ULTRASTRUCTURAL AND IMMUNOHISTOCHEMICAL STUDY OF THE TELENCEPHALO-HABENULO-INTERPEDUNCULAR CONNECTIONS OF THE GOLDFISH

Surgical ablations of telencephalon or telencephalon plus habenular nu clei (HBN) have been performed for studying anatomical connections of the telencephalo-habenulo- interpeduncular system of the goldfish. The results of the ultrastructural studies confirmed the presence of mass ive telencephalo-habenular and habenulo-interpeduncular projections an d, in addition, demonstrated a minor direct telencephalo-interpeduncul ar connection. Immunohistochemical localization of substance P in the interpeduncular nucleus (IPN) after telencephalic ablation failed to d emonstrate the involvement of this neurotransmitter in the direct tele ncephalo-interpeduncular projection, while telencephalon plus HBN abla tion reduced substance P immunoreactivity in the IPN. The different di stribution of degenerating terminals converging on the IPN from the HB N and from the telencephalon suggested a subnuclear organization of th is area, as described in mammals.