Journal of Neuroscience, Vol 6, 2071-2084, Copyright © 1986 by Society for Neuroscience
Electrophysiological and anatomical identification of the peripheral axons and target tissues of Aplysia neurons R3-14 and their status as multifunctional, multimessenger neurons
AR Rittenhouse and CH Price
The giant neurons R3-14 in the parietovisceral ganglion of Aplysia,
originally proposed to be a homogeneous group of neuroendocrine cells, are
likely candidates for a multifunctional and multiple messenger status. The
studies reported here suggest that individual R3-14 giant neurons not only
innervate specific target tissues but appear to operate more autonomously
than previously thought. Identified members of the group were traced into
peripheral tissues by electrophysiological, autoradiographic, and
intracellular cobalt staining techniques. Five neurons (numbered R6, R7,
R8, R11, and R14) were identified on the basis of their unique patterns of
axonal projections. R6 innervates the ganglionic artery and pericardial
area; R7 and R8, the heart; R11, the kidney; and R14, a large number of
vascular tissues. The wide distribution of R3-14 terminals innervating a
variety of vascular tissues indicates that several general and local
aspects of circulatory physiology are likely to be regulated by these
neurons. R3-14 contain the free amino acid glycine, a putative
neuromodulator that potentiates cardiac and vascular smooth muscle
contraction and several small peptides of unknown, but probably
neurohormonal, function. A model is proposed in which R3-14 release glycine
to modulate local (e.g., hemolymph pressure and distribution)
cardiovascular performance and, indirectly, metabolic homeostasis as well.