Immunohistochemical localization of serotonin, leu-enkephalin, tyrosine hydroxylase, and substance P within the visceral sensory area of cartilaginous fish

Abstract

We examined the distribution of immunoreactivity to serotonin (5-HT), leu-enkephalin (LENK), tyrosine-hydroxylase (TH), and substance P (SP) within the primary visceral sensory region of cartilaginous fish. Two genera of sharks, Squalus and Heterodontus, a skate, Raja, a ray, Myliobatis, and a holocephalian, Hydrolagus, were used. Cranial nerves, VII, IX, and X enter the visceral sensory complex from the lateral aspect and divide it into lobes. Based on sagittally cut sections, there are four lobes in Hydrolagus and five in Squalus, corresponding to the number of gill arches. The neurochemicals are differentially distributed within each lobe. LENK+ and 5-HT+ fibers are located in all regions within the visceral sensory complex. SP+ fibers are extremely dense in a dorsolateral subdivision and do not extend as far ventrally as 5-HT+ and LENK+ fibers. The lobes lack 5-HT+ cells, but contain a few LENK+ and SP+ cells. Many TH+ cells are distributed in dorsomedial portions of the complex, but there are few TH+ fibers. Thus, the visceral sensory area of cartilaginous fish contains several divisions that can be distinguished by their neurochemical content.

Immunocytochemical evidence for the presence of met‐enkephalin and leu‐enkephalin distinct neurons in the brain of the elasmobranch fish Scyliorhinus canicula

“…The presence of Met-enkephalin in the hypothalamo-neurohypophysial system has been well conserved during vertebrate evolution because it has been found in all groups of tetrapods (De Lanerolle et al, 1981;Merchenthaler et al, 1986Merchenthaler et al, , 1989Reiner, 1987). The distribution of Leu-enkephalin immunoreactivity in Scyliorhinus canicula is in agreement with that previously reported in the brain of other cartilaginous fish such as Squalus acanthias (Northcutt et al, 1988;Stuesse et al, 1992), Heterodontus francisci , and Hydrolagus colliei . In these latter species, however, Leu-enkephalin-like immunoreactivity has also been found in other compartments of the forebrain and brainstem, particularly in the septal area, the area superficialis basalis, the area periventricularis hypothalami, and the reticular nuclei.…”

“…To date, only the Leu-enkephalin form has been detected with immunocytochemical methods in the brain of this group of fish (Northcutt et al, 1988;Stuesse et al, , 1992. In addition, no attempts have been made to determine whether prodynorphin-related end products are present in the central nervous system of cartilaginous fish.…”

“…With cartilaginous fish, a highly specialized and diverse group that diverged from the other fish in the Lower Devonian period, no detailed investigations have been performed to identify the different brain proenkephalin end products. To date, only the Leu-enkephalin form has been detected with immunocytochemical methods in the brain of this group of fish (Northcutt et al, 1988;Stuesse et al, , 1992. In addition, no attempts have been made to determine whether prodynorphin-related end products are present in the central nervous system of cartilaginous fish.…”

Immunocytochemical localization of enkephalins in the brain of the African lungfish, Protopterus annectens, provides evidence for differential distribution of Met‐enkephalin and Leu‐enkephalin

“…lungfish rhombencephalon, Leu-enkephalin-immunoreactive cell bodies were seen in the griseum centrale, the nucleus reticularis, the nucleus of the solitary tract, and the visceral sensory area. This distribution is consonant with that described previously in cartilaginous fish (Stuesse et al, , 1992Vallarino et al, 1994) and amphibians (Merchenthaler et al, 1989). In reptiles and mammals, enkephalinergic cell bodies are located mainly in the raphe nuclei, the locus coeruleus, the nucleus of the solitary tract, and the nucleus caudalis (Naik et al, 1981;Petrusz et al, 1985;Merchenthaler et al, 1986).…”

“…In particular, Met-enkephalin and Leu-enkephalin have been localized in the brain of the elasmobranch fish Scyliorhinus canicula (Vallarino et al, 1994). The distribution of Leu-enkephalin has been described in the telencephalon of the spiny dogfish Squalus acanthias (Northcutt et al, 1988) and in the brainstem of the horn shark Heterodontus francisci (Stuesse et al, , 1992, in Hydrolagus collei Stuesse et al, 1992), and in S. acanthias and Raja binoculata (Stuesse et al, 1992). In contrast, in teleost fish, Met-enkephalin is the only form that has been identified so far, although Leu-enkephalinlike immunoreactivity has been described in the cerebellum of the teleost Carassius auratus by using antisera that cross reacts with Met-enkephalin (Schulman et al, 1981).…”