Abstract
ABSTRACT Topological and histological descriptions of the preoptic area and hypothalamus of the cardinal tetra Paracheirodon axelrodi were performed. Standard histological paraffin sections were used and stained with Nissl technique, and plastic sections for high-resolution optic microscopy (HROM). The preoptic area showed some differences related to the location of the magnocellular preoptic nucleus (PM) and the size of the neurons in this region, as they were the biggest in all the preoptic area. Additionally, within the preoptic area, the different structures that comprise the organum vasculosum of the lamina terminalis (OVLT) were identified and characterized. The hypothalamus could be subdivided in three regions - the ventral, the dorsal and the caudal hypothalamic regions - neuron morphology, size and staining pattern were similar in all of them.
Highlights
The teleost central nervous system (CNS) plays an important role in the regulation of reproduction
Studies in teleost fish have shown that the regulation of hypophysiary activity is not restricted to the hypothalamus, as it was once believed, but it extends to other brain areas such as the ventral telencephalon and the preoptic area (Kah et al, 1993; Trudeau et al, 1997)
The preoptic area in P. axelrodi extends from the medial region of the ventral telencephalon to the beginning of the diencephalon (Fig. 1)
Summary
The teleost central nervous system (CNS) plays an important role in the regulation of reproduction. It integrates environmental signals received through the sensorial system and internal signals regulated by the hypophysiotropic system. Studies in teleost fish have shown that the regulation of hypophysiary activity is not restricted to the hypothalamus, as it was once believed, but it extends to other brain areas such as the ventral telencephalon and the preoptic area (Kah et al, 1993; Trudeau et al, 1997). The two main areas in the anterior-ventral brain containing neuronal somas whose axons reach the neurohypophysis in teleost fishes are the preoptic area and the hypothalamus (Palay, 1945)
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