Substance P in the habenulo-interpeduncular system of the goldfish.

The distribution of substance P (SP)-like immunoreactivity has been studied in the habenulo-interpeduncular system of the goldfish in normal conditions and after habenular ablation. In normal conditions intense SP-like immunoreactivity was observed in the neuropilar structure of the interpeduncular nucleus (IPN). No SP-like immunoreactive cell bodies were observed in the habenular nuclei (HBN), but some SP-like immunoreactive fibres were localized in the central core of the nucleus. Following surgical habenular ablation SP-like immunoreactivity was reduced in the IPN. The image analysis performed on the IPN showed clear-cut transmittance changes in the area examined. The results suggest that SP is involved in connecting HBN and IPN in goldfish, and are consistent with the data of mammals and other vertebrates.