5-HT-like immunoreactivity in the brains of plethodontid and salamandrid salamanders ( Hydromantes italicus , Hydromantes genei , Plethodon jordani , Desmognathus ochrophaeus , Pleurodeles waltl ): an immunohistochemical and biocytin double-labelling study

Abstract

The distribution of 5-HT-like-immunoreactive cell bodies and fibres was studied in the brains of the salamanders Hydromantes italicus, H. genei, Plethodon jordani, Desmognathus ochrophaeus (family Plethodontidae), and Pleurodeles waltl (family Salamandridae). In addition, double-labelling experiments with biocytin were carried out to identify the relationship between serotonergic fibres and neurons involved in the processing of sensory and sensorimotor information. In all species, 5-HT-immunopositive somata are found in the ventral thalamus close to the ventricle forming the paraventricular organ. In the hypothalamus, cells are labelled in the ependymal layer around the infundibular recess and at the lateral edge of the periventricular grey. In the pretectum, a few immunoreactive cells are situated dorsolaterally in the grey matter. In the tegmentum and medulla oblongata, cells of the raphe nuclei are regularly distributed along the midline; labelled perikarya are occasionally found in the cervical spinal cord. 5-HT-like-immunoreactive fibres are widely distributed throughout the nervous system. Densely arborizing fibres are found in the olfactory bulb, striatum and amygdala. Distinct fibre projections extend in the ventral thalamus and tectum. Biocytin tracing of striatal and tectal projection neurons and ascending reticular neurons combined with the demonstration of 5-HT suggest that the striatum, the tectum and the ascending activating system are strongly influenced by 5-HT.

Serotonergic systems in the spinal cord of the amphibian urodele Pleurodeles waltl

“…The course of some longitudinal fibers (arrows) can also be followed in the ventral white matter. processes that extend ventrally into the spinal cord, where they enter the white matter and run laterally (Dicke et al, 1997). This study further mentions that the raphe nuclei extends without interruption to the level of the obex and that, in the caudal part of the medulla oblongata, the number of 5-HT-labeled neurons decreases continuously along the spinal cord.…”

“…These differences in the ability of 5-HT to elicit a locomotor pattern may therefore reflect interspecies differences, although methodological and animal developmental stage differences cannot be ruled out (see Cazalets et al, 1992;Jovanovic et al, 1996). (Dubé and Parent, 1982;Kah and Chambolle, 1983;Fasolo et al, 1986;Corio et al, 1992;Clairambault et al, 1994;Dicke et al, 1997). A previous study reported that, in P. waltl, neurons of the raphe nuclei are the source of 5-HT-ir (vlp).…”

Connectivity and cytoarchitecture of the ventral telencephalon in the salamander Plethodon shermani

“…However, the knowledge of the urodele ventral telencephalon derives mostly from interpretations of anatomical observations of normal brain morphology (Fish, 1895;Herrick, 1910Herrick, [and references therein], 1921Herrick, , 1948Northcutt and Kicliter, 1980) and histochemistry (Dubé and Parent, 1982;Taban and Cathieni, 1983;Fasolo et al, 1990;Smeets, 1991, 1992;NaujoksManteuffel et al, 1994;Dicke et al, 1997;Lowry et al, 1997;Marín et al, 1997bMarín et al, , 1998Beltramo et al, 1998). The few experimental studies conducted in salamanders give only a partial picture of the ventral telencephalon (Kokoros and Northcutt, 1977;Finkenstä dt et al, 1983;Himstedt, 1986, 1988;Naujoks-Manteuffel and Manteuffel, 1988;Dubé et al, 1990;Fasolo et al, 1990;Sassoè-Pognetto et al, 1995;Marín et al, 1997a,c;Dicke et al, 1998;Roth and Grunwald, 2000).…”

Distinction of Neurochemistry between the Cores and Their Shells of Auditory Nuclei in Tetrapod Species

“…Several studies have investigated the distribution of ENK, SP and 5-HT in the brain of amphibians, although few have focused on the subdivisions of auditory areas [Merchenthaler et al, 1987[Merchenthaler et al, , 1989Adli et al, 1988Adli et al, , 1999Lázár et al, 1990;Humphrey et al, 1995;Dicke et al, 1997;Endepols at al., 2000]. Despite the different species used, our results were largely consistent with a report of Endepols et al [2000] that describes the chemoarchitecture of auditory midbrain.…”