Distribution of somatostatin-immunoreactive structures in the central nervous system of the frog, Rana esculenta

The distribution of somatostatin-containing structures in the central nervous system of the frog, Rana esculenta, was studied using the peroxidase immunohistochemical method. Immunoreactive elements were widely distributed in several regions of the central nervous system. With the exception of the primordium hippocampi, where a few stained perikarya were revealed, the pallium were free of immunoreactivity. In subcortical regions of the telencephalon, immunoreactive varicose fibers were observed in the septum and the amygdala, thin fibers were found in the lateral forebrain bundle, and patchy distribution of immunoreactivity was revealed in the striatum. A large number of immunostained perikarya was observed in the hypothalamus, the thalamus, and the preoptic and suprachiasmatic nuclei. Intensely stained CSF-contracting neurones were present among the ependymal cells in the preoptic recess. In the midbrain, the optic tectum and tegmental nuclei contained immunoreactive cell bodies and fibers, and an elongated dense bundle of fibers was detected in the basal area along the midline. In the hindbrain, the subventricular gray matter was rich in strongly stained cell bodies and fibers, and the nucleus of solitary tract presented moderately stained neurons. At different levels of the spinal cord, immunoreactive cell bodies were revealed in lamina X dorsal to the central canal, and scattered nerve fibers were shown in the superficial dorsal horn.