Distribution of LHRH-like Immunoreactivity in the Brain of the Japanese Eel (Anguilla japonica) with Special Reference to the Nervus Terminalis

Abstract

The brain of the Japanese eel, Anguilla japonica, was studied immunocytochemically using antisera generated against the synthetic luteinizing hormone-releasing hormone (LHRH) of mammals. LHRH-positive perikarya were observed in both the distal and proximal ganglia of the nervus terminalis and in the ventrolateral portions of the ventral telencephalon and preoptic area. LHRH-positive perikarya of the distal and proximal ganglia of the nervus terminalis sent their fibers to the olfactory nerve, ventral telencephalon, preoptic area, and optic tectum. LHRH-positive fibers, originating from the ventral telencephalon and preoptic area, proceeded toward the olfactory bulb, dorsolateral part of the rostral telencephalon, preoptic area, neurohypophysis, and optic tectum. LHRH-positive fibers were also observed in the optic nerve. These findings are discussed in comparison with recent anatomical findings by others in other teleosts. Further, possible participation of nervus terminalis in reproductive behavior is discussed.