Gamma-aminobutyric acid (GABA): a para- and/or autocrine hormone in the pituitary

SPECIFIC AIMSThe neurotransmitter gamma-aminobutyric acid (GABA) plays an important role in the regulation of pituitary gland function, but details of the underlying mechanism are poorly understood. Here we identify novel intrapituitary sources of GABA and disclose the sites of its synthesis, storage, and the distribution of its receptors in the endocrine master gland, the pituitary.PRINCIPAL FINDINGS1. Synthesis and storage of GABA occurs in endocrine growth hormone (GH) -producing cells of the anterior lobe and POMC-producing cells of the intermediate lobe of the pituitaryUsing RT-PCR, in situ hybridization histochemistry, immunohistochemistry, and immunoelectron microscopy, the GABA-synthesizing enzyme GAD 67, the vesicular transporter VIAAT/VGAT, and GABA were detected in the rat and primate pituitary. Although GAD and VIAAT/VGAT were found in all of the endocrine cells of the intermediate lobe, they were present only in the GH-producing endocrine cells of the anterior lobe (Fig. 1⤻ ). Immunoelectron ...