Galanin immunoreactive innervations of the anterior pituitary in the monkey and the dog

As we know, the anterior pituitary is regulated by hypothalamic hormones via the portal system. However, our recent studies have demonstrated the presence of a substantial amount of substance P (SP)- and calcitonin gene-related peptide (CGRP)-containing nerve fibers in the anterior pituitary. In the present paper, the existence of a considerable amount of galanin (GAL)like immunoreactive (ir) nerve fibers with numerous of varicosities in the anterior pituitaries of the Macaca mulatta monkey and the dog were reported. In the monkey, GAL-ir nerve fibers with a large amount of varicosities were mainly located in the medial part of the gland, dominantly in its dorso-posterior regions. A great majority of varicosities were found to be closely related to the glandular tissue although some were located along the walls of blood sinus. GAL-ir nerve fibers were traced to enter the pars distalis of the anterior pituitary from the stalk as well as from the meningeal sheath covering the upper part of the anterior pituitary. Numerous GAL-ir cells presented in the pars distalis and the pars intermedia of the adenohypophysis. In the dog pituitary, GAL-ir nerve fibers were mainly located in the tail part and some in oral region. A majority of GAL-ir nerve fibers were at the periphery of the gland, especially in the medial planes, although some could be found deep in the gland. They appeared in individual fibers or in patches. Many GAL-ir nerve fibers and fiber fascicles existed in the median eminence and the sheath covering the tail and the oral part of the pituitary.