Morphometric and Functional Changes of Rat Pituitary Somatotropes and Lactotropes after Central Administration of Somatostatin

Abstract

This study examined effects of intracerebroventricularly (i.c.v.) administered somatostatin (SRIH-14 and SRIH-28) on growth and function of pituitary somatotropes (GH cells) and lactotropes (PRL cells). Male rats received three i.c.v. injections (1 microgram/5 microliters) of SRIH-14 or SRIH-28 every second day. Blood samples were collected for hormone assays and pituitaries were removed for histological and morphometric evaluation 5 days after the last i.c.v. treatment. Compared to control animals, SRIH treatment decreased (p < 0.05) pituitary weight and all morphometric measurements obtained in GH and PRL cells. Concentrations of serum growth hormone (GH) and prolactin (PRL) in both SRIH-treated groups were also lower (p < 0.05) than in control rats. These findings suggest that centrally administered somatostatin is specifically involved in the control of growth and secretory activity of GH and PRL cells. Thus, pharmacological manipulation of SRIH receptors reached from cerebrospinal fluid may alter systemic effects of GH and PRL.