Interspecies differences in the substance P- and vasoactive intestinal polypeptide-like immunoreactivities in the olfactory bulb of Salmo gairdneri and Barbus meridionalis

Substance P-, F8Famide-, and A18Famide-like immunoreactivity in the nervus terminalis and retina of the goldfish Carassius auratus

We re-investigated the occurrence of substance P-like immunoreactivity in the retina of the goldfish Carassius auratus using antisera to substance P and other tachykinins. Most antisera labelled a previously described single class of mono-stratified amacrine cells arborizing in layer 3 of the inner plexiform layer. Preabsorption experiments showed that these amacrine cells contained at least one tachykinin-like peptide. One antiserum (INC 353) to substance P labelled not only these amacrine cells but also fibres in layer 1 of the inner plexiform layer and fibres in the optic nerve. These fibres were identified as retinopetal projections of the nervus terminalis, in part because of colocalized labelling with antisera against gonadotropin-releasing hormone and FMRFamide. Preabsorption experiments showed that the substance P-immunoreactive material in the nervus terminalis was not substance P or any other typical tachykinin. Labelling of the nervus terminalis with INC 353 was blocked by preabsorption with two bovine FMRF-amide-like peptides, F8Famide and A18Famide, which contain a substance P(4-7)-like region. Antisera to F8Famide and A18Famide strongly labelled ganglia of the nervus terminalis and retinopetal fibres. We suggest that labelling of the nervus terminalis by antisera to substance P and FMRFamide occurs because of homologies between these antigens and a non-tachykinin, endogenous peptide that is similar to F8Famide and A18Famide.

Immunocytochemical identification of primary olfactory afferents in rainbow trout

We have used a combination of techniques to analyze the primary olfactory projection in trout: anterograde tract tracing with horseradish peroxidase (HRP) and immunocytochemistry with antisera to olfactory marker protein (OMP) and to keyhole limpet hemocyanin (KLH). HRP labeling and the OMP antiserum revealed a subset of ciliated receptor neurons with a wide dendrite that lacked the protruding knob found on other receptor neurons. The organization of the primary olfactory axons was clearly revealed by antisera to KLH, which reacted with no other neurons. When visualized with anti-KLH, fascicles of olfactory axons penetrated the basal lamina of the olfactory rosette at scattered sites and converged to form the olfactory nerve. Fascicles within the olfactory nerve traveled parallel to the long axis of the nerve until resorted by extensive intermixing as they entered the olfactory bulb. Within the olfactory bulb, most axons terminated in nine discrete terminal fields in the glomerular layer; however, a few olfactory nerve axons projected into the ventral medial telencephalon. Fascicles supplying each terminal field in the glomerular layer followed distinctive trajectories within the olfactory nerve layer. Axons ending in two terminal fields made brush-like terminations rather than the glomerular terminations characteristic of the remaining seven fields. After unilateral olfactory nerve transection, returning olfactory axons reestablished the normal pattern of terminal fields within 14 weeks. It is likely that the organization of afferents in the trout olfactory bulb is similarly well regulated during normal receptor cell replacement.

The development of substance P-like immunoreactivity in the goldfish brain

The development of substance P-like immunoreactivity (SPLI) in the goldfish brain was studied by means of the indirect peroxidase-antiperoxidase technique and an antibody to substance P. By 80 h after fertilization, the first SPLI-cell bodies appear in the ventricular zone of the future diencephalon and the first SPLI-fibers appear in the olfactory bulbs. Two days after hatching (which occurs at 100 h after fertilization), SPLI fibers connecting the olfactory bulbs and hypothalamus are seen. In the optic tectum SPLI-fibers appear for the first time 5 days after hatching. In the brain stem, SPLI-cell bodies appear in juvenile animals 40 days after hatching. The highest number and intensity of SPLI-cell bodies and fibers are found in the area postrema. SPLI-cell bodies are also seen in the gustatory nucleus, nucleus ambiguous, reticular formation of the medulla, dorsal motor nucleus of the vagus and commissural nucleus of Cajal. The significant information gained from the present study is: 1. The rostro-caudal sequence in which the SPLI appears in the developing nuclei of the goldfish brain 2. The reduction of SPLI-cell bodies in some nuclei with age Thus, in the brain stem, SPLI-cell bodies that were labeled in juvenile goldfish were not seen in adults. This might be due to changes in the rate of axonal transport, changes of the SP phenotype during development or cell death. The developmental sequence and relative timing in which SPLI-cell bodies appear in the goldfish, rat and mice are similar.

Substance P-like immunoreactivity in the brain of the gymnotiform fish Apteronotus leptorhynchus: presence of sex differences

The distribution of substance P-like immunoreactivity (SPli) was charted in the brain of the gymnotiform fish Apteronotus leptorhynchus, and correlated with the circuitry underlying intraspecific electrocommunication. Cell bodies were found predominantly in the lateral hypothalamus and in certain paraventricular organs: nucleus preopticus periventricularis, anterior subdivision; anterior hypothalamus; nucleus posterioris periventricularis; nucleus recessus lateralis, medial subdivision 2; nucleus recessus posterioris and nucleus recessus lateralis, lateral subdivision. Cell bodies were also found in the rostral olfactory nucleus, ventral telencephalon (ventral and central subdivisions), the habenula, the vagal sensory and motor nuclei and in the subtrigeminal nucleus. The distribution of SPli fibers was similar in some respects to that reported for other vertebrates. SPli was found in the rhombencephalon associated with vagal afferent fibers and in the funicular nucleus (possibly related to nociception). In the diencephalon and midbrain SPli fibers were found in the habenular-interpeduncular tract, in the hypothalamus and pituitary. SPli fibers were also found in preoptic and forebrain areas. The most striking result was the sexually dimorphic SPli innervation of certain hypothalamic and septal nuclei, and of the prepacemaker nucleus (PPn), a diencephalic cell group which controls communication ('chirping') in gymnotiforms. The PPn and septal/hypothalamic nuclei were densely innervated by SPli in males but devoid of SPli in females.

An immunocytochemical study of the development of the olfactory system in the three-spined stickleback (Gasterosteus aculeatus L., Teleostei)

Antisera against a variety of substances have been found to produce an identical immunoreaction in the developing olfactory system of a teleost, the three-spined stickleback (Gasterosteus aculeatus). The label is localized in the olfactory placode, the olfactory nerve and those parts of the secondary olfactory tracts which constitute the dorsal descending fascicles and the ventral descending fibers of the medial olfactory tract. The label was first detected 3 days after fertilization (3D) in the olfactory placode where labeled supporting cells were observed. At 4D, the label was observed at the site of the developing olfactory bulbs. At 7D, the olfactory placode lost the direct contact with the brain and the labeled olfactory nerve became visible. At the same time, the medial olfactory tract emerged from the bulbs, and contacts with cells in the nucleus of the terminal nerve were observed. The development of the medial olfactory tract proceeded caudally, and by the end of 10D, the olfactory tract reached the periventricular hypothalamus. Pre-absorption of the antisera with the respective antigens did not abolish the capacity of the antisera to produce the label. The immunoreaction is thus not specific for the antigens against which the antisera have been raised. Yet the label produced by the immunoreaction is an extremely reliable marker for the primary olfactory tract, and the only existing marker by which secondary olfactory tracts can be visualized.