Central GAB Aergic Neuroendocrine Regulations: Pharmacological and Morphological Evidence

Publisher Summary Within the conceptual framework of neurosecretion and of humoral hypothalamic control of adenohypophysis, numerous investigations have been carried out over the last decades aiming at: (a) the characterization and identification of the various hypophysiotropic factors secreted by the hypothalamus; (b) the understanding of the various mechanisms by which the release of neurosecretory substances could be regulated. That a neuroendocrine role could be played by gamma-aminobutyric acid (GABA), a recognized inhibitory transmitter in the central nervous system has been suggested by studies in which pharmacological manipulations of GABAergic transmission were accompanied by modification of various endocrine parameters. Even in the cases where consistent effects were reported, it still remains to be assessed whether these effects are physiologically meaningful or just represent a pharmacological curiosity. One way to provide another type of experimental data for GABAergic neuroendocrine regulation is to look for morphological evidence, i.e. to investigate whether or not GABAergic cells or terminals—here defined in a narrow sense as those that contain GABA markers—are actually localized at the presumed strategic sites for the suspected GABA-related controls. This chapter presents a short review of the advantages and drawbacks of the various markers available for GABAergic neurons and later presents findings of current study.