Journal of Neuroscience, Vol 10, 361-369, Copyright © 1990 by Society for Neuroscience
The effects of postembryonic receptor cell addition on the response properties of electroreceptive afferents
DY Sanchez and HH Zakon
Department of Zoology, Patterson Laboratory, University of Texas, Austin 78712.
The weakly electric fish Sternopygus detects electric fields with a
receptor organ called a tuberous electroreceptor. Previous studies have
shown that an electroreceptive afferent fiber innervates a single organ in
small fish and that as fish grow some of these organs divide, giving rise
to daughter organs; these divide in turn to produce a cluster of organs.
All of the organs in a cluster are innervated by the original afferent,
which sprouts new terminals to accommodate them. Other organs, however,
seldom divide. Thus, the distribution of the number of tuberous organs per
afferent becomes increasingly bimodal with fish body length (Zakon, 1984a).
In order to investigate the effect of organ addition on neural coding
within the afferent fiber, activity was recorded from single units within
the anterior branch of the anterior lateral line nerve in fish of a range
of sizes. It was found that, as fish increase in body length, the best
frequency, sharpness of tuning, and sensitivity increase in a subset of
afferents, while others remain essentially unchanged. This results in an
increasingly bimodal distribution of these physiological measures with
increasing fish body length. These results suggest that the afferents that
innervate multiple receptor organs are more sensitive and possess higher
best frequencies than those that innervate 1 or 2 organs. This was
confirmed by dye injections of electroreceptive fibers with Lucifer
yellow.(ABSTRACT TRUNCATED AT 250 WORDS)