Selective decrease in immunoreactive somatostatin in rat intermediate pituitary lobe after stalk section.

Immunoreactive somatostatin is present in the intermediate pituitary lobe of the rat and, to a lesser extent, in the posterior lobe. Section of the pituitary stalk results in a marked (80%) decrease in somatostatin in the intermediate pituitary lobe, but no change in the peptide levels in the posterior lobe. These results indicate that a substantial part of intermediate lobe somatostatin is located in nerve fibers originated in the brain.