Central Projections of the Vagus Nerve in <i>Chelon labrosus </i>Risso (Teleostei, O. Perciformes)

Abstract

The primary projections of the vagus nerve and its nuclei in a perciform teleost, Chelon labrosus, are described after application of hoseradish peroxidase (HRP) labeling and Nissl and silver staining methods. The vagus nerve has three peripheral roots, rostral, medial and caudal, which are formed from viscerosensory and visceromotor rootlets. In addition to viscerosensory and visceromotor rootlets, the caudal root has a cutaneous root and a ‘descending'' root. Dorsally in the caudal root, a fiber bundle enters the medulla from the retroocular and opercular skin region; this bundle joins the descending trigeminal root and courses with it rostrally and caudally. Fibers from another rootlet, which enters dorsolaterally, course caudally towards the spinal cord. This rootlet has not been described in other fishes. The vagal viscerosensory nucleus, where most of the viscerosensory fibers terminate, forms a column in which two types of neurons can be distinguished. The most caudal part of the nucleus is continuous with the commissural nucleus, into which vagal nerve projections also enter. No vagal projections were found in the area postrema. In the visceromotor column, two types of neurons are seen Iateroventral to the IV ventricle.

Calretinin expression in specific neuronal systems in the brain of an advanced teleost, the grey mullet (Chelon labrosus)

“…Another similar feature of mullet and rat is the presence of CR-ir cells in the region of the area postrema, well developed in teleosts including mullets (Morita and Finger, 1987;Díaz-Regueira and Anadón, 1992). Together with the presence of similar neurotransmitters in the area postrema of teleosts and mammals (see Morita and Finger, 1987), the presence of CR in area postrema cells of these distant vertebrates suggests a strong conservation of Ca ϩϩ -buffering mechanisms in this region.…”

Nitric oxide synthase in the glossopharyngeal and vagal afferent pathway of a teleost, Takifugu niphobles

“…In light of retrograde tracing studies in other teleosts (Kanwal and Caprio 1987;Morita and Finger 1987;Díaz-Regueira and Anadón 1992), the lateral portion of the visceral sensory column is probably the site of the branchial afferent termination, whereas the commissural nucleus is the site of the coelomic afferent termination.…”

Development of immunoreactivity to neuropeptide Y in the brain of brown trout (Salmo trutta fario)

“…The hypertrophied visceral areas of the goldfish rhombencephalon (i.e., the facial, glossopharyngeal, and vagal lobes) also contain large numbers of NPY-ir fibers . The caudal portion of the viscerosensory column receives primary afferents from the branchial and visceral branches of the vagus (Lázá r et al, 1992;Díaz-Regueira and Anadón, 1992;Funakoshi et al, 1997) and gives rise to ascending projections to the secondary gustatory nucleus (Finger, 1978;Morita et al, 1983;Finger and Kanwal, 1992;Kotrschal and Finger, 1996;Yoshimoto et al, 1998), which, in turn, projects to the preglomerular nucleus and the nucleus diffusus lobi inferioris hypothalami Lamb and Finger, 1996;Yoshimoto et al, 1998). In trout, the secondary gustatory nucleus receives numerous NPY-ir fibers coursing in the secondary gustatory tract that probably originate in solitary tract/area postrema cells (current results).…”