Distribution of gonadotropin-releasing hormone immunoreactive systems in the brain of the Senegalese sole, Solea senegalensis.

Abstract

The present paper reports the immunohistochemical distribution of the gonadotropin-releasing hormone (GnRH) structures in the brain of the Senegalese sole, Solea senegalensis. In this study, we have used two antibodies against the salmon GnRH and chicken GnRH-II forms and the streptavidin-biotin-peroxidase complex method. Immunoreactive cell bodies are observed at the junction between the olfactory bulbs and the telencephalon (terminal nerve ganglion cells), in the ventral telencephalon, in the preoptic parvocellular nucleus, and in the synencephalic nucleus of the medial longitudinal fasciculus. GnRH-immunoreactive fibres were found extensively throughout the brain, located in the telencephalon, preoptic area, hypothalamus, hypophysis, optic tectum, midbrain and rhombencephalon. The antisera used in this study against the two GnRH forms exhibited cross-reactivity on the same cell masses and did not allow cell populations expressing different GnRH forms to be discriminated clearly. However, anti-salmon GnRH immunostained the GnRH cells and fibres of the forebrain much more intensely, whereas the anti-chicken GnRH antiserum shows a higher immunoreactivity on synencephalic cells of the medial longitudinal fasciculus.