Calretinin-like immunoreactivity in mormyrid and gymnarchid electrosensory and electromotor systems

Abstract

Calretinin-like immunoreactivity was examined in the electrosensory and electromotor systems of the two families of mormyriform electric fish. Mormyrid fish showed the strongest immunoreactivity in the knollenorgan electroreceptor pathway; in the nucleus of the electrosensory lateral line lobe (ELL) and the big cells of the nucleus exterolateralis pars anterior. Mormyromast and ampullary zones of the ELL showed calretinin-like immunoreactivity in the ganglion, granule, and intermediate cell and fiber layers. Mormyromast zones additionally showed labeling of apical dendrites and commissural cells, but the ampullary zone did not. In the electromotor system, two nuclei in the corollary discharge pathway showed labeling: in the paratrigeminal command-associated nucleus and the juxtalobar nucleus. Gymnarchus niloticus (Gymnarchidae) showed strongest calretinin-like immunoreactivity in part of the phase-coding pathway; in S-type electroreceptor afferents. Zones of the ELL not receiving phase-coder input had weak labeling. The electromotor system showed labeling in the lateral relay nucleus and less strongly in the medullary relay nucleus, but none in the pacemaker. The concentration of calcium-binding proteins in mormyrid and gymnarchid time-coding electrosensory pathways is consistent with the hypothesis that they play a role in preserving temporal information across synapses. Cell types that encode temporal characteristics of stimuli in precise spike times have high levels of calcium-binding proteins, but cells that re-code temporal information into presence or magnitude of activity have low levels. Some cell types in the electromotor pathways and early in the time-coding electrosensory pathways do not follow this hypothesis, and therefore preserve temporal information using a mechanism independent of calcium-binding proteins. In particular, electromotor systems may use extensive electrotonic coupling within nuclei to ensure precise timing.

Calretinin immunoreactivity in the brain of the zebrafish, Danio rerio: Distribution and comparison with some neuropeptides and neurotransmitter‐synthesizing enzymes. II. Midbrain, hindbrain, and rostral spinal cord

“…The present results indicate the presence of rather abundant CR‐ir neurons in the torus semicircularis of zebrafish, as well as CR‐ir processes, although they do not form well‐defined layers or differentiated cell populations as observed in the gray mullet (Díaz‐Regueira and Anadón,2000). CR has been observed in neurons of different nuclei of the torus semicircularis of gymnarchids but not in that of mormyrids (Friedman and Kawasaki,1997). In mormyrids, the auditory part of the torus (nucleus medialis dorsalis) receives a rich CR‐ir innervation.…”

“…As regards the Mauthner axon, our results in zebrafish indicate the absence of CR immunoreactivity, which is at variance with that reported in another cyprinid, the tench (Crespo et al,1998). In mormyriformes and gray mullet, the Mauthner axon is also CR negative (Friedman and Kawasaki,1997; Díaz‐Regueira and Anadón,2000).…”

“…The octaval region of zebrafish shows CR‐ir neurons mainly in the magnocellular and the dorsal and ventral tangential octaval nuclei, first described in the cyprinid Leuciscus (Tello,1909). CR‐ir neurons have been observed in some octaval nuclei of mormyriformes (Friedman and Kawasaki,1997) and in the magnocellular nucleus but not in the tangential nucleus of mullet (Díaz‐Regueira and Anadón,2000). These differences probably reflect different specializations of the octaval circuitry in different teleosts.…”

“…In teleosts, the presence of CR in optic fibers and in some neurons of the optic tectum of a cyprinid (Arévalo et al,1995) and in different cells and fibers of the electrosensory system of several mormyriforms (Friedman and Kawasaki,1997) has been reported. A more general study has revealed a number of CR neuronal populations distributed along the brain of an advanced teleost, including various populations in brainstem centers (Díaz‐Regueira and Anadón,2000).…”

Caracterización de los progenitores neurales de retina adulta del pez cebra

“…En peces hay expresión de calretinina 1. Introducción en el techoóptico de tenca (Arévalo et al, 1995) y del pez cebra (Castro et al, 2006;Arenzana et al, 2011), en elárea preóptica de la trucha (Castro et al, 2003) y en las fibras del sistema electrosensorial en peces mormíridos (Friedman y Kawasaki, 1997). En la retina del pez cebra se empieza a expresar a las 48 horas post fecundación, con un marcaje correspondiente a células amacrinas (Arenzana et al, 2011).…”