Regulatory peptides: key factors in the control of bodily functions.

At the turn of the century Pavlov postulated the theory of "nervism," while Brown-Sequard put forward the idea that certain tissues of the body can release active substances capable of specifically affecting distant organs. BrownSequard's theory of "chemical messengers" was further supported by Bayliss and Starling, who in 1902 reproduced Pavlov's experiments on pancreatic secretion using extracts of denervated duodenum. In one afternoon Pavlov's Nobel prize winning ideas of neural control of bodily functions were swept away. Bayliss and Starling then proposed the word "hormone" (from the Greek word for "I arouse to activity") to describe the existence of blood borne chemical messengers acting at a distance. These two apparently antagonistic views, neural versus hormonal control of bodily functions, have recently been reconciled with the discovery that the same active principles (that is, regulatory peptides) can be produced and released by both endocrine and neural tissues and may act as circulating hormones, local regulators, neurotransmitters, or all of these. The term "regulatory peptide" has recently been proposed to describe active peptides capable of eliciting their effects in one or more of these three separate ways. Characteristics of regulatory peptides