Galanin and the neuroendocrine axes.

Galanin has diverse physiological functions, including nociception, arousal/sleep regulation, cognition, and many aspects of neuroendocrine activities that are associated with feeding, energy metabolism, thermoregulation, osmotic and water balance, and reproduction. This review will provide a brief overview of galanin actions in some major neuroendocrine processes. Most of the recent data are about the role of galanin in the central regulation of food intake and energy metabolism, and to some extent, in the regulation of reproduction. It seems that galanin plays a modulatory rather than regulatory role in the central and peripheral branches of the neuroendocrine systems. In the hypothalamus, it functions as a neurotransmitter/neuromodulator. In the pituitary and the peripheral endocrine glands, it acts via its receptors (GALRs) in a paracrine/autocrine fashion. The development of new, selective and potent antagonists of GALRs should keep advancing our knowledge not only in the physiology but also the pathophysiology of galanin as well.