[Somatostatin in lamprey brains (Lampetra planeri Bloch)]

In the brain of larval and adult lampreys (Lampetra planeri Bloch) a distinct somatostatin system using somatostatin antiserum with the unlabeled peroxidase-antiperoxidase technique was demonstrated. The immune reactive perikarya are localized in the nucleus ventralis hypothalami and they are restricted to this nucleus without exception. A small number of immune positive efferences invades the commissura praeinfundibularis. In the neurohypophysis localized caudally from this commissure and in the adenohypophysis no somatostatin fibres could be visualized. Most of the efferences leave the hypothalamus as exohypothalamic fibres and form a system of somatostatin fibres which extends from the telencephalon to the medulla oblongata. Regionally, this system is organized in a net-like manner.