the concentration of their putative neurotransmitter, 5-hydroxytryptamine, to which the skin is exposed.