Neuroendocrinology

Abstract

Neuroendocrinology investigates interactions between the nervous and endocrine systems. The nervous system is composed of the brain, spinal cord, ganglia, and nerves, and neural cells communicate directly with one another (and with cells of sensory and effector tissues) by means of neurotransmitters. The endocrine system is composed of ductless glands that release hormones that act systemically. Neuroendocrinology therefore investigates reciprocal influences of local and widespread chemical signaling systems in animals. Research in neuroendocrinology historically examined several distinct but related processes. Secretion of neuropeptide releasing factors from the hypothalamus (neurosecretion) was found to control the pituitary gland, which, in turn, governs many endocrine functions. The pattern of neuropeptide secretion is pulsatile and characterized by circadian and ultradian variations. The nervous system directly regulates the pineal gland and adrenal medulla. Thyroid hormones, steroids, and peptide hormones have important feedback effects regulating the neural control of their release. Hormones clearly regulate development of the nervous system. A variety of adult brain systems are influenced by hormones, and behavioral neuroendocrinology has become a fertile area. Most recently, several classes of hormones, such as neurosteroids, have been found to be synthesized and have neurotransmitter-like actions within the brain, thus blurring the distinction between endocrine and neuronal signaling systems.