Serotonin and Adrenals: Regulation of Functions, Regulation of Development.

Serotonin is not only a neurotransmitter but also an important humoral regulator of various physiological processes outside the central nervous system. In the last decade, the concept of local serotonergic systems in peripheral organs, where serotonin realizes its effects via autocrine/paracrine mechanisms, has been under development. Such local systems have already been described in the pancreas, thymus, mammary gland, and bone marrow. We consider that a similar local serotonergic system is also characteristic of the adrenal glands. These paired organs are a key component of the mammalian endocrine system, providing a complex physiological response to stress. The adrenal glands consist of two parts distinct in origin and function—the cortex and medulla—while serotonin plays an important role in regulating hormone secretion in both of these structures. This review is aimed at analyzing the structure of the local serotonergic system in the adrenal gland as well as its role both in the regulation of adrenal functions in adult animals and in the formation of adrenals in embryogenesis. Analysis of the available data suggests that local serotonergic systems makes an organ susceptible to fluctuations in the level of serotonin circulating in the blood at all stages of ontogenesis. Thus, local sensitivity to serotonin provides the possibility of systemic humoral coordination of the development and functioning of the adrenal glands and other peripheral organs. From this perspective, the importance of local serotoninergic systems for developmental biology and medicine becomes clear. [ABSTRACT FROM AUTHOR]