Journal of Neuroscience, Vol 10, 1226-1240, Copyright © 1990 by Society for Neuroscience
Descending control of electroreception. I. Properties of nucleus praeeminentialis neurons projecting indirectly to the electrosensory lateral line lobe
J Bastian and B Bratton
Department of Zoology, University of Oklahoma, Norman 73019.
The first-order CNS processing region within the electrosensory system, the
electrosensory lateral line lobe, receives massive descending inputs from
the nucleus praeeminentialis as well as the primary afferent projection.
The n. praeeminentialis receives its input from the electrosensory lateral
line lobe as well as from higher centers; hence this nucleus occupies an
important position in a feedback loop within the electrosensory system.
This report describes the physiological properties of a category of n.
praeeminentialis neurons characterized by very high spontaneous firing
frequency, but relatively poor sensitivity to electrolocation targets as
compared to neurons in the electrosensory lateral line lobe. These neurons
are specialized to encode long-term changes in electric organ discharge
amplitude with high resolution. Intracellular recording and Lucifer yellow
staining of these neurons show that they are the previously described
multipolar neurons of the n. praeeminentialis, and they project bilaterally
to the posterior eminentia granularis. Posterior eminentia granularis
efferents project to the electrosensory lateral line lobe forming its
dorsal molecular layer. Hence, these multipolar cells influence the
electrosensory lateral line lobe circuitry indirectly. The information that
the multipolar cells encode regarding the electric organ discharge
amplitude may be needed for a gain control mechanism operative within the
electrosensory lateral line lobe. Previous studies have shown that the
indirect projection from the n. praeeminentialis to the electrosensory
lateral line lobe must be intact for this gain control mechanism to
operate.