Rastogi RK et al. (1998), Comparative analysis of GnRH neuronal systems i...

XB-ART-13850

Gen Comp Endocrinol 1998 Dec 01;1123:330-45. doi: 10.1006/gcen.1998.7144.

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Comparative analysis of GnRH neuronal systems in the amphibian brain.

Rastogi RK , Meyer DL , Pinelli C , Fiorentino M , D'aniello B .

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We have investigated the GnRH-ir neuronal systems in the brain of the oviparous urodele, Triturus vulgaris, ovoviviparous urodele, Salamandra salamandra, and viviparous caecilian, Typhlonectes compressicauda, and have reexamined Xenopus laevis, Ambystoma mexicanum, and Rana esculenta. Results showed that mGnRH neuronal system was diffused along the medioventral telencephalon and diencephalon with the numerical preponderance of GnRH cell bodies in the rostral mediobasal telencephalon in T. vulgaris and S. salamandra and in medial septal area and preoptic area respectively in Typhlonectes compressicauda and X. laevis. The cGnRH-II-ir perikarya were restricted to the midbrain tegmentum in X. laevis and T. compressicauda. In T. vulgaris, two distinct groups of cGnRH-II neurons were distinguished, one in the midbrain tegmentum and another in the paraventricular organ. The former was composed of comparatively bigger perikarya than the latter. In X. laevis brain, besides those in the rostralmost dorsomedial and ventromedial telencephalon and septopreoptic area, mGnRH neurons were also found in the habenulae and habenular commissure as well the infundibular hypothalamus. In A. mexicanum, reexamined, the preoptic area-located mGnRH neurons were distributed in the ependymal lining of the preoptic recess. In this neotenic urodele, furthermore, cGnRH-II neurons were also present in the rhombencephalon, as well as in the infundibular hypothalamus. It is thus clear that while GnRH-ir cell bodies are distributed in the fore-, mid- and hindbrain, their precise neuroanatomical localization varies somewhat within and among groups. Altogether, it is evident that mGnRH neuronal system is confined mainly to the forebrain, whereas cGnRH-II system is commonly found in the mid- and hindbrain. Additional morphological investigations are required to eventually define the functional neuroanatomy of GnRH in the amphibian brain.

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Species referenced: Xenopus laevis
Genes referenced: gnrh1
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	FIG. 6. Schematic, camera lucida-based, lateral profile of mGnRH (black dots and continuous lines) and cGnRH-II (black rhombuses and broken lines) neuronal systems in the brain of Typhlonectes compressicauda (top) and Xenopus laevis (bottom). The two brains are not drawn to the same scale. Lowercase letters indicate the level of transverse sections of T. compressicauda and X. laevis brains illustrated in Figs. 7 and 9, respectively. For abbreviations, see footnote 2.
	FIG. 9. Camera lucida tracings of representative transverse sections of the brain of Xenopus laevis illustrating the distribution of mGnRH and cGnRH-II neurons and fibers. Lowercase letters refer to different planes of transverse sections as shown in Fig. 6. For other details see Fig. 2. For abbreviations, see footnote 2. 313.75.
	FIG. 10. Xenopus laevis brain, transverse sections. (a) Section through habenula (star) and habenular commissure (asterisks) showing mGnRH neurons (arrows) and fibers (cf. Fig. 9d). 3225. (b) Section through anterior preoptic area showing mGnRH neurons (arrows) and dense fiber network (cf. Fig. 9b). 3225. (c) Section through midpreoptic area showing mGnRH neurons (arrows) and dense fiber network. Note immunoreactivity in the ependyma around the preoptic recess (asterisk) (cf. Fig. 9c). 375. (d) Section through midbrain tegmentum showing cGnRH-I neurons (arrows) (cf. Fig. 9e). 3375.