Morphological changes associated with stretch in a mechano-receptor.

The S neurons of decapod crustacean coxal receptors respond to a constant stimulus with a steady-state response lasting for at least 20 min. This property makes it possible to fix neurons in the stretched or relaxed condition by rotating and pinning the coxa up or down respectively. In specimens perfused with 5 mM lanthanum chloride before fixation, it was found that the extracellular space around the nerve terminals, particularly the naked tubular endings, is open to ions. The cross-sections of the tubular processes (dendritic fingers) are about 25% smaller in stretched specimens, and the secondary dendritic branches connecting the fingers with the remainder of the dendrite appear shorter and thicker. The presence of mitochondria at the periphery of the main part of the dendrite and in the secondary branches, but not in the fingers, is interpreted as evidence for an electrical model similar to that proposed for vertebrate photoreceptors. The observed morphological effects of stretch are discussed in terms of this model.